ABOS Orthopedic Board Review: Primary Bone Tumors, Chondromas, & MSK Pathology | Part 9

Correct Answer: C

Rationale: Charcot arthropathy is characterized by severe joint destruction, fragmentation, and disorganization that is often disproportionately painless due to the underlying neuropathy. The text describes "destroyed humeral head and disorganized gleno-humeral joint" and "extensive soft tissue ossification." While osteoarthritis can have osteophytes, joint space narrowing, and subchondral cysts, it is typically painful and does not usually present with the extreme disorganization and instability seen in Charcot joints, especially with minimal pain. Symmetrical involvement is more characteristic of inflammatory arthropathies like rheumatoid arthritis, not typically Charcot.

Correct Answer: C

Rationale: The text states, "Bone tumors account for 0.2–0.5% of all malignant tumors," indicating their relative uncommonness. Option B is incorrect as it underestimates the stated range.

Correct Answer: C

Rationale: The text explicitly states, "Most of them are highly malignant." Option A is incorrect as it contradicts the malignant nature described.

Correct Answer: D

Rationale: The text notes that primary bone neoplasms "aff ect children frequently." Option A is incorrect as it misrepresents the common age group affected.

Correct Answer: D

Rationale: The text states, "the primary fi lter is the lung followed by other parts of the skeleton." Option A is incorrect as regional lymph nodes are rarely affected.

Correct Answer: C

Rationale: The text specifies the metastatic pathway as "the primary fi lter is the lung followed by other parts of the skeleton." Option A is incorrect as regional lymph nodes are rarely affected.

Correct Answer: C

Rationale: The text explicitly states, "Regional lymph nodes are rarely aff ected" in the context of metastasis from primary bone neoplasms. Option A is incorrect as it directly contradicts the provided information.

Correct Answer: B

Rationale: The text states, "they show up as characteristic lesions in the radiographs." Option A is incorrect as it describes a non-specific or different radiographic pattern.

Correct Answer: C

Rationale: The text explains, "Bone neoplasms change or destroy the structure of the bone, and accordingly they show up as characteristic lesions in the radiographs." Option B is incorrect as it only describes one potential aspect (bone formation) and not the primary mechanism of structural change/destruction.

Correct Answer: C

Rationale: The text states, "As clinical features such as pain, swelling and discomfort are nonspecifi c..." Option A is incorrect as it directly contradicts the text.

Correct Answer: D

Rationale: The text explains, "As clinical features such as pain, swelling and discomfort are nonspecifi c, a long period of time may elapse until the correct diagnosis is achieved." Option B is incorrect as specific clinical features would lead to earlier diagnosis, not delay.

Correct Answer: C

Rationale: The text states, "most of the bone sarcomas are recognized in an extracompartmental advanced stage." Option A is incorrect as it describes an early stage, contrary to the text.

Correct Answer: D

Rationale: The text states, "Th e pathway of metastasis formation is diff erent from that of carcinoma, the primary fi lter is the lung followed by other parts of the skeleton." This explicitly describes the pathway for bone neoplasms, highlighting the lung as the primary filter, which is presented as a difference from carcinoma. Option B is incorrect as regional lymph nodes are rarely affected by primary bone neoplasms.

Correct Answer: C

Rationale: The text states, "Most of them are highly malignant." Option A is incorrect as it contradicts this statement.

Correct Answer: C

Rationale: The text states, "Bone neoplasms change or destroy the structure of the bone." Option B is incorrect as it only describes one potential aspect and not the overall impact of changing or destroying the structure.

Correct Answer: C

Rationale: The text states, "As consequence, most of the bone sarcomas are recognized in an extracompartmental advanced stage." This is a direct consequence of the diagnostic delay. Option B is incorrect as delayed diagnosis leads to later stage recognition.

Correct Answer: C

Rationale: The text states that primary bone neoplasms "aff ect children frequently." Option A is incorrect as it directly contradicts this statement.

Correct Answer: C

Rationale: The text states, "they show up as characteristic lesions in the radiographs." Option B is incorrect as radiographs provide characteristic, not just nonspecific, findings.

Correct Answer: C

Rationale: The text states, "As clinical features such as pain, swelling and discomfort are nonspecifi c..." Option A is incorrect as it contradicts the text.

