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10. Pathology and Oncology MCQs

Practice Set 131 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 2601

Topic: 10. Pathology and Oncology

A 35-year-old woman presents with a painless mass on the posterior aspect of her distal thigh. Radiographs

demonstrate a dense, heavily ossified, broad-based mass attached to the posterior cortex of the distal femur with a 'string sign' radiolucency. Biopsy reveals well-differentiated bone trabeculae within a low-grade fibroblastic stroma. Which of the following is true regarding this diagnosis?

. It typically arises within the medullary canal.
. It is associated with MDM2 and CDK4 gene amplifications.
. Standard treatment includes neoadjuvant chemotherapy followed by wide resection.
. It has a higher propensity for early pulmonary metastasis than classic conventional osteosarcoma.
. The characteristic radiographic appearance is entirely lytic with fluid-fluid levels.

Correct Answer & Explanation

. It typically arises within the medullary canal.

Explanation

The clinical scenario describes a parosteal osteosarcoma, a low-grade, surface-based osteosarcoma typically found on the posterior aspect of the distal femur. It characteristically exhibits amplification of the MDM2 and CDK4 genes on chromosome 12q13-15. Because it is a low-grade malignancy, the primary treatment is wide surgical resection without systemic chemotherapy (unless dedifferentiated). It carries an excellent prognosis with a low risk of metastasis compared to conventional osteosarcoma.

Question 2602

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with fever, weight loss, and progressive pain in his left mid-thigh. Radiographs

show a destructive, permeative diaphyseal lesion with a large soft tissue extension and an 'onion-skin' periosteal reaction. Histological examination reveals sheets of uniform, small, round blue cells that strongly express membranous CD99. What is the most important initial step in the systemic staging of this patient?

. PET-CT scan to evaluate for multicentric contiguous disease
. Sentinel lymph node biopsy
. Whole-body MRI for skip lesions
. CT scan of the chest and bone marrow aspiration/biopsy
. Measurement of serum alkaline phosphatase and lactate dehydrogenase (LDH)

Correct Answer & Explanation

. PET-CT scan to evaluate for multicentric contiguous disease

Explanation

The presentation and pathology are diagnostic of Ewing sarcoma. Staging for Ewing sarcoma must rule out metastases, which most commonly occur in the lungs, other bones, and the bone marrow. Therefore, a CT scan of the chest and bone marrow aspirates/biopsies (often bilateral) are the most critical components of the initial staging workup to identify systemic disease spread. CD99 is a sensitive marker for Ewing sarcoma.

Question 2603

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with an expanding, painful mass in the diaphysis of his left femur. Radiographs display an aggressive, permeative osteolytic lesion with a 'laminated' (onion-skin) periosteal reaction. Core needle biopsy reveals sheets of uniform, small round blue cells with scant cytoplasm. Immunohistochemical staining is strongly positive for CD99. Which of the following chromosomal translocations is most characteristic of this diagnosis?

. t(X;18)(p11;q11)
. t(11;22)(q24;q12)
. t(2;13)(q35;q14)
. t(9;22)(q22;q12)
. t(12;16)(q13;p11)

Correct Answer & Explanation

. t(X;18)(p11;q11)

Explanation

The clinical presentation, radiographic findings ('onion-skin' laminated periosteal reaction), and histopathology (small round blue cells, strong CD99 positivity) are highly characteristic of Ewing sarcoma. The hallmark genetic abnormality in Ewing sarcoma is a balanced chromosomal translocation, most commonly t(11;22)(q24;q12), which results in the fusion of the EWS gene on chromosome 22 with the FLI1 gene on chromosome 11. In contrast, t(X;18) is associated with synovial sarcoma; t(2;13) is seen in alveolar rhabdomyosarcoma; t(9;22) in bone/soft tissue tumors often characterizes extraskeletal myxoid chondrosarcoma; and t(12;16) is associated with myxoid liposarcoma.

