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10. Pathology and Oncology MCQs

Practice Set 129 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 2561

Topic: 10. Pathology and Oncology

A 12-year-old male presents with increasing pain in his proximal humerus over several months, worse at night and relieved by NSAIDs. Radiographs show a lytic lesion with a central nidus in the metaphysis of the proximal humerus. What is the MOST likely diagnosis?

. Osteosarcoma
. Ewing's sarcoma
. Osteoid osteoma
. Chondroblastoma
. Unicameral bone cyst

Correct Answer & Explanation

. Osteosarcoma

Explanation

The classic presentation of a small lytic lesion with a central radiolucent nidus, nocturnal pain relieved by NSAIDs (especially aspirin), and presence in the metaphysis of long bones (like the proximal humerus) in an adolescent is highly characteristic of an osteoid osteoma. Osteosarcoma and Ewing's sarcoma are malignant tumors with more aggressive radiographic features and systemic symptoms. Chondroblastoma is an epiphyseal lesion. Unicameral bone cysts are typically asymptomatic until fractured, and do not present with a nidus or pain relieved by NSAIDs.

Question 2562

Topic: 10. Pathology and Oncology

A patient presents with signs of an impending pathological fracture in the femoral diaphysis due to metastatic disease. What is the most significant biomechanical factor predicting the risk of fracture in this scenario?

. Size of the lesion in the sagittal plane
. Location of the lesion (proximal vs. distal diaphysis)
. Presence of cortical involvement greater than 50% of the circumference
. Activity level of the patient
. Type of primary tumor

Correct Answer & Explanation

. Size of the lesion in the sagittal plane

Explanation

Cortical involvement exceeding 50% of the circumference (or 2.5 cm length) is a widely recognized critical threshold for impending pathological fracture risk, often prompting prophylactic fixation. While other factors contribute, the degree of cortical destruction is the most direct biomechanical indicator of structural compromise and increased risk of fracture. The Mirels' score incorporates this along with pain, lesion type, and size, but cortical involvement is key.

Question 2563

Topic: 10. Pathology and Oncology

Which type of biopsy is generally preferred for diagnosing a suspected soft tissue sarcoma due to its ability to provide sufficient tissue for grading and subtyping?

. Fine Needle Aspiration (FNA)
. Excisional biopsy
. Incisional biopsy
. Punch biopsy
. Frozen section biopsy

Correct Answer & Explanation

. Fine Needle Aspiration (FNA)

Explanation

An incisional biopsy (where a portion of the tumor is removed) is generally preferred for suspected soft tissue sarcomas. It provides an adequate amount of tissue for full histological analysis, including tumor grading, subtyping, and special stains, which are critical for treatment planning. FNA often provides insufficient tissue. Excisional biopsy might compromise subsequent definitive surgical margins if the diagnosis is malignant. Punch biopsy is usually too small for deep soft tissue tumors. Frozen section is for rapid intraoperative assessment, not definitive diagnosis.

Question 2564

Topic: 10. Pathology and Oncology

Which of the following statements regarding osteosarcoma is FALSE?

. It is the most common primary malignant bone tumor in children and adolescents.
. It typically arises in the metaphysis of long bones.
. It is characterized by the direct formation of osteoid or immature bone by malignant cells.
. Pulmonary metastasis is common.
. Radiation therapy is the primary treatment modality.

Correct Answer & Explanation

. It is the most common primary malignant bone tumor in children and adolescents.

Explanation

The primary treatment for osteosarcoma involves neoadjuvant chemotherapy, surgical resection (limb-sparing surgery when possible), and adjuvant chemotherapy. Osteosarcoma is generally radioresistant, and radiation therapy is typically reserved for unresectable tumors, positive margins, or palliation. All other statements are true: it is common in children/adolescents, metaphyseal, produces osteoid, and metastasizes to the lungs.

Question 2565

Topic: 10. Pathology and Oncology

What is the typical appearance of Ewing's sarcoma on plain radiographs?

. Soap-bubble appearance with internal septations
. Periosteal reaction described as 'sunburst' pattern
. Geographic lysis with sclerotic rim
. Onion-skinning (lamellated periosteal reaction)
. Matrix mineralization with 'popcorn' calcifications

Correct Answer & Explanation

. Soap-bubble appearance with internal septations

Explanation

Ewing's sarcoma is classically associated with an 'onion-skinning' or lamellated periosteal reaction, especially in the diaphysis of long bones. This pattern results from successive layers of new bone being laid down by the periosteum in response to tumor invasion. 'Sunburst' is more typical of osteosarcoma. 'Soap-bubble' is seen in giant cell tumor. 'Popcorn' calcifications are seen in enchondroma. Geographic lysis with a sclerotic rim suggests a benign lesion.

