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10. Pathology and Oncology MCQs

Practice Set 254 of 351

This practice set contains high-yield board review questions covering key concepts in 10. Pathology and Oncology. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 5061

Topic: Bone Tumors

A 15-year-old boy has an osteochondroma of the distal radius causing ulnar deviation of the hand and wrist. What is the most appropriate surgical approach to address this angular deformity?

. Simple excision of the osteochondroma with no further intervention
. Osteochondroma excision followed by contralateral growth plate stimulation
. Osteochondroma excision combined with corrective osteotomy and possibly guided growth
. Observation until skeletal maturity, then excision
. Amputation of the affected limb

Correct Answer & Explanation

. Osteochondroma excision combined with corrective osteotomy and possibly guided growth

Explanation

When an osteochondroma causes significant angular deformity, especially in a skeletally immature patient, simple excision may not correct the existing deformity. The most appropriate approach often involves excision of the osteochondroma combined with a corrective osteotomy and potentially guided growth (e.g., hemiepiphysiodesis) to address the underlying physeal disturbance and realign the limb. Observation will allow the deformity to worsen. Amputation is extreme. Contralateral growth plate stimulation is not the primary treatment for ipsilateral deformity correction.

Question 5062

Topic: 10. Pathology and Oncology

Which of the following conditions is most likely to be confused with a pedunculated osteochondroma on plain radiographs, requiring further imaging for differentiation?

. Enchondroma
. Osteoid osteoma
. Juxtacortical chondroma
. Parosteal osteosarcoma
. Non-ossifying fibroma

Correct Answer & Explanation

. Parosteal osteosarcoma

Explanation

Parosteal osteosarcoma can often be confused with a sessile osteochondroma on plain radiographs, as both are surface lesions with a bony component. However, parosteal osteosarcoma typically shows a clear cleavage plane between the tumor and the cortex, without continuity of the medullary cavity, and often has a more aggressive periosteal reaction or 'string sign.' Further imaging like CT or MRI can highlight these differences and rule out malignant features. Enchondroma and non-ossifying fibroma are intramedullary. Osteoid osteoma is typically small and purely cortical. Juxtacortical chondroma is a purely cartilaginous surface lesion.

Question 5063

Topic: 10. Pathology and Oncology

What is the most accurate statement regarding the incidence of osteochondromas?

. They are the most common primary malignant bone tumor.
. They are the most common primary benign bone tumor.
. They are less common than enchondromas.
. They primarily affect individuals over 60 years of age.
. They are more common in females than males.

Correct Answer & Explanation

. They are the most common primary benign bone tumor.

Explanation

Osteochondromas are indeed the most common primary benign bone tumor, accounting for 35-50% of all benign bone tumors and 10-15% of all bone tumors. They are not malignant. They are more common than enchondromas and typically affect children and adolescents, often becoming quiescent after skeletal maturity. There is a slight male predominance.

Question 5064

Topic: Bone Tumors

What is the typical direction of growth for a pedunculated osteochondroma relative to the adjacent joint?

. Towards the joint
. Parallel to the joint surface
. Away from the joint
. Variable, no typical direction
. Into the joint space

Correct Answer & Explanation

. Away from the joint

Explanation

A classic feature of osteochondromas is that they typically point or grow away from the adjacent joint. This is thought to be due to the migration of physeal cartilage cells away from the growth plate in the direction of muscle pull or fascial attachments. This orientation helps differentiate it from other lesions.

Question 5065

Topic: 10. Pathology and Oncology

An 8-year-old child presents with an asymptomatic osteochondroma of the proximal tibia. What is the most common reason for considering surgical intervention in such a case, assuming no malignant features?

. To prevent future malignant transformation
. To correct an existing or impending angular deformity or limb length discrepancy
. To alleviate anxiety of the parents
. To improve cosmetic appearance
. To rule out other benign conditions

Correct Answer & Explanation

. To correct an existing or impending angular deformity or limb length discrepancy

Explanation

In skeletally immature patients, even if asymptomatic, a common indication for surgical intervention of an osteochondroma, especially those near the physis, is to correct or prevent the progression of an angular deformity (e.g., genu valgum/varus) or a limb length discrepancy, which can arise from asymmetric physeal growth disturbance. Malignant transformation is exceedingly rare in children. The other options are less significant clinical indications for surgery.