Question 2604

Topic: 10. Pathology and Oncology

A 24-year-old man presents with a slow-growing, painful mass around his knee. An MRI reveals a soft tissue mass near the joint but not within the joint cavity. Core needle biopsy demonstrates a biphasic pattern consisting of epithelial and spindle cells. Which of the following cytogenetic translocations is most characteristic of this tumor?

. t(11;22)(q24;q12)
. t(X;18)(p11;q11)
. t(12;16)(q13;p11)
. t(2;13)(q35;q14)
. t(9;22)(q22;q12)

Correct Answer & Explanation

. t(11;22)(q24;q12)

Explanation

The patient has a synovial sarcoma, which typically presents in young adults as a slow-growing soft tissue mass near large joints, most commonly the knee. The characteristic genetic abnormality is the translocation t(X;18)(p11;q11), resulting in the SS18-SSX fusion gene. This fusion protein disrupts gene expression and drives oncogenesis. The other translocations are associated with Ewing sarcoma (t(11;22)), myxoid liposarcoma (t(12;16)), alveolar rhabdomyosarcoma (t(2;13)), and extraskeletal myxoid chondrosarcoma (t(9;22)).

Question 2605

Topic: 10. Pathology and Oncology

A 45-year-old woman is incidentally found to have a destructive lesion in her distal femur on plain radiographs. She is scheduled to undergo a core needle biopsy. Which of the following is an essential orthopedic oncology principle when performing a biopsy for a suspected primary bone sarcoma?

. The biopsy tract should be placed transversely across the limb to avoid major vascular bundles.
. The biopsy should be performed through the muscle belly rather than through the muscle-tendon junction.
. The biopsy tract must be planned so that it can be completely excised en bloc during definitive tumor resection.
. Tourniquets should be routinely used and strict exsanguination performed prior to inflation to maintain a bloodless field.
. Core needle biopsy is generally contraindicated for suspected primary malignant bone tumors due to a high risk of sampling error.

Correct Answer & Explanation

. The biopsy tract should be placed transversely across the limb to avoid major vascular bundles.

Explanation

A critical principle of biopsy for suspected sarcomas is that the biopsy tract is considered contaminated with tumor cells. Therefore, it must be carefully planned longitudinally so that the entire tract can be completely excised en bloc with the tumor during the definitive surgical resection. Transverse incisions complicate future en bloc resection. Exsanguination with an Esmarch bandage should be avoided to prevent tumor embolization; if a tourniquet is used, the limb should only be elevated. Core needle biopsies are the standard of care due to high accuracy and minimal morbidity.

Question 2606

Topic: 10. Pathology and Oncology

A 14-year-old boy is diagnosed with high-grade conventional osteosarcoma of the proximal tibia. He completes neoadjuvant chemotherapy and undergoes wide surgical resection. Which of the following represents the most reliable prognostic factor for his overall long-term survival?

. Percentage of tumor necrosis in the surgical resection specimen
. Size of the primary tumor at initial clinical presentation
. Histological subtype of osteosarcoma (e.g., osteoblastic vs. chondroblastic)
. Serum alkaline phosphatase level at initial presentation
. Surgical margin status after resection

Correct Answer & Explanation

. Percentage of tumor necrosis in the surgical resection specimen

Explanation

The most important prognostic factor for overall survival in patients with high-grade conventional osteosarcoma is the histological response to neoadjuvant chemotherapy, which is measured by the percentage of tumor necrosis in the resected specimen (Huvos grading system). Greater than 90% necrosis indicates a good chemotherapeutic response and is associated with significantly better long-term survival rates. While surgical margin status is critical for local tumor control, chemotherapy response is the primary predictor of systemic microscopic disease eradication and overall survival.

Question 2607

Topic: 10. Pathology and Oncology

A 35-year-old man presents with chronic hip pain. Plain radiographs reveal a well-defined lytic lesion localized to the proximal femoral epiphysis. A biopsy demonstrates sheets of cells with clear, vacuolated cytoplasm and distinct cell membranes, interspersed with prominent trabeculae of reactive woven bone. What is the most appropriate definitive management for this lesion?