Question 2566

Topic: 10. Pathology and Oncology

A patient presents with a painful mass in the distal femur. Biopsy reveals chondrosarcoma. Which statement accurately describes this tumor?

. It is characterized by the production of osteoid by malignant cells.
. It is typically highly responsive to chemotherapy and radiation.
. It is a malignant tumor of cartilage-forming cells.
. It primarily affects children and adolescents.
. It most commonly metastasizes to the regional lymph nodes.

Correct Answer & Explanation

. It is characterized by the production of osteoid by malignant cells.

Explanation

Chondrosarcoma is a malignant tumor characterized by the production of cartilage matrix by malignant chondrocytes. It is generally resistant to chemotherapy and radiation, with surgical resection being the primary treatment. While some variants can occur in younger individuals, it primarily affects older adults (over 40-50 years). It typically metastasizes hematogenously, primarily to the lungs, rather than to regional lymph nodes.

Question 2567

Topic: 10. Pathology and Oncology

What is the primary characteristic that differentiates primary bone tumors from metastatic bone tumors on a population level?

. Primary tumors are typically lytic; metastatic tumors are typically blastic.
. Primary tumors are more common than metastatic tumors.
. Primary tumors usually present with systemic symptoms; metastatic tumors are often asymptomatic.
. Metastatic bone tumors are far more common than primary bone tumors.
. Primary tumors always have a clear margin; metastatic tumors have ill-defined margins.

Correct Answer & Explanation

. Primary tumors are typically lytic; metastatic tumors are typically blastic.

Explanation

Metastatic bone tumors are significantly more common than primary bone tumors, especially in adults. While primary bone tumors can be lytic or blastic (e.g., osteosarcoma is often blastic), and metastatic tumors can be both lytic (e.g., renal cell) or blastic (e.g., prostate), the prevalence difference is the most defining characteristic on a population level. Presentation and margin clarity vary for both.

Question 2568

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with a painful, destructive mass in his distal femur. Biopsy reveals a highly cellular tumor composed of small round blue cells. Cytogenetic analysis demonstrates a t(11;22) chromosomal translocation. Which fusion gene is most likely responsible for this tumor's pathogenesis?

. SYT-SSX1
. EWS-FLI1
. PAX3-FKHR
. TLS-CHOP
. COL1A1-PDGFB

Correct Answer & Explanation

. SYT-SSX1

Explanation

The t(11;22) translocation is characteristic of Ewing sarcoma, resulting in the EWS-FLI1 fusion protein. SYT-SSX1 is seen in synovial sarcoma, PAX3-FKHR in alveolar rhabdomyosarcoma, TLS-CHOP in myxoid liposarcoma, and COL1A1-PDGFB in dermatofibrosarcoma protuberans.

Question 2569

Topic: 10. Pathology and Oncology

A 30-year-old woman presents with progressive knee pain. Radiographs reveal an eccentric, purely lytic epiphyseal lesion extending to the subchondral bone in the distal femur. A biopsy is performed, and the diagnosis of a Giant Cell Tumor (GCT) of bone is confirmed. Which of the following best describes the primary neoplastic cell population in this tumor?

. Multinucleated giant cells
. Mononuclear spindle cells
. Tissue macrophages
. Chondrocytes
. Atypical osteoblasts

Correct Answer & Explanation

. Multinucleated giant cells

Explanation

In a Giant Cell Tumor of bone, the actual neoplastic cells are the mononuclear spindle cells (stromal cells) of osteoblastic lineage. These neoplastic cells overexpress RANKL, which recruits and stimulates circulating monocyte-macrophage precursors to fuse and form the reactive, non-neoplastic multinucleated giant cells that are responsible for the aggressive bone resorption characteristic of the lesion.

Question 2570

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with thigh pain and a low-grade fever. Radiographs show a permeative lytic lesion in the diaphysis of the femur with an 'onion-skin' periosteal reaction. A biopsy confirms Ewing sarcoma. Which of the following chromosomal translocations is most commonly associated with this diagnosis?

. 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 classic t(11;22)(q24;q12) translocation is identified in approximately 85% of Ewing sarcomas. This translocation results in the fusion of the EWSR1 gene on chromosome 22 with the FLI1 gene on chromosome 11, creating a fusion protein that acts as an aberrant transcription factor. t(X;18) is seen in synovial sarcoma; t(12;16) is seen in myxoid liposarcoma; t(2;13) is seen in alveolar rhabdomyosarcoma; and t(9;22) is associated with extraskeletal myxoid chondrosarcoma.