Correct Answer: C

Rationale: The text explicitly states, "Regional lymph nodes are rarely aff ected" in the context of metastasis from primary bone neoplasms. Option B is incorrect as it directly contradicts the provided information.

Correct Answer: B

Rationale: The text states, "Bone tumors account for 0.2–0.5% of all malignant tumors." Option A is incorrect as it underestimates the stated range.

Correct Answer: C

Rationale: The provided text states that "Bone tumors account for 0.2–0.5% of all malignant tumors," indicating their relative uncommonness. Main Distractor: Option D suggests a higher incidence than stated in the text, which could be confused if the exact percentage is not recalled.

Correct Answer: B

Rationale: The text explicitly states, "Most of them are highly malignant and affect children frequently." Main Distractor: Option A is incorrect as the text highlights the high malignancy and frequent occurrence in children, directly contradicting the idea of benignity and elderly affection.

Correct Answer: D

Rationale: The text states, "The pathway of metastasis formation is different from that of carcinoma, the primary filter is the lung followed by other parts of the skeleton." This refers to the metastasis of bone neoplasms themselves. Main Distractor: Option A (regional lymph nodes) is incorrect because the text explicitly states that "Regional lymph nodes are rarely affected."

Correct Answer: E

Rationale: The text specifies, "the primary filter is the lung followed by other parts of the skeleton." Main Distractor: Option A (regional lymph nodes) is incorrect as the text states they are "rarely affected."

Correct Answer: C

Rationale: The text explicitly states, "Regional lymph nodes are rarely affected" in the context of metastasis from bone neoplasms. Main Distractor: Option B is incorrect because the text indicates rare involvement, not frequent, and the lung is the primary filter.

Correct Answer: C

Rationale: The text states, "Bone neoplasms change or destroy the structure of the bone, and accordingly they show up as characteristic lesions in the radiographs." Main Distractor: Option D is incorrect because while some lesions can be sclerotic, the text emphasizes "change or destroy the structure," which is broader than just sclerotic and implies disruption, not intact architecture.

Correct Answer: C

Rationale: The text explicitly states, "As clinical features such as pain, swelling and discomfort are nonspecific..." Main Distractor: Option A is incorrect because the text clearly states the features are "nonspecific," which directly contradicts the idea of high specificity and early diagnosis.

Correct Answer: B

Rationale: The text states, "As clinical features such as pain, swelling and discomfort are nonspecific, a long period of time may elapse until the correct diagnosis is achieved." Main Distractor: Option E is incorrect because the nonspecific nature of symptoms leads to delayed diagnosis, not early detection or screening.

Correct Answer: C

Rationale: The text concludes, "As consequence, most of the bone sarcomas are recognized in an extracompartmental advanced stage." Main Distractor: Option B is incorrect because the text explicitly states "extracompartmental advanced stage," indicating a later and more extensive presentation than an early, localized stage.

Correct Answer: B

Rationale: The text states, "Bone tumors account for 0.2–0.5% of all malignant tumors." Main Distractor: Option C suggests a significantly higher prevalence than what is stated in the text, making it a plausible but incorrect guess if the exact figure is not known.

Correct Answer: C

Rationale: The text explicitly states, "The pathway of metastasis formation is different from that of carcinoma, the primary filter is the lung followed by other parts of the skeleton." Main Distractor: Option A directly contradicts the text's assertion that the pathway is "different from that of carcinoma."

Correct Answer: C

Rationale: The text states, "Bone neoplasms change or destroy the structure of the bone..." Main Distractor: Option E is incorrect because while some lesions can be sclerotic, the overall description is "change or destroy," implying disruption rather than uniform increase in density.

Correct Answer: B

Rationale: The text states, "Bone neoplasms change or destroy the structure of the bone, and accordingly they show up as characteristic lesions in the radiographs." Main Distractor: Option A is incorrect because the text describes them as "characteristic lesions," implying distinct and recognizable patterns, not subtle or indistinct changes.

Correct Answer: C

Rationale: The text states, "As clinical features such as pain, swelling and discomfort are nonspecific, a long period of time may elapse until the correct diagnosis is achieved." Main Distractor: Option E is incorrect because while early lesions can be subtle, the text specifically attributes the delay to the *nonspecificity of clinical features*, not solely the limitations of radiographs.

Correct Answer: C

Rationale: The term "extracompartmental" implies that the tumor has grown beyond the confines of the bone or its original anatomical compartment, which is consistent with an "advanced stage" as described in the text. Main Distractor: Option A is incorrect as "extracompartmental" directly contradicts the idea of the tumor being confined within the bone.

