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10. Pathology and Oncology MCQs

Practice Set 133 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 2641

Topic: 10. Pathology and Oncology

Which of the following is considered a critical error and potential absolute contraindication when planning and performing a biopsy for a suspected primary malignant bone tumor of the distal femur?

. Using a longitudinal incision rather than a transverse incision.
. Deflating the tourniquet before wound closure to ensure hemostasis.
. Utilizing a core needle biopsy instead of an open incisional biopsy.
. Placing the biopsy tract outside the planned definitive resection bed.
. Avoiding the use of an Esmarch bandage to exsanguinate the limb before tourniquet inflation.

Correct Answer & Explanation

. Using a longitudinal incision rather than a transverse incision.

Explanation

The biopsy tract must be excised en bloc with the tumor during the definitive resection. Therefore, placing the biopsy tract outside the planned definitive resection bed is a major error, potentially leading to tumor seeding into normal tissues and making limb salvage impossible. Longitudinal incisions should always be used. Tourniquets should not be exsanguinated with an Esmarch to prevent embolization, and should be deflated prior to closure to achieve meticulous hemostasis. Core needle biopsy is typically the preferred initial method.

Question 2642

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with progressive knee pain and swelling. Radiographs demonstrate a mixed lytic and sclerotic lesion in the distal femoral metaphysis with a Codman's triangle and 'sunburst' periosteal reaction. Biopsy confirms high-grade conventional osteosarcoma. Following neoadjuvant chemotherapy, what is the most important prognostic factor for long-term overall survival in this patient?

. The anatomic location of the tumor
. The specific histologic subtype of conventional osteosarcoma
. The degree of histologic tumor necrosis in the resection specimen
. The surgical margin status being wide versus radical
. The age of the patient at the time of diagnosis

Correct Answer & Explanation

. The anatomic location of the tumor

Explanation

In high-grade conventional osteosarcoma, the degree of tumor necrosis following neoadjuvant chemotherapy (evaluated by the Huvos grading system) is the single most significant prognostic indicator for long-term overall survival. Greater than 90% necrosis indicates a good response and is associated with significantly higher survival rates compared to less than 90% necrosis (poor responder). While achieving clear surgical margins is essential for minimizing local recurrence, systemic response to chemotherapy dictates overall survival.

Question 2643

Topic: 10. Pathology and Oncology

A 55-year-old man has an incidental finding of a proximal humerus lesion. Radiographs show a lytic lesion with 'popcorn' calcifications. MRI demonstrates endosteal scalloping greater than 2/3 of the cortical thickness and soft tissue extension. Core needle biopsy confirms a grade II (intermediate-grade) conventional chondrosarcoma. What is the most appropriate management strategy for this patient?

. Extended intralesional curettage with cryotherapy and cementing
. Wide surgical resection and limb reconstruction
. Primary radiation therapy
. Neoadjuvant chemotherapy followed by wide resection
. Observation with serial radiographs every 6 months

Correct Answer & Explanation

. Extended intralesional curettage with cryotherapy and cementing

Explanation

Intermediate (Grade II) and high-grade (Grade III) conventional chondrosarcomas are typically treated with wide surgical resection. They are relatively avascular and have poor replication rates, making them highly resistant to both standard chemotherapy and radiation. Intralesional curettage with local adjuvants (like cryotherapy, phenol, or bone cement) may be appropriate for selected low-grade (Grade I) chondrosarcomas of the appendicular skeleton. However, grade II tumors require en bloc resection with negative margins to prevent local recurrence.

Question 2644

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with a painful mass in the diaphysis of his femur. Imaging shows a permeative lesion with a distinct 'onion-skin' periosteal reaction. Biopsy reveals uniform small round blue cells. Cytogenetic analysis identifies a t(11;22) translocation. Which of the following fusion proteins is most likely produced as a result of this translocation?