Question 2571

Topic: 10. Pathology and Oncology

A 16-year-old girl is treated for a high-grade, intramedullary conventional osteosarcoma of the distal femur. After undergoing a standard regimen of neoadjuvant chemotherapy, she undergoes a wide surgical resection of the tumor. Which of the following parameters determined from the resected specimen is the most important independent prognostic indicator for her long-term survival?

. Maximal tumor diameter
. Predominant histologic subtype (e.g., osteoblastic vs. chondroblastic)
. Proximity to the articular surface
. Percentage of tumor necrosis
. Number of mitotic figures per high-power field

Correct Answer & Explanation

. Maximal tumor diameter

Explanation

The degree of tumor necrosis following neoadjuvant chemotherapy (evaluated histologically on the definitive surgical resection specimen) is widely considered the most significant prognostic factor for survival in osteosarcoma. A good histologic response, typically defined as greater than 90% tumor necrosis, is strongly correlated with improved disease-free and overall survival.

Question 2572

Topic: Bone Tumors

A 20-year-old college student complains of deep, aching anterior thigh pain that is notably worse at night. The pain is consistently and completely relieved within 30 minutes of taking ibuprofen.

A radiograph and subsequent CT scan reveal a 0.8 cm radiolucent nidus surrounded by dense reactive sclerosis in the femoral diaphysis. What is the most widely accepted definitive, minimally invasive treatment for this condition if medical management is intolerable?

. Intralesional curettage and bone grafting
. Wide en bloc resection
. Radiofrequency ablation (RFA)
. External beam radiation therapy
. Neoadjuvant chemotherapy followed by marginal excision

Correct Answer & Explanation

. Intralesional curettage and bone grafting

Explanation

The clinical presentation (nocturnal pain relieved by NSAIDs) and imaging findings (small radiolucent nidus <1.5 cm with surrounding sclerosis) are classic for an osteoid osteoma. Prostaglandin E2 levels are highly elevated in the nidus. If non-operative management (NSAIDs) fails or the patient desires definitive treatment, percutaneous Radiofrequency Ablation (RFA) under CT guidance is the standard of care with excellent success rates and minimal morbidity.

Question 2573

Topic: 10. Pathology and Oncology

A 45-year-old man presents with an increasingly painful shoulder over the past 6 months. Radiographs demonstrate a lytic lesion with rings and arcs of calcification in the proximal humerus, exhibiting endosteal scalloping that exceeds two-thirds of the cortical thickness. Biopsy reveals hypercellular hyaline cartilage with distinct permeation into the surrounding marrow spaces. What is the most appropriate management for this patient?

. Curettage, burring, and bone grafting
. Wide surgical excision
. Neoadjuvant chemotherapy followed by wide excision
. Radiation therapy
. Intralesional injection of corticosteroids

Correct Answer & Explanation

. Curettage, burring, and bone grafting

Explanation

The clinical presentation, radiographic findings (endosteal scalloping > 2/3 cortical thickness), and histologic hallmark of permeation into surrounding bone marrow spaces are diagnostic of a conventional chondrosarcoma. Unlike enchondromas, which can be observed or treated with curettage if symptomatic, conventional chondrosarcoma (even low-grade) typically requires surgical resection. Grade 1 lesions in the appendicular skeleton can sometimes be managed with aggressive extended intralesional curettage depending on exact location, but permeation often indicates at least a grade 1 or 2 lesion where wide surgical excision is the standard of care. Chondrosarcomas are notably chemo-resistant and radio-resistant.

Question 2574

Topic: 10. Pathology and Oncology

A 14-year-old girl presents with a rapidly expanding, painful mass in her distal femur. MRI reveals an expansile, multiloculated lytic lesion with prominent fluid-fluid levels. A biopsy confirms blood-filled spaces lacking a true endothelial lining, with giant cells present in the fibrous septa. What genetic translocation is most specific and diagnostic for the primary form of this neoplastic lesion?

. t(11;22) EWSR1-FLI1
. t(X;18) SYT-SSX
. t(16;17) CDH11-USP6
. t(2;13) PAX3-FOXO1
. t(12;16) FUS-DDIT3

Correct Answer & Explanation

. t(11;22) EWSR1-FLI1

Explanation

The lesion described is an aneurysmal bone cyst (ABC). While historically considered purely reactive, it is now known that primary ABCs are true neoplasms characterized by translocations involving the USP6 gene on chromosome 17. The most common translocation is t(16;17)(q22;p13), creating a CDH11-USP6 fusion gene. EWSR1-FLI1 is characteristic of Ewing sarcoma; SYT-SSX is found in synovial sarcoma; PAX3-FOXO1 in alveolar rhabdomyosarcoma; and FUS-DDIT3 in myxoid liposarcoma.