Question 5066

Topic: 10. Pathology and Oncology

Which of the following radiological findings is LEAST suggestive of malignant transformation of an osteochondroma?

. Increased cartilage cap thickness (>2 cm in adults)
. New pain or rapid increase in size after skeletal maturity
. Erosion of the adjacent bone
. Presence of a clear stalk continuous with the parent bone
. Irregular or ill-defined margins of the lesion

Correct Answer & Explanation

. Presence of a clear stalk continuous with the parent bone

Explanation

The presence of a clear stalk continuous with the parent bone is a characteristic feature of a benign osteochondroma and does not suggest malignant transformation. In fact, it's a diagnostic feature of the benign lesion. All other options (increased cartilage cap thickness, new pain/rapid growth in adulthood, erosion of adjacent bone, irregular margins) are strong indicators of potential malignant transformation to a secondary peripheral chondrosarcoma.

Question 5067

Topic: Bone Tumors

What type of cartilage typically forms the cap of an osteochondroma?

. Fibrocartilage
. Elastic cartilage
. Hyaline cartilage
. Articular cartilage
. Reticular cartilage

Correct Answer & Explanation

. Hyaline cartilage

Explanation

The cartilage cap of an osteochondroma is composed of hyaline cartilage, which is structurally and functionally similar to the growth plate cartilage. This cap is responsible for the continued growth of the osteochondroma. Fibrocartilage is found in menisci or intervertebral discs. Elastic cartilage is found in the ear. Articular cartilage lines joints. Reticular cartilage is not a recognized type.

Question 5068

Topic: Bone Tumors

A 10-year-old child presents with a fixed bony mass near the ankle. MRI reveals an osteochondroma arising from the distal tibia, with a cartilage cap of 1 cm. There are no signs of compression or pain. What is the recommended follow-up interval?

. Every 3 months until skeletal maturity
. Annual clinical and radiographic follow-up until skeletal maturity
. No further follow-up is necessary
. MRI every 6 months
. Immediate surgical consultation

Correct Answer & Explanation

. Annual clinical and radiographic follow-up until skeletal maturity

Explanation

For an asymptomatic osteochondroma in a skeletally immature patient, observation with annual clinical and radiographic follow-up is generally recommended until skeletal maturity. This allows for monitoring of growth, development of symptoms, or angular deformities. More frequent imaging (MRI every 6 months) is usually reserved for suspicious lesions. No further follow-up is inappropriate. Immediate surgical consultation is not needed for asymptomatic lesions.

Question 5069

Topic: Bone Tumors

Which of the following is considered a 'secondary' osteochondroma?

. A solitary osteochondroma occurring de novo
. An osteochondroma associated with Hereditary Multiple Exostoses (HME)
. An osteochondroma that has undergone malignant transformation into chondrosarcoma
. An osteochondroma arising after radiation therapy
. A subungual exostosis

Correct Answer & Explanation

. An osteochondroma that has undergone malignant transformation into chondrosarcoma

Explanation

The term 'secondary osteochondroma' is not a standard classification. However, an osteochondroma that has undergone malignant transformation to a chondrosarcoma is termed a 'secondary peripheral chondrosarcoma' (secondary, as it arose from a pre-existing lesion). The question implies this context. HME lesions are primary congenital lesions. Post-radiation lesions are 'radiation-induced exostoses'. Subungual exostosis is a specific type of osteochondroma. The most 'secondary' process among the options is the malignant change.

Question 5070

Topic: Bone Tumors

A 13-year-old female presents with a painful osteochondroma of the distal femur that impinges on the vastus medialis muscle during knee flexion. Which of the following is the most appropriate treatment?