Correct Answer: C

Rationale: The text states, "Most of them are highly malignant and affect children frequently." Main Distractor: Option A is incorrect as it directly contradicts the text's description of most bone tumors being "highly malignant."

Correct Answer: D

Rationale: The text states, "the primary filter is the lung followed by other parts of the skeleton" for metastasis formation from bone neoplasms. Main Distractor: Option A (liver) is a common site for metastasis from other primary cancers but is not identified as the primary filter for bone neoplasms in the provided text.

Correct Answer: D

Rationale: The text states, "the primary filter is the lung followed by other parts of the skeleton." Main Distractor: Option C (regional lymph nodes) is incorrect as the text states they are "rarely affected."

Correct Answer: C

Rationale: The text explicitly states, "As clinical features such as pain, swelling and discomfort are nonspecific..." Main Distractor: Option A is incorrect because the text directly contradicts this by stating the features are "nonspecific."

Correct Answer: C

Rationale: Periosteal chondromas are benign intracortical cartilaginous lesions that arise from the periosteum, matching the clinical and histological description. Enchondromas are intramedullary, osteochondromas have a bony stalk, chondrosarcomas are malignant, and fibrous dysplasia is a fibro-osseous lesion.

Correct Answer: B

Rationale: The teaching case states that the majority of patients with periosteal chondromas present within the second through the fourth decades of life. The patient's age of 25 falls squarely within this range.

Correct Answer: C

Rationale: The teaching case explicitly states, "Most patients are asymptomatic." While large lesions may cause mechanical symptoms, small to moderate-sized lesions are typically discovered incidentally.

Correct Answer: C

Rationale: Fig. 8.27 and its accompanying text state that the gross specimen of a periosteal chondroma "resembles hyaline cartilage."

Correct Answer: B

Rationale: Fig. 8.28 and its description indicate that "Periosteal chondromas are typically more cellular than their intramedullary counterparts." This increased cellularity is a key distinguishing feature.

Correct Answer: C

Rationale: Fig. 8.29 and its caption state that periosteal chondromas "often display a lobular growth pattern." This is a characteristic histological feature.

Correct Answer: C

Rationale: The teaching case defines periosteal chondromas as "benign intracortical cartilaginous lesions." The description of eroding the outer cortex is consistent with an intracortical location.

Correct Answer: C

Rationale: The teaching case mentions, "Lesions that become especially large may cause local mechanical symptoms or bursitis." A 6 cm lesion would be considered "especially large."

Correct Answer: C

Rationale: The teaching case states, "Depending on the size of the lesion and the patient’s body habitus, lesions may be palpated on physical examination." Body habitus directly affects the ability to palpate superficial masses.

Correct Answer: C

Rationale: Periosteal chondromas are defined as "intracortical" lesions, meaning they are located within the cortex, often juxtacortical. Enchondromas, in contrast, are intramedullary (within the medullary cavity). This difference in location is the primary distinguishing feature on imaging.

Correct Answer: C

Rationale: The teaching case clearly states, "Periosteal chondromas are benign intracortical cartilaginous lesions."

Correct Answer: C

Rationale: The teaching case highlights that "Periosteal chondromas are typically more cellular than their intramedullary counterparts." This increased cellularity is a diagnostic clue.

Correct Answer: C

Rationale: As a benign lesion, periosteal chondromas typically grow slowly. While most are asymptomatic, the text notes that "Lesions that become especially large may cause local mechanical symptoms or bursitis," implying a potential for symptoms with growth.

Correct Answer: C

Rationale: As a benign, intracortical cartilaginous lesion, a periosteal chondroma typically appears as a well-defined lucency (due to cartilage) located juxtacortically (periosteal/intracortical) with a sclerotic rim, indicating its benign and slow-growing nature. Other options describe aggressive or malignant bone lesions.

Correct Answer: D

Rationale: The term "periosteal" in "periosteal chondroma" directly indicates its origin from the periosteum, the membrane covering the outer surface of bones.

Correct Answer: C

Rationale: The caption for Fig. 8.27 explicitly states, "The lesion resembles hyaline cartilage," which is a key characteristic of its gross appearance.