. Intralesional curettage with high-speed burring and polymethylmethacrylate (PMMA) augmentation
. Wide en bloc resection and endoprosthetic reconstruction
. Neoadjuvant systemic chemotherapy followed by wide surgical resection
. Primary fractionated radiation therapy
. Radiofrequency ablation

Correct Answer & Explanation

. Intralesional curettage with high-speed burring and polymethylmethacrylate (PMMA) augmentation

Explanation

The clinical presentation (epiphyseal lesion in an adult) and histology (clear cells, woven bone) are classic for clear cell chondrosarcoma. Unlike conventional chondrosarcomas, which rarely involve the epiphysis, clear cell chondrosarcomas are typically epiphyseal. They are low-grade malignant bone tumors. The treatment of choice is wide en bloc resection. Intralesional curettage has an unacceptably high local recurrence rate for clear cell chondrosarcoma. Like most chondrosarcomas, they are relatively resistant to both systemic chemotherapy and radiation therapy.

Question 2608

Topic: 10. Pathology and Oncology

A 40-year-old man undergoes excision of a deep, painless soft tissue mass in his medial thigh. Pathological analysis reveals a prominent myxoid stroma, a delicate arborizing 'chicken-wire' capillary network, and scattered lipoblasts. Which of the following genetic abnormalities is most characteristic of this soft tissue tumor?

. t(11;22) EWSR1-FLI1
. t(X;18) SS18-SSX
. t(12;16) FUS-DDIT3
. t(2;13) PAX3-FOXO1
. MDM2 gene amplification

Correct Answer & Explanation

. t(11;22) EWSR1-FLI1

Explanation

The histological description of a myxoid stroma, chicken-wire vascular pattern, and lipoblasts is pathognomonic for myxoid liposarcoma. The hallmark translocation for myxoid liposarcoma is t(12;16)(q13;p11), which results in the FUS-DDIT3 (formerly FUS-CHOP) fusion gene. MDM2 amplification is characteristic of well-differentiated and dedifferentiated liposarcomas. The other translocations correspond to Ewing sarcoma (EWSR1-FLI1), synovial sarcoma (SS18-SSX), and alveolar rhabdomyosarcoma (PAX3-FOXO1).

Question 2609

Topic: 10. Pathology and Oncology

A 12-year-old girl presents with a rapidly enlarging mass in her proximal humerus. Plain radiographs show an expansile, multiloculated, radiolucent lesion with a 'soap bubble' appearance and a thin cortical shell. A biopsy is performed. Which of the following histological findings is most characteristic of this specific lesion?

. Cavernous, blood-filled spaces completely lacking an endothelial lining
. Sheets of atypical plasma cells with prominent nucleoli and 'clock-face' chromatin
. A biphasic pattern consisting of intermingling spindle cells and epithelial elements
. Small round blue cells arranged in classic Homer-Wright rosettes
. Atypical lobules of cartilage demonstrating prominent myxoid matrix changes

Correct Answer & Explanation

. Cavernous, blood-filled spaces completely lacking an endothelial lining

Explanation

The clinical and radiographic presentation is highly consistent with an aneurysmal bone cyst (ABC). Histologically, ABCs are characterized by cavernous, blood-filled spaces that are separated by fibrous septa containing fibroblasts, osteoclast-like giant cells, and reactive woven bone. Crucially, these blood-filled spaces lack a true endothelial lining, which differentiates them morphologically from true vascular tumors such as hemangiomas or angiosarcomas.

Question 2610

Topic: 10. Pathology and Oncology

A 55-year-old man presents with generalized diffuse bone pain and profound proximal muscle weakness. Laboratory studies show severe hypophosphatemia, low 1,25-dihydroxyvitamin D levels, and elevated alkaline phosphatase. Serum calcium and parathyroid hormone levels are normal. A full-body MRI reveals a small, benign-appearing soft tissue mass in the plantar aspect of his foot. Excision of this mass is most likely to result in which of the following physiological changes?