. SYT-SSX
. EWS-FLI1
. TLS-CHOP
. PAX3-FKHR
. COL1A1-PDGFB

Correct Answer & Explanation

. SYT-SSX

Explanation

Ewing sarcoma is classically associated with the t(11;22)(q24;q12) translocation, which leads to the formation of the EWS-FLI1 fusion protein in approximately 85-90% of cases. The SYT-SSX fusion protein is associated with synovial sarcoma [t(X;18)]. TLS-CHOP (also known as FUS-DDIT3) is seen in myxoid liposarcoma [t(12;16)]. PAX3-FKHR is seen in alveolar rhabdomyosarcoma [t(2;13)]. COL1A1-PDGFB is associated with dermatofibrosarcoma protuberans [t(17;22)].

Question 2645

Topic: 10. Pathology and Oncology

When performing an incisional biopsy for a suspected malignant primary bone tumor of the distal femur, which of the following technical principles must be strictly adhered to in order to avoid compromising definitive limb-salvage surgery?

. The biopsy tract should be placed transversely to minimize tension on the skin closure.
. A tourniquet should be applied and exsanguinated with an Esmarch bandage prior to inflation.
. The biopsy should be performed strictly through the muscle belly rather than intermuscular intervals to limit compartmental contamination.
. Extensive subperiosteal dissection is necessary to obtain adequate margins for histologic review.
. The cortical window must be perfectly square to allow for an easy fit of the bone plug.

Correct Answer & Explanation

. The biopsy tract should be placed transversely to minimize tension on the skin closure.

Explanation

When performing an open biopsy for a suspected bone sarcoma, the biopsy tract must be planned so it can be completely excised en bloc during definitive resection. This requires a longitudinal incision (not transverse), avoiding neurovascular bundles, and performing the biopsy directly through a single muscle compartment (muscle belly) rather than contaminating intermuscular planes. Exsanguination with an Esmarch before tourniquet inflation is contraindicated as it may embolize tumor cells into the systemic circulation; gravity elevation should be used instead. The cortical window should be oval or perfectly round to minimize stress risers.

Question 2646

Topic: 10. Pathology and Oncology

A 15-year-old boy with a primary osteosarcoma of the proximal tibia undergoes 10 weeks of neoadjuvant chemotherapy followed by wide resection. What is the most important histologic prognostic factor evaluated at the time of definitive surgical resection?

. The number of mitotic figures per high-power field
. The percentage of tumor necrosis
. The degree of chondroblastic differentiation
. The presence of skip metastases in the diaphysis
. The thickness of the tumor pseudocapsule

Correct Answer & Explanation

. The number of mitotic figures per high-power field

Explanation

The most important histologic prognostic factor for overall survival in osteosarcoma after neoadjuvant chemotherapy is the percentage of tumor necrosis in the resected specimen, as described by the Huvos grading system. Greater than 90% necrosis (Huvos grade III or IV) indicates a good response to chemotherapy and is associated with a significantly better prognosis.

Question 2647

Topic: 10. Pathology and Oncology

A 28-year-old woman presents with a slowly enlarging, painless mass deep in her thigh. MRI shows a well-circumscribed, multilobulated mass with heterogeneous signal intensity on T2-weighted images ('triple signal' sign). Biopsy demonstrates a biphasic spindle cell and epithelial tumor. Which of the following immunohistochemical markers is most likely to be positive in this lesion?

. S-100
. Desmin
. Cytokeratin
. Myogenin
. CD34

Correct Answer & Explanation

. S-100

Explanation

The clinical and histologic description is highly characteristic of synovial sarcoma, which frequently presents as a deep soft-tissue mass in young adults, often near a joint (though rarely intra-articular). Histologically, it can be biphasic (spindle cells and epithelial cells) or monophasic. Both forms characteristically stain positive for epithelial markers such as cytokeratin (CK) and epithelial membrane antigen (EMA), distinguishing it from other sarcomas. S-100 is typically used for nerve sheath tumors; desmin and myogenin for rhabdomyosarcoma; and CD34 for solitary fibrous tumors.