Correct Answer: C

Rationale: The caption for Fig. 8.29 states, "They often

Question 57

A 33-year-old female undergoes surgical excision of a benign intracortical cartilaginous lesion from her femur. During gross examination, the pathologist notes the specimen's appearance. Which of the following best describes the gross appearance of a periosteal chondroma?

• A) A gritty, yellowish-white mass resembling fibrous tissue
• B) A soft, gelatinous mass with hemorrhagic areas
• C) A firm, bluish-white mass resembling hyaline cartilage
• D) A hard, ivory-like mass resembling cortical bone
• E) A cystic lesion filled with serous fluid

View Answer & Explanation

Correct Answer: C

Rationale: Fig. 8.27 and its caption state, "Periosteal chondroma gross specimen. The lesion resembles hyaline cartilage." Hyaline cartilage is typically firm and bluish-white. The other options describe different tissue types not characteristic of a chondroma.

Question 57

A 29-year-old male has a biopsy of a suspected periosteal chondroma from his tibia. Histopathological examination is performed. When comparing a periosteal chondroma to an intramedullary enchondroma, which microscopic feature is characteristic of the periosteal variant?

• A) Less cellularity
• B) More prominent myxoid change
• C) More cellularity
• D) Presence of osteoid formation
• E) Abundant fat cells

View Answer & Explanation

Correct Answer: C

Rationale: Fig. 8.28 and its caption state, "Periosteal chondromas are typically more cellular than their intramedullary counterparts." This is a key distinguishing microscopic feature. Less cellularity would be characteristic of a typical enchondroma, while osteoid formation or fat cells are not features of pure cartilaginous lesions.

Question 57

A 31-year-old female undergoes imaging for a suspected benign bone lesion. The radiologist notes an intracortical lesion with a cartilaginous matrix. Which growth pattern is frequently observed in periosteal chondromas?

• A) Diffuse infiltrative growth
• B) Spiculated, sunburst pattern
• C) Lobular growth pattern
• D) Onion-skinning appearance
• E) Central necrosis with peripheral calcification

View Answer & Explanation

Correct Answer: C

Rationale: Fig. 8.29 and its caption state, "They often display a lobular growth pattern, as shown in this example." This is a characteristic feature of cartilaginous tumors, including periosteal chondromas. The other options describe patterns seen in other bone tumors (e.g., osteosarcoma, Ewing sarcoma).

Question 57

A 26-year-old male undergoes biopsy for an intracortical lesion on his femur. The pathologist notes a cartilaginous lesion with increased cellularity compared to a typical enchondroma. This finding, in the context of a periosteal chondroma, is important because it:

• A) Indicates a high likelihood of malignant transformation.
• B) Is a normal variant for this benign lesion and should not be misinterpreted.
• C) Suggests an underlying systemic metabolic disorder.
• D) Points towards a diagnosis of osteosarcoma.
• E) Requires immediate chemotherapy due to aggressive nature.

View Answer & Explanation

Correct Answer: B

Rationale: The text and Fig. 8.28 state, "Periosteal chondromas are typically more cellular than their intramedullary counterparts." This increased cellularity is a known feature of periosteal chondromas and should not be misinterpreted as a sign of malignancy (like chondrosarcoma) if other benign features are present. It does not indicate malignant transformation, a metabolic disorder, or osteosarcoma, nor does it require chemotherapy.

Question 57

A 30-year-old patient presents with a palpable, non-tender lesion on the diaphysis of the tibia. Radiographs show a well-defined intracortical lesion. Gross examination of the excised specimen reveals a firm, bluish-white mass. This appearance is consistent with a matrix composed primarily of:

• A) Fibrous tissue
• B) Bone (osseous tissue)
• C) Hyaline cartilage
• D) Myxoid tissue
• E) Adipose tissue

View Answer & Explanation

Correct Answer: C

Rationale: The text and Fig. 8.27 state, "The lesion resembles hyaline cartilage." This is the defining matrix component of a chondroma. Fibrous, osseous, myxoid, or adipose tissue would indicate a different type of tumor or lesion.