. Normalization of serum calcium levels
. Resolution of hypophosphatemia and normalization of phosphate handling
. A significant decrease in serum parathyroid hormone levels
. An increase in serum Fibroblast Growth Factor 23 (FGF-23) levels
. Development of post-operative hypercalcemia

Correct Answer & Explanation

. Normalization of serum calcium levels

Explanation

The patient is presenting with tumor-induced osteomalacia (TIO), an acquired paraneoplastic syndrome typically caused by a small, benign phosphaturic mesenchymal tumor (PMT). These tumors autonomously secrete fibroblast growth factor 23 (FGF-23). Excess FGF-23 inhibits renal proximal tubule phosphate reabsorption (causing phosphaturia and hypophosphatemia) and suppresses 1-alpha-hydroxylase (decreasing 1,25-dihydroxyvitamin D synthesis). Surgical excision of the causative tumor leads to a rapid decline in FGF-23, which results in the prompt resolution of hypophosphatemia and normalization of bone mineralization.

Question 2611

Topic: Bone Tumors

A 10-year-old boy presents with multiple painless, hard bony bumps around his knees and ankles. Radiographs demonstrate multiple sessile and pedunculated osteochondromas pointing away from the adjacent joints. He is clinically diagnosed with multiple hereditary exostoses (MHE). Loss-of-function mutations in which of the following genes are responsible for this autosomal dominant condition?

. NF1 and NF2
. EXT1 and EXT2
. RB1 and TP53
. GNAS
. APC

Correct Answer & Explanation

. NF1 and NF2

Explanation

Multiple hereditary exostoses (MHE), also known as multiple osteochondromatosis, is an autosomal dominant skeletal disorder caused by loss-of-function mutations in the tumor suppressor genes EXT1 or EXT2. These genes encode glycosyltransferases that are essential for the synthesis of heparan sulfate. A deficiency in heparan sulfate disrupts the Indian hedgehog (Ihh) signaling pathway at the physis, leading to ectopic cartilage growth and osteochondroma formation. NF genes cause neurofibromatosis, RB1/TP53 mutations are seen in osteosarcoma, GNAS mutations cause fibrous dysplasia, and APC mutations cause familial adenomatous polyposis.

Question 2612

Topic: 10. Pathology and Oncology

A 15-year-old boy is diagnosed with high-grade intramedullary osteosarcoma of the proximal tibia. He undergoes 10 weeks of neoadjuvant chemotherapy with methotrexate, doxorubicin, and cisplatin, followed by wide surgical resection. Pathologic evaluation of the resected specimen is performed. Which of the following is the most important prognostic factor for his overall survival?

. Presence of skip metastases
. Distance of the tumor from the joint line
. Percentage of tumor necrosis in the resection specimen
. Tumor size at initial presentation
. Alkaline phosphatase levels post-resection

Correct Answer & Explanation

. Presence of skip metastases

Explanation

The most important prognostic factor for overall survival in a patient with high-grade osteosarcoma treated with neoadjuvant chemotherapy is the histologic response to the chemotherapy. This is measured as the percentage of tumor necrosis in the definitive resection specimen. A "good response" is typically defined as greater than 90% tumor necrosis (Huvos grade III or IV) and correlates with significantly improved disease-free and overall survival rates.

Question 2613

Topic: 10. Pathology and Oncology

A 28-year-old man presents with a slow-growing, deep-seated soft tissue mass near his knee joint. An MRI demonstrates a heterogeneous mass adjacent to the capsule but not within the joint space. Core needle biopsy shows a biphasic tumor with both epithelial and spindle cell components. Which of the following cytogenetic translocations is most characteristic of this diagnosis?

. t(11;22)(q24;q12)
. t(12;16)(q13;p11)
. t(9;22)(q22;q12)
. t(2;13)(q35;q14)
. t(X;18)(p11;q11)

Correct Answer & Explanation

. t(11;22)(q24;q12)

Explanation

The patient's clinical presentation, MRI findings, and biphasic histology (epithelial and spindle cells) are highly characteristic of Synovial Sarcoma. Synovial sarcoma is characterized by the cytogenetic translocation t(X;18)(p11;q11), which results in the SYT-SSX fusion gene. Option A refers to Ewing Sarcoma. Option B is Myxoid Liposarcoma. Option C is Extraskeletal Myxoid Chondrosarcoma. Option D is Alveolar Rhabdomyosarcoma.