Question 2648

Topic: Bone Tumors

Distinguishing a low-grade chondrosarcoma from a benign enchondroma can be challenging on imaging and histology. Which of the following clinical or radiographic features is most suggestive of a low-grade chondrosarcoma rather than an enchondroma?

. Heavily stippled calcifications within the medullary canal
. Lesion located in the short tubular bones of the hand
. Deep, unremitting pain not relieved by rest or NSAIDs
. Lesion size less than 3 cm
. Lack of endosteal scalloping

Correct Answer & Explanation

. Heavily stippled calcifications within the medullary canal

Explanation

Differentiating an enchondroma from a low-grade chondrosarcoma is notoriously difficult. Clinical and radiographic features that strongly favor chondrosarcoma include the presence of unremitting pain (especially at night) unrelated to mechanical activity, rapid growth, large size (>5 cm), deep endosteal scalloping (>2/3 of cortical thickness), cortical breakthrough, and a soft tissue mass. Enchondromas are typically asymptomatic (unless associated with a pathologic fracture), small, heavily calcified, and commonly found in the hands and feet.

Question 2649

Topic: 10. Pathology and Oncology

A 45-year-old patient with Neurofibromatosis type 1 (NF1) presents with rapid enlargement and new onset of pain in a long-standing thigh mass. MRI reveals a large, heterogeneous mass with irregular margins. A biopsy reveals high-grade spindle cells with increased mitoses and focal necrosis. Which of the following cellular mechanisms is most closely associated with the patient's underlying genetic syndrome?

. Mutation of the APC gene leading to beta-catenin accumulation
. Mutation of the TP53 gene leading to loss of cell cycle regulation
. Decreased neurofibromin leading to continuous Ras signaling activation
. Mutation in the NF2 gene leading to abnormal merlin protein
. Mutation in the EXT1 gene leading to abnormal heparan sulfate synthesis

Correct Answer & Explanation

. Mutation of the APC gene leading to beta-catenin accumulation

Explanation

The patient has Neurofibromatosis type 1 (NF1), an autosomal dominant condition caused by mutations in the NF1 gene on chromosome 17q11.2. The NF1 gene encodes neurofibromin, a tumor suppressor protein that acts as a GTPase-activating protein (GAP) to negatively regulate the Ras signaling pathway. Loss of neurofibromin leads to continuous Ras activation and uncontrolled cell proliferation. The rapid enlargement and pain in a pre-existing neurofibroma in an NF1 patient strongly suggests malignant peripheral nerve sheath tumor (MPNST) transformation.

Question 2650

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with an enlarging, painful mass in his left thigh over the past 3 months. Radiographs demonstrate a diaphyseal permeative lytic lesion with a lamellated periosteal reaction. Biopsy reveals uniform, small round blue cells with scant cytoplasm. Immunohistochemistry is strongly positive for CD99. Which of the following is the most common cytogenetic abnormality associated with this tumor?

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

Correct Answer & Explanation

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

Explanation

The patient's clinical presentation, imaging, and histology are highly characteristic of Ewing sarcoma, a malignant small round blue cell tumor. The most common chromosomal translocation associated with Ewing sarcoma is t(11;22)(q24;q12), which results in the EWSR1-FLI1 fusion gene (present in ~85% of cases). CD99 (MIC2) is a sensitive but non-specific surface marker strongly expressed in Ewing sarcoma. Translocation t(X;18) is associated with synovial sarcoma; t(9;22) with extraskeletal myxoid chondrosarcoma; t(12;16) with myxoid liposarcoma; and t(2;13) with alveolar rhabdomyosarcoma.

Question 2651

Topic: 10. Pathology and Oncology

A 45-year-old man has a large, deep soft-tissue mass in his anterior thigh. He is scheduled for an incisional biopsy. Which of the following is a critical principle to follow when performing an orthopedic oncology biopsy?