Question 57

A 32-year-old female presents with a slowly growing mass on her proximal humerus. Radiographs show an intracortical lesion with a lobular appearance. Histological examination confirms a periosteal chondroma. The lobular growth pattern observed in this lesion is a characteristic feature of:

• A) Highly aggressive malignant tumors
• B) Cartilaginous tumors in general
• C) Fibrous lesions only
• D) Osteoblastic lesions only
• E) Inflammatory processes

View Answer & Explanation

Correct Answer: B

Rationale: Fig. 8.29 and its caption state, "They often display a lobular growth pattern, as shown in this example." This lobular architecture is a common and characteristic feature of cartilaginous tumors, both benign and malignant, as cartilage grows in discrete nodules or lobules. It is not specific to highly aggressive malignancies, fibrous lesions, osteoblastic lesions, or inflammatory processes.

Question 57

A 31-year-old male undergoes surgical removal of a periosteal chondroma from his humerus. The gross specimen is examined. Which of the following terms best describes the tissue type that the lesion resembles?

• A) Fibrocartilage
• B) Elastic cartilage
• C) Hyaline cartilage
• D) Dense fibrous connective tissue
• E) Cancellous bone

View Answer & Explanation

Correct Answer: C

Rationale: The text and Fig. 8.27 explicitly state, "The lesion resembles hyaline cartilage." This is the specific type of cartilage that periosteal chondromas are composed of and resemble grossly. Fibrocartilage, elastic cartilage, dense fibrous tissue, or cancellous bone are different tissue types.

Correct Answer: D

Rationale: Periosteal chondromas are benign intracortical cartilaginous lesions typically presenting in the second through fourth decades of life. They are often asymptomatic but can be palpable. The description of an "intracortical cartilaginous lesion" directly matches the definition of a periosteal chondroma. Enchondromas are intramedullary, osteochondromas are exostoses with a cartilage cap, chondrosarcomas are malignant, and fibrous dysplasia is a fibro-osseous lesion, none of which fit the "intracortical cartilaginous" description as precisely.

Correct Answer: C

Rationale: The text explicitly states, "Most patients are asymptomatic." While large lesions may cause local mechanical symptoms or bursitis, the most common presentation is without symptoms. Severe pain, pathologic fracture, rapid growth, or systemic symptoms are not typical for a benign periosteal chondroma.

Correct Answer: B

Rationale: The clinical context states, "The majority of the patients present within the second through the fourth decades of life." This makes option B the most accurate age range for typical presentation. Other age ranges are less common for this specific benign lesion.

Correct Answer: C

Rationale: The text states, "Depending on the size of the lesion and the patient’s body habitus, lesions may be palpated on physical examination." This implies that a sufficiently large lesion, especially in a superficial location (as an intracortical lesion can be), allows for palpation. Rapid inflammation, deep intramedullary location (it's intracortical), skin discoloration, or high vascularity are not described as primary reasons for palpability.

Correct Answer: C

Rationale: The text states, "Lesions that become especially large may cause local mechanical symptoms or bursitis." This directly describes the characteristic symptoms if a periosteal chondroma becomes symptomatic. Systemic symptoms, pathologic fracture, rapid pain increase, or neurovascular compromise are not typical for this benign lesion.

Correct Answer: C

Rationale: Fig. 8.27 and its caption state, "Periosteal chondroma gross specimen. The lesion resembles hyaline cartilage." Hyaline cartilage is typically firm and bluish-white. The other options describe different tissue types not characteristic of a chondroma.

Correct Answer: C

Rationale: Fig. 8.28 and its caption state, "Periosteal chondromas are typically more cellular than their intramedullary counterparts." This is a key distinguishing microscopic feature. Less cellularity would be characteristic of a typical enchondroma, while osteoid formation or fat cells are not features of pure cartilaginous lesions.

Correct Answer: C

Rationale: Fig. 8.29 and its caption state, "They often display a lobular growth pattern, as shown in this example." This is a characteristic feature of cartilaginous tumors, including periosteal chondromas. The other options describe patterns seen in other bone tumors (e.g., osteosarcoma, Ewing sarcoma).

Correct Answer: C

Rationale: The text explicitly defines periosteal chondromas as "benign intracortical cartilaginous lesions." While they arise from the periosteum, their growth pattern is into the cortex, making "intracortical" the most precise description of their location within the bone. Intramedullary refers to the marrow cavity, subperiosteal is beneath the periosteum but not necessarily within the cortex, and juxta-articular/epiphyseal refer to specific joint/bone end locations.

Correct Answer: B

Rationale: The text clearly states, "Periosteal chondromas are benign intracortical cartilaginous lesions." This confirms their nature as benign primary bone tumors. They are not malignant, metastatic, inflammatory, or purely developmental anomalies without neoplastic potential.