. Physical therapy to improve flexibility
. NSAIDs and activity modification
. Surgical excision of the osteochondroma
. Steroid injection into the lesion
. Observation until skeletal maturity

Correct Answer & Explanation

. Surgical excision of the osteochondroma

Explanation

When an osteochondroma causes mechanical symptoms such as muscle impingement and pain during movement, surgical excision is the definitive treatment. Conservative measures like physical therapy, NSAIDs, or steroid injections are unlikely to resolve mechanical impingement. Observation would allow symptoms to persist or worsen. Surgical excision relieves the mechanical obstruction.

Question 5071

Topic: 10. Pathology and Oncology

What percentage of solitary osteochondromas are estimated to undergo malignant transformation?

. Less than 1%
. 2-5%
. 5-10%
. 10-15%
. More than 20%

Correct Answer & Explanation

. Less than 1%

Explanation

The risk of malignant transformation for a solitary osteochondroma is very low, generally estimated to be less than 1%. This contrasts with Hereditary Multiple Exostoses, where the risk is significantly higher (5-25%).

Question 5072

Topic: Bone Tumors

Which part of the body is LEAST commonly affected by osteochondromas?

. Distal femur
. Proximal tibia
. Proximal humerus
. Skull
. Pelvis

Correct Answer & Explanation

. Skull

Explanation

Osteochondromas most commonly occur in the metaphysis of long bones, particularly around the knee (distal femur, proximal tibia) and shoulder (proximal humerus). They can also occur in flat bones such as the pelvis, scapula, and ribs. They are exceedingly rare in the skull, as the skull bones develop from intramembranous ossification, not endochondral ossification from a growth plate.

Question 5073

Topic: Bone Tumors

What term describes the characteristic appearance of an osteochondroma on plain radiographs where the cortex and medullary cavity of the exostosis are continuous with the parent bone?

. Ground glass appearance
. Onion skinning
. Continuity sign
. Codman's triangle
. Soap bubble appearance

Correct Answer & Explanation

. Continuity sign

Explanation

The 'continuity sign' or 'medullary continuity' refers to the pathognomonic radiographic feature of an osteochondroma where the cortex and medullary cavity of the exostosis are directly continuous with those of the underlying parent bone. Ground glass is fibrous dysplasia. Onion skinning is Ewing sarcoma. Codman's triangle is a periosteal reaction. Soap bubble appearance can be seen in ABC or giant cell tumor.

Question 5074

Topic: Bone Tumors

A 17-year-old male with a history of HME presents with an osteochondroma causing impingement on the adjacent ulna, leading to forearm rotation limitation. Which surgical principle is paramount for preventing recurrence and effectively addressing the impingement?

. Curettage of the cartilage cap
. Complete excision of the osteochondroma including its cartilage cap and perichondrium
. Partial excision to preserve the growth plate
. Radiation therapy to shrink the lesion
. Internal fixation of the lesion

Correct Answer & Explanation

. Complete excision of the osteochondroma including its cartilage cap and perichondrium

Explanation

For effective treatment of a symptomatic osteochondroma and to minimize recurrence, complete surgical excision of the entire osteochondroma, including its cartilage cap and any associated perichondrium (especially if near a joint or growth plate), is crucial. Incomplete removal of the cartilage cap is a common cause of recurrence. Curettage alone is insufficient. Partial excision is prone to recurrence. Radiation and internal fixation are not indicated.

Question 5075

Topic: 10. Pathology and Oncology

Which of the following describes the typical growth pattern of an osteochondroma?

. Rapidly invasive growth throughout life
. Slow growth, typically stopping at skeletal maturity
. Growth that accelerates after skeletal maturity
. Growth independent of the adjacent growth plate
. Cycles of growth and regression throughout childhood

Correct Answer & Explanation

. Slow growth, typically stopping at skeletal maturity

Explanation

Osteochondromas typically grow slowly during childhood, mimicking the growth of the adjacent growth plate. Their growth usually ceases with the closure of the adjacent physis at skeletal maturity. Any growth or enlargement after skeletal maturity, particularly if accompanied by pain, raises suspicion for malignant transformation. Rapid invasive growth or cycles of regression are not typical.