. The incision should be oriented transversely to align with Langer lines and maximize cosmetic outcomes.
. If a tourniquet is used, it should remain inflated until the wound is completely closed and a pressure dressing is applied.
. Meticulous hemostasis must be achieved prior to closure to prevent hematoma formation.
. The biopsy should be taken exclusively from the central area of the tumor to capture the highest grade of disease.
. Surgical drains, if used, should exit through a separate site in an adjacent uncontaminated compartment.

Correct Answer & Explanation

. The incision should be oriented transversely to align with Langer lines and maximize cosmetic outcomes.

Explanation

Meticulous hemostasis is a paramount principle of oncologic biopsies. A post-operative hematoma can spread tumor cells into adjacent tissue planes or compartments, thereby necessitating a much wider definitive resection. A longitudinal incision (not transverse) must be used so that the entire biopsy tract can be easily excised en bloc with the tumor during definitive surgery. If a tourniquet is used, it must be deflated prior to closure to ensure complete hemostasis. Biopsies should sample the periphery of the tumor because central areas are frequently necrotic and non-diagnostic. Any drains used should exit directly in line with the surgical incision to allow for subsequent en bloc excision of the drain tract.

Question 2652

Topic: 10. Pathology and Oncology

A 42-year-old man presents with a deep, painless, slow-growing mass in his thigh. MRI reveals a well-circumscribed, multilobular intramuscular mass with high signal intensity on T2-weighted images and interspersed thin fatty septa. Histologic evaluation of a biopsy specimen reveals proliferating lipoblasts and a prominent, delicate 'chicken-wire' capillary network within a myxoid background. Which of the following translocations is most characteristic of this lesion?

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

Correct Answer & Explanation

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

Explanation

The clinical, radiographic, and histologic findings describe a myxoid liposarcoma. This tumor is histologically characterized by a myxoid matrix, a plexiform ('chicken-wire') capillary network, and lipoblasts. The pathognomonic cytogenetic abnormality for myxoid liposarcoma is t(12;16)(q13;p11), which results in the FUS-DDIT3 fusion protein. Options A, C, D, and E refer to Ewing sarcoma, synovial sarcoma, extraskeletal myxoid chondrosarcoma, and alveolar rhabdomyosarcoma, respectively.

Question 2653

Topic: 10. Pathology and Oncology

A 15-year-old boy is diagnosed with high-grade, conventional, intramedullary osteosarcoma of the distal femur. He undergoes a standard protocol of neoadjuvant chemotherapy followed by surgical resection. Which of the following factors is considered the most significant prognostic indicator for his overall, long-term survival?

. The histologic subtype of the osteosarcoma (e.g., osteoblastic vs. chondroblastic)
. The initial volume of the tumor at presentation
. The degree of tumor necrosis observed in the definitive surgical resection specimen
. The specific type of surgical reconstruction utilized (e.g., endoprosthesis vs. allograft)
. The baseline serum alkaline phosphatase level

Correct Answer & Explanation

. The histologic subtype of the osteosarcoma (e.g., osteoblastic vs. chondroblastic)

Explanation

The percentage of tumor necrosis following neoadjuvant chemotherapy is the single most important prognostic factor for long-term survival in high-grade conventional osteosarcoma. A 'good response' is typically defined as >=90% tumor necrosis (Huvos Grade III or IV), which strongly correlates with improved disease-free and overall survival. While tumor size and elevated alkaline phosphatase have some prognostic value, histologic response to induction chemotherapy remains the most powerful predictor of outcome. The type of local reconstruction does not influence overall survival provided wide surgical margins are achieved.

Question 2654

Topic: 10. Pathology and Oncology

A 45-year-old man presents with a painful shoulder. Radiographs show a lytic lesion with chondroid matrix calcifications in the proximal humerus with endosteal scalloping involving greater than 2/3 of the cortical thickness. Biopsy confirms a low-grade cartilaginous tumor. Which of the following genetic mutations is most likely to be present in this patient's lesion?