Correct Answer: B

Rationale: The text and Fig. 8.28 state, "Periosteal chondromas are typically more cellular than their intramedullary counterparts." This increased cellularity is a known feature of periosteal chondromas and should not be misinterpreted as a sign of malignancy (like chondrosarcoma) if other benign features are present. It does not indicate malignant transformation, a metabolic disorder, or osteosarcoma, nor does it require chemotherapy.

Correct Answer: C

Rationale: The text and Fig. 8.27 state, "The lesion resembles hyaline cartilage." This is the defining matrix component of a chondroma. Fibrous, osseous, myxoid, or adipose tissue would indicate a different type of tumor or lesion.

Correct Answer: D

Rationale: As periosteal chondromas are benign, aggressive treatments like radiation, wide en bloc resection, chemotherapy, or amputation are not indicated. For symptomatic lesions, local excision (marginal excision) is typically curative. For mild symptoms, activity modification and observation may be considered first. The text implies conservative management for asymptomatic lesions and local intervention for symptomatic ones, consistent with a benign tumor.

Correct Answer: B

Rationale: Fig. 8.29 and its caption state, "They often display a lobular growth pattern, as shown in this example." This lobular architecture is a common and characteristic feature of cartilaginous tumors, both benign and malignant, as cartilage grows in discrete nodules or lobules. It is not specific to highly aggressive malignancies, fibrous lesions, osteoblastic lesions, or inflammatory processes.

Correct Answer: C

Rationale: Periosteal chondromas are benign lesions. While the text doesn't explicitly state prognosis, the term "benign" implies an excellent prognosis with appropriate management (e.g., observation for asymptomatic lesions, local excision for symptomatic ones). Malignant transformation is rare, recurrence is uncommon after complete excision, and progressive growth leading to severe deformity or systemic spread is not characteristic of a benign chondroma.

Correct Answer: D

Rationale: Lobular growth, increased cellularity (compared to enchondroma), and resemblance to hyaline cartilage are all characteristic features of a benign periosteal chondroma as described in the text and images. The presence of permeative growth (infiltrative) and significant nuclear atypia would be highly suspicious for malignancy, such as a chondrosarcoma, and would differentiate it from a benign periosteal chondroma. Absence of mitotic figures is a feature of benign lesions.

Correct Answer: C

Rationale: The definition "benign intracortical cartilaginous lesions" means the lesion is situated within the cortical bone. It is not confined to the medullary cavity (intramedullary), nor has it necessarily eroded through the cortex into soft tissues (though it can expand). It does not arise from articular cartilage, and while it originates from the periosteum, its growth pattern is into the cortex, making "intracortical" the most accurate description of its location.

Correct Answer: C

Rationale: The text states, "Most patients are asymptomatic... Depending on the size of the lesion and the patient’s body habitus, lesions may be palpated on physical examination." This implies that the most common reason for presentation is the incidental discovery of a palpable mass, rather than severe pain, fracture, infection, or systemic symptoms, which are rare or atypical for this benign lesion.

Correct Answer: C

Rationale: Since periosteal chondromas are benign and "most patients are asymptomatic," observation with serial imaging is the most appropriate initial management for an asymptomatic lesion. Surgical excision is reserved for symptomatic lesions or those with concerning features. Radiation and chemotherapy are not indicated for benign lesions. Biopsy might be considered if the diagnosis is uncertain, but for a classic asymptomatic presentation, observation is often sufficient.

Correct Answer: B

Rationale: Enchondromas are described as relatively common benign intramedullary cartilaginous lesions. The other options describe different types of bone lesions that do not fit the fundamental nature of an enchondroma.

Correct Answer: C

Rationale: The text states that enchondromas "oft en are detected incidentally." While some can be painful, incidental detection is the most frequent mode of discovery.

Correct Answer: B

Rationale: The text explicitly states, "Th e peak age is the second decade" for enchondromas.

Correct Answer: D

Rationale: The text states, "Half of enchondromas occur in the short tubular bones of the hands and feet," making this the most common location.

Correct Answer: B

Rationale: The text specifies, "Half of enchondromas occur in the short tubular bones of the hands and feet followed by proximal humerus and proximal and distal femur." Therefore, the proximal humerus is the next most common location after the short tubular bones.