Question 5076

Topic: 10. Pathology and Oncology

What is the primary role of Computed Tomography (CT) in the evaluation of an osteochondroma?

. To assess cartilage cap thickness
. To evaluate neurovascular compression
. To delineate the bony morphology and continuity with the parent bone
. To detect marrow edema suggestive of inflammation
. To confirm the diagnosis of malignant transformation

Correct Answer & Explanation

. To delineate the bony morphology and continuity with the parent bone

Explanation

CT imaging is excellent for precisely delineating the bony morphology of the osteochondroma and, crucially, confirming the continuity of its cortical and medullary bone with the parent bone. This is a key diagnostic feature. While MRI is superior for cartilage cap thickness and neurovascular structures, and biopsy confirms malignancy, CT excels at bone detail.

Question 5077

Topic: 10. Pathology and Oncology

A 9-year-old boy presents with an osteochondroma of the distal tibia. His parents are worried about potential malignant transformation. What is the approximate risk of malignant transformation in a child of this age?

. Less than 0.1%
. 1-2%
. 5-10%
. 15-20%
. Greater than 25%

Correct Answer & Explanation

. Less than 0.1%

Explanation

Malignant transformation of osteochondromas is exceedingly rare in children before skeletal maturity. The vast majority of secondary chondrosarcomas develop in adults, typically in their 3rd to 5th decades. Therefore, the risk in a 9-year-old is extremely low, generally considered less than 0.1% for a solitary lesion.

Question 5078

Topic: 10. Pathology and Oncology

Which term is often used interchangeably with osteochondroma?

. Enchondroma
. Exostosis
. Chondroblastoma
. Non-ossifying fibroma
. Osteosarcoma

Correct Answer & Explanation

. Exostosis

Explanation

Osteochondroma is often referred to as an 'exostosis' (specifically, osteocartilaginous exostosis) due to its bony outgrowth nature. While exostosis is a broader term for any bony outgrowth, in the context of bone tumors, it frequently refers to osteochondromas. The other terms refer to different types of bone lesions (enchondroma: intramedullary cartilage; chondroblastoma: epiphyseal cartilage; non-ossifying fibroma: fibrous lesion; osteosarcoma: malignant bone-forming tumor).

Question 5079

Topic: 10. Pathology and Oncology

A patient with HME reports persistent, localized tenderness and warmth over a large, sessile osteochondroma in the posterior thigh. There is no significant increase in mass size. What initial conservative measure is most appropriate?

. Surgical excision
. MRI with contrast for malignancy workup
. NSAIDs and activity modification
. Percutaneous biopsy
. Radiation therapy

Correct Answer & Explanation

. NSAIDs and activity modification

Explanation

Given the persistent localized tenderness and warmth without significant mass enlargement, symptomatic bursitis secondary to the osteochondroma is a strong possibility. Initial conservative management with NSAIDs and activity modification is appropriate. If symptoms persist or worsen, further imaging like MRI might be warranted, but it's not the immediate first step unless there is suspicion of malignancy (which is less likely without significant growth).

Question 5080

Topic: Bone Tumors

Which of the following is a key distinguishing feature between an osteochondroma and a parosteal osteosarcoma on MRI?

. Signal intensity on T1-weighted images
. Presence of a cartilage cap
. Periosteal reaction patterns
. Continuity of the medullary bone with the parent cortex
. Presence of fatty marrow within the lesion

Correct Answer & Explanation

. Continuity of the medullary bone with the parent cortex

Explanation

While both can be surface lesions, the critical differentiating factor, especially evident on MRI, is the continuity of the medullary bone of the lesion with the parent bone in an osteochondroma. Parosteal osteosarcoma typically has a clear cleavage plane between the tumor and the underlying cortex, and there is no medullary continuity. A cartilage cap is unique to osteochondroma. Fatty marrow can be present in both, but its continuity is key. Periosteal reaction can be variable. Signal intensity alone is not definitive.

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