. EXT1
. GNAS
. IDH1
. p53
. RB1

Correct Answer & Explanation

. EXT1

Explanation

Mutations in the isocitrate dehydrogenase 1 (IDH1) and IDH2 genes are highly prevalent in solitary enchondromas and conventional chondrosarcomas. These mutations lead to the accumulation of oncometabolites that drive tumorigenesis. EXT1 and EXT2 mutations are associated with multiple hereditary exostoses (osteochondromas). GNAS mutations are characteristic of fibrous dysplasia. Mutations in p53 and RB1 are frequently associated with osteosarcoma.

Question 2655

Topic: 10. Pathology and Oncology

A 15-year-old boy is diagnosed with conventional high-grade osteosarcoma of the distal femur. He undergoes 10 weeks of neoadjuvant chemotherapy followed by wide surgical resection. Pathologic examination of the resected specimen reveals 95% tumor necrosis. Which of the following statements is most accurate regarding his prognosis and management?

. Adjuvant chemotherapy can be safely omitted due to the excellent histologic response.
. His 5-year overall survival rate is significantly better than a patient demonstrating 80% tumor necrosis.
. Radiation therapy should be immediately added to his postoperative regimen.
. The risk of local recurrence is determined primarily by the percentage of tumor necrosis.
. He will require an immediate amputation if he develops pulmonary micrometastases.

Correct Answer & Explanation

. Adjuvant chemotherapy can be safely omitted due to the excellent histologic response.

Explanation

The degree of histologic tumor necrosis following neoadjuvant chemotherapy is one of the most reliable and important prognostic factors for overall survival in patients with osteosarcoma. A necrosis rate of 90% or greater designates the patient as a 'good responder' and is associated with a significantly better long-term survival rate compared to those with less than 90% necrosis ('poor responders'). Local recurrence is primarily dictated by the adequacy of surgical margins, not the necrosis percentage. Adjuvant chemotherapy remains standard of care regardless of the necrosis rate, and osteosarcoma is generally considered a radioresistant tumor.

Question 2656

Topic: 10. Pathology and Oncology

A 12-year-old boy presents with progressive thigh pain, night sweats, and a low-grade fever. Radiographs show a permeative, aggressive diaphyseal lesion in the femur with a multilamellated 'onion skin' periosteal reaction. Biopsy reveals sheets of uniform small round blue cells with scant cytoplasm. Cytogenetic analysis of this tumor is most likely to reveal which of the following chromosomal abnormalities?

. t(11;22)(q24;q12)
. t(X;18)(p11;q11)
. t(2;13)(q35;q14)
. t(12;16)(q13;p11)
. t(9;22)(q34;q11)

Correct Answer & Explanation

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

Explanation

Ewing sarcoma is a highly malignant bone tumor characterized histologically by small round blue cells and clinically by its diaphyseal location and 'onion skin' periostitis. It is most strongly associated with the t(11;22)(q24;q12) chromosomal translocation, resulting in the fusion of the EWSR1 gene on chromosome 22 with the FLI1 gene on chromosome 11. The t(X;18) translocation is pathognomonic for Synovial Sarcoma; t(2;13) for Alveolar Rhabdomyosarcoma; and t(12;16) for Myxoid Liposarcoma.

Question 2657

Topic: 10. Pathology and Oncology

A 15-year-old boy is diagnosed with high-grade intramedullary osteosarcoma of the proximal tibia. Genetic analysis of the resected tumor reveals a loss of heterozygosity in a specific gene. This gene normally functions as a tumor suppressor by halting the cell cycle at the G1/S checkpoint to allow for DNA repair, and germline mutations in this gene are associated with a syndrome that predisposes individuals to early-onset breast cancer, soft tissue sarcomas, and adrenocortical carcinomas. Which of the following genes is most likely mutated?

. Retinoblastoma (Rb)
. GNAS
. EXT1
. TP53
. RUNX2

Correct Answer & Explanation

. Retinoblastoma (Rb)

Explanation

The scenario describes Li-Fraumeni syndrome, an autosomal dominant disorder caused by a germline mutation in the TP53 gene. The p53 protein acts as a critical tumor suppressor by halting the cell cycle at the G1/S transition to allow DNA repair or by inducing apoptosis if the damage is irreparable. The Retinoblastoma (Rb) gene is also a tumor suppressor associated with osteosarcoma, but it primarily acts by binding E2F, and its germline mutation is associated with hereditary retinoblastoma, not Li-Fraumeni syndrome.