Question 2614

Topic: 10. Pathology and Oncology

A 16-year-old boy complains of chronic, aching shoulder pain. Radiographs show a well-circumscribed lytic lesion in the epiphysis of the proximal humerus with a thin sclerotic rim. MRI reveals extensive surrounding bone marrow edema. Histological examination of a biopsy specimen demonstrates sheets of mononuclear cells with grooved nuclei and areas of pericellular 'chicken-wire' calcification. What is the most appropriate definitive treatment for this lesion?

. Wide en bloc resection
. Intralesional curettage and bone grafting
. Preoperative radiation followed by marginal excision
. Chemotherapy alone
. Observation and NSAIDs

Correct Answer & Explanation

. Wide en bloc resection

Explanation

The clinical, radiographic, and histologic findings (epiphyseal location, grooved 'coffee-bean' nuclei, and 'chicken-wire' calcification) are pathognomonic for a Chondroblastoma. Chondroblastoma is a benign but locally aggressive cartilaginous tumor. The gold standard treatment is extended intralesional curettage (often utilizing a high-speed burr or chemical adjuvants) followed by bone grafting or PMMA cementation. Wide resection is overly aggressive for this benign lesion, and observation is inappropriate given its locally destructive nature.

Question 2615

Topic: 10. Pathology and Oncology

A 19-year-old man presents with severe mid-back pain that awakens him at night and is dramatically relieved by ibuprofen. A CT scan of the spine shows a 1.2-cm radiolucent nidus with surrounding sclerosis in the posterior elements of L3. The exquisite pain caused by this lesion is primarily mediated by the local overproduction of which of the following substances?

. Interleukin-1 (IL-1)
. Substance P
. Tumor necrosis factor alpha (TNF-alpha)
. Prostaglandin E2 (PGE2)
. Bradykinin

Correct Answer & Explanation

. Interleukin-1 (IL-1)

Explanation

The clinical presentation of severe night pain relieved by NSAIDs and the CT finding of a sclerotic lesion with a central radiolucent nidus in the posterior elements of the spine are classic for an Osteoid Osteoma. The profound pain associated with this benign bone tumor is due to the overproduction of prostaglandins, specifically Prostaglandin E2 (PGE2), by the nidus via increased expression of cyclooxygenase-2 (COX-2).

Question 2616

Topic: 10. Pathology and Oncology

A 45-year-old woman is found to have an aggressive, bone-destructive lesion in the distal femur. A biopsy is planned. Which of the following statements regarding the principles of orthopedic oncologic biopsy is most accurate?

. Transverse incisions are preferred on the extremities to minimize skin tension.
. A tourniquet should be inflated and exsanguination performed using an Esmarch bandage prior to the incision.
. A drain, if used, should be brought out through a separate incision far from the biopsy tract.
. Intramedullary plugging after bone window creation is contraindicated.
. The biopsy tract must be planned so it can be excised entirely during the definitive resection.

Correct Answer & Explanation

. Transverse incisions are preferred on the extremities to minimize skin tension.

Explanation

Strict adherence to oncologic biopsy principles is mandatory to avoid tumor dissemination and limb compromise. The biopsy tract must be placed longitudinally and in line with the planned definitive resection so that it can be completely excised. Transverse incisions contaminate multiple compartments. Exsanguination with an Esmarch bandage is contraindicated as it may push tumor cells systemically; only elevation should be used before tourniquet inflation. Drains should exit near the wound, in line with the incision. Cortical windows should be plugged (e.g., with PMMA) to prevent tumor hematoma tracking.

Question 2617

Topic: 10. Pathology and Oncology

A 50-year-old man presents with a large, painless mass in his posterior thigh. MRI shows a multilobulated soft-tissue mass with high signal intensity on T2-weighted images and a cystic-like appearance, though it enhances with gadolinium. Biopsy reveals a prominent plexiform capillary network and lipoblasts in a myxoid stroma. Which of the following features is most unique to the management or behavior of this specific sarcoma subtype?