Correct Answer: C

Rationale: The text lists "proximal and distal femur" as common locations for enchondromas, following the short tubular bones and proximal humerus.

Correct Answer: C

Rationale: The text notes, "Some enchondromas are painful and appear more aggressive radiographically," indicating a possible symptomatic presentation.

Correct Answer: C

Rationale: The text states that even painful and radiographically aggressive lesions "still display the bland, benign histology typical of asymptomatic lesions."

Correct Answer: C

Rationale: The caption for Fig. 8.23 a, b explicitly states, "Low-power images demonstrate the lobular growth pattern... of enchondromas."

Correct Answer: C

Rationale: The caption for Fig. 8.23 a, b mentions the "hypocellular nature of enchondromas" as a characteristic feature.

Correct Answer: D

Rationale: The caption for Fig. 8.23 a, b states, "The nuclei are uniform," which is a key feature of benign enchondromas.

Correct Answer: C

Rationale: The clinical context for Fig. 8.22 a, b explicitly links the images to "Ollier’s disease," which is characterized by multiple enchondromas and associated skeletal deformities.

Correct Answer: B

Rationale: The clinical context for Fig. 8.22 a, b states, "Short stature and osseous deformity secondary to Ollier’s disease."

Correct Answer: B

Rationale: The clinical context for Fig. 8.22 a, b states, "Short stature and osseous deformity secondary to Ollier’s disease."

Correct Answer: C

Rationale: Low-power images of enchondromas demonstrate a lobular growth pattern and hypocellular nature. The nuclei are typically uniform, indicating a benign lesion. High cellularity, nuclear pleomorphism, atypical mitoses, infiltrative growth, osteoid matrix, necrosis, and hemorrhage are not characteristic of benign enchondromas. The provided image (Fig. 8.23) supports the description of lobular growth and uniform nuclei.

Correct Answer: C

Rationale: Enchondromas are common benign intramedullary cartilaginous lesions, with a peak age in the second decade. Half of enchondromas occur in the short tubular bones of the hands and feet, making this location and age highly suggestive of enchondroma. While other options are bone tumors, enchondroma fits the clinical and demographic profile best based on the provided text. Chondrosarcoma is less common in this age group and typically more aggressive.

Correct Answer: B

Rationale: The provided text states that the peak age for enchondromas is the second decade. This aligns with the patient's age in the vignette. Other age ranges are less common for the peak incidence.

Correct Answer: C

Rationale: The text states that enchondromas are "relatively common benign intramedullary cartilaginous lesions that often are detected incidentally." While some can be painful, the majority are asymptomatic. They are not typically aggressive, are found in other locations besides hands/feet, and pain does not always indicate malignancy, as some painful lesions still display benign histology.

Correct Answer: C

Rationale: The text explicitly states, "Some enchondromas are painful and appear more aggressive radiographically but still display the bland, benign histology typical of asymptomatic lesions." This directly addresses the scenario described in the vignette. The other options are incorrect interpretations based on the provided information.

Correct Answer: C

Rationale: The clinical context for Fig. 8.22 a, b explicitly states "Short stature and osseous deformity secondary to Ollier’s disease." Ollier's disease is characterized by multiple enchondromas, often leading to skeletal deformities and growth disturbances like short stature. Maffucci syndrome also involves multiple enchondromas but includes soft tissue hemangiomas, which are not mentioned. Multiple hereditary exostoses involve osteochondromas, not enchondromas. Fibrous dysplasia and Paget's disease are different bone disorders.

Correct Answer: C

Rationale: The clinical context for Fig. 8.22 a, b explicitly states "Short stature and osseous deformity secondary to Ollier’s disease." This directly answers the question about the characteristic skeletal manifestations. The other options describe features not associated with Ollier's disease in the provided text.

Correct Answer: C

Rationale: The text defines enchondromas as "relatively common benign intramedullary cartilaginous lesions." This directly matches option C. The other options describe different types of lesions that are not consistent with the definition of an enchondroma.

Correct Answer: C

Rationale: The text states that "Half of enchondromas occur in the short tubular bones of the hands and feet" and that they are "often detected incidentally." This makes enchondroma the most likely diagnosis for an incidental, benign-appearing lesion in a phalanx in a teenager. Osteoid osteoma typically causes pain, giant cell tumors are rare in phalanges and more aggressive, Ewing sarcoma is malignant, and chondroblastoma typically affects epiphyses.