Question 2658

Topic: 10. Pathology and Oncology

A 55-year-old man presents with a 6-month history of a dull, aching pain in his right shoulder that is worse at night. Radiographs and an MRI are obtained, showing a permeative lytic lesion in the proximal humerus with popcorn-like intralesional calcifications and endosteal scalloping involving > 2/3 of the cortical thickness.

Core needle biopsy reveals atypical hyperchromatic chondrocytes with significant binucleation and a myxoid stroma. Which of the following is the most appropriate definitive management for this lesion?

. Intralesional curettage with phenol adjuvant
. Neoadjuvant chemotherapy followed by wide surgical resection
. Wide surgical resection
. Definitive external beam radiation therapy
. Observation with serial radiographs every 6 months

Correct Answer & Explanation

. Intralesional curettage with phenol adjuvant

Explanation

The clinical, radiographic, and histologic findings are diagnostic of a conventional grade II or III chondrosarcoma. Endosteal scalloping > 2/3 of the cortical thickness and the presence of pain are critical radiographic and clinical discriminators differentiating it from a benign enchondroma. Because conventional chondrosarcomas are notoriously resistant to both chemotherapy and radiation therapy, wide surgical resection with negative margins is the mainstay of treatment. Intralesional curettage is only appropriate for atypical cartilaginous tumors/grade I chondrosarcomas in the appendicular skeleton.

Question 2659

Topic: 10. Pathology and Oncology

A 12-year-old boy presents with a 4-week history of worsening thigh pain, swelling, and low-grade fevers. A plain radiograph of the femur reveals a diaphyseal permeative destructive lesion with an 'onion-skin' periosteal reaction.

Biopsy demonstrates uniform, small round blue cells that strongly stain for CD99. The most common cytogenetic abnormality associated with this tumor results in a fusion gene involving which of the following chromosomes?

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

Correct Answer & Explanation

. t(11;22)

Explanation

The clinical presentation, radiographic 'onion-skin' (lamellated) periosteal reaction, and histologic finding of CD99-positive small round blue cells are diagnostic of Ewing Sarcoma. The hallmark cytogenetic abnormality in >90% of Ewing sarcomas is the t(11;22)(q24;q12) translocation, which fuses the EWS gene on chromosome 22 with the FLI1 gene on chromosome 11. t(X;18) is seen in synovial sarcoma. t(16;17) is seen in aneurysmal bone cysts. t(9;22) is the Philadelphia chromosome seen in CML, and t(12;16) is seen in myxoid liposarcoma.

Question 2660

Topic: 10. Pathology and Oncology

A 16-year-old girl is undergoing treatment for a conventional high-grade osteosarcoma of the distal femur. After completing her course of neoadjuvant chemotherapy, she undergoes wide surgical resection of the tumor.

Which of the following parameters evaluated on the final surgical pathology specimen is considered the most significant prognostic factor for her long-term overall survival?

. Mitotic index of the surviving tumor cells
. Presence of an intense lymphocytic infiltrate
. Percentage of tumor necrosis
. Degree of chondroblastic matrix production
. Proximity of the tumor margin to the neurovascular bundle

Correct Answer & Explanation

. Mitotic index of the surviving tumor cells

Explanation

The most important histologic prognostic factor for patients with conventional high-grade osteosarcoma following neoadjuvant chemotherapy is the percentage of tumor necrosis in the resected specimen, often graded by the Huvos grading system. A good response is defined as 90% or greater tumor necrosis, which strongly correlates with improved long-term, disease-free, and overall survival. While surgical margins are critical for local control, the chemotherapeutic response (necrosis percentage) reflects systemic disease control and overall prognosis.

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