. It is notoriously resistant to radiation therapy.
. Amputation is the standard of care due to frequent local recurrence.
. It has a high propensity for extrapulmonary bone metastases, particularly to the spine.
. It frequently presents with severe, burning radicular pain.
. Sentinel lymph node biopsy is routinely required.

Correct Answer & Explanation

. It is notoriously resistant to radiation therapy.

Explanation

The pathology describes a Myxoid Liposarcoma, classically presenting with a prominent plexiform capillary network ('crow's feet' vessels) and t(12;16) FUS-DDIT3 translocation. A unique behavioral characteristic of myxoid liposarcoma is its strong propensity to metastasize to extrapulmonary sites, particularly the skeletal system (especially the spine), often before pulmonary metastases occur. Consequently, staging typically requires full-spine MRI. It is also exceptionally sensitive to radiation therapy, contrary to Option A.

Question 2618

Topic: 10. Pathology and Oncology

A 40-year-old man undergoes curettage of a lytic lesion in the proximal femoral epiphysis. The lesion was initially thought to be a chondroblastoma based on its location. However, definitive histopathology reveals large cells with abundant clear cytoplasm, distinct cytoplasmic membranes, and central nuclei, interspersed with areas of conventional hyaline cartilage and reactive woven bone. What is the most appropriate next step in management?

. Systemic chemotherapy
. Local radiation therapy
. Wide surgical resection
. Radiofrequency ablation
. Observation

Correct Answer & Explanation

. Systemic chemotherapy

Explanation

The histopathology and clinical scenario describe a Clear Cell Chondrosarcoma. This low-grade malignant cartilage tumor frequently involves the epiphysis, mimicking a benign chondroblastoma radiographically. However, clear cell chondrosarcoma tends to occur in an older age group (30-50 years) compared to chondroblastoma (teens). Because it is a malignant tumor, intralesional curettage alone results in a very high recurrence rate. The standard of care is wide en bloc surgical resection.

Question 2619

Topic: 10. Pathology and Oncology

A 25-year-old woman presents with a slow-growing, painless mass deep in the thigh. MRI shows a highly vascular lesion with prominent peritumoral flow voids. Chest CT reveals bilateral small pulmonary nodules, and a brain MRI shows a single contrast-enhancing lesion. Biopsy of the thigh mass reveals large, polygonal cells arranged in a nested pattern with central loss of cellular cohesion. What is the characteristic chromosomal translocation associated with this condition?

. t(11;22)
. t(X;18)
. t(9;22)
. der(17)t(X;17)
. t(12;16)

Correct Answer & Explanation

. t(11;22)

Explanation

The clinical picture describes Alveolar Soft Part Sarcoma (ASPS). ASPS typically presents in young adults as a deep-seated thigh mass. It is notorious for its highly vascular nature and an extremely high rate of early metastases to the lungs and brain, underscoring the need for brain MRI during staging. Pathologically, it features nested, polygonal cells with loss of central cohesion (pseudoalveolar pattern). It is characterized by the unbalanced translocation der(17)t(X;17)(p11;q25), resulting in the ASPSCR1-TFE3 fusion.

Question 2620

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with a painful, swollen distal femur. Imaging shows a sunburst periosteal reaction. Biopsy reveals malignant spindle cells producing osteoid. Mutation of which of the following tumor suppressor genes is most commonly implicated in the pathogenesis of this disease?

. TP53 and RB1
. EXT1 and EXT2
. GNAS
. RUNX2
. COL1A1

Correct Answer & Explanation

. TP53 and RB1

Explanation

The patient has osteosarcoma, which is characterized by the production of malignant osteoid. The pathogenesis is strongly associated with mutations in the tumor suppressor genes TP53 (associated with Li-Fraumeni syndrome) and RB1 (associated with hereditary retinoblastoma). EXT1 and EXT2 mutations are seen in multiple hereditary exostoses. GNAS mutations are associated with fibrous dysplasia. RUNX2 is a transcription factor essential for osteoblast differentiation, frequently involved in cleidocranial dysplasia.

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