Question 2575

Topic: 10. Pathology and Oncology

A 16-year-old boy has recently completed a standard course of neoadjuvant chemotherapy for a conventional high-grade osteosarcoma of the distal femur, followed by wide surgical resection. Pathological examination of the resected tumor specimen reveals 95% tumor necrosis. Which of the following statements is true regarding this specific finding?

. It has no bearing on overall or event-free survival.
. It is considered a poor response, requiring immediate alternative post-operative chemotherapy.
. It dictates the immediate need for adjuvant radiotherapy to the tumor bed.
. It correlates with a significantly improved event-free and overall survival.
. It indicates that adjuvant postoperative chemotherapy can be safely omitted.

Correct Answer & Explanation

. It has no bearing on overall or event-free survival.

Explanation

The degree of tumor necrosis following neoadjuvant chemotherapy is one of the most important prognostic factors for conventional osteosarcoma. A histologic response of 90% or greater tumor necrosis (Huvos grade III or IV) is considered a 'good' response and correlates strongly with improved event-free and overall survival. Despite a good response, patients must still complete the full post-operative (adjuvant) course of chemotherapy; it cannot be omitted. Osteosarcoma is generally radio-resistant, so radiotherapy is not routinely used for local control unless margins are positive or the tumor is unresectable.

Question 2576

Topic: 10. Pathology and Oncology

A 12-year-old boy presents with intermittent low-grade fevers, mild weight loss, and a painful, swollen mid-thigh. Radiographs demonstrate a permeative, ill-defined destructive lesion in the femoral diaphysis with an 'onion-skin' periosteal reaction. Biopsy reveals sheets of uniform, small, round, blue cells. Which immunohistochemical marker is most consistently and strongly positive in this tumor?

. CD99 (MIC2)
. MyoD1
. Cytokeratin
. S-100
. LCA (CD45)

Correct Answer & Explanation

. CD99 (MIC2)

Explanation

The clinical and radiographic presentation, along with the small round blue cell histology, is highly characteristic of Ewing sarcoma. Ewing sarcoma cells demonstrate strong, diffuse, membranous staining for CD99 (the product of the MIC2 gene). MyoD1 is a marker for rhabdomyosarcoma; Cytokeratin is positive in epithelial tumors (carcinomas) and synovial sarcoma; S-100 is positive in neural crest tumors (e.g., melanoma, schwannoma) and chondroid tumors; LCA (CD45) is positive in lymphomas.

Question 2577

Topic: Bone Tumors

A 14-year-old boy presents with multiple painless, hard bony protuberances around his knees, ankles, and shoulders that have been present since early childhood. Radiographs demonstrate multiple pedunculated and sessile bone lesions pointing away from the joints, showing continuity of the cortex and medullary cavity with the host bone. Mutations in which of the following genes are most commonly responsible for this condition, and what is their normal cellular function?

. GNAS; encoding a G-protein alpha subunit
. FGFR3; encoding a tyrosine kinase receptor
. COMP; encoding a cartilage oligomeric matrix protein
. EXT1 and EXT2; encoding glycosyltransferases involved in heparan sulfate synthesis
. RUNX2; encoding a transcription factor for osteoblast differentiation

Correct Answer & Explanation

. GNAS; encoding a G-protein alpha subunit

Explanation

The patient has Multiple Hereditary Exostoses (MHE), also known as multiple osteochondromatosis. This autosomal dominant condition is 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 regulation of Indian hedgehog (Ihh) signaling at the growth plate, leading to the formation of osteochondromas. GNAS mutations cause McCune-Albright syndrome/fibrous dysplasia; FGFR3 mutations cause achondroplasia; COMP mutations cause multiple epiphyseal dysplasia / pseudoachondroplasia; RUNX2 mutations cause cleidocranial dysplasia.

Question 2578

Topic: Bone Tumors

A 25-year-old woman presents with hip pain and an impending pathological fracture of the proximal femur. Radiographs reveal a classic 'shepherd's crook' deformity with a diaphyseal 'ground-glass' appearance. The patient's medical history includes precocious puberty and hyperthyroidism. Which of the following best describes the underlying cellular pathophysiology of her musculoskeletal and endocrine abnormalities?

. A post-zygotic activating mutation in the GNAS gene causing increased intracellular cAMP
. A germline loss-of-function mutation in the EXT1 gene causing decreased heparan sulfate
. A defect in type I collagen synthesis (COL1A1) causing brittle bone matrix
. A missense mutation in the FGFR3 gene causing abnormal chondrocyte proliferation
. An activating mutation in the BRAF oncogene driving uncontrolled cell division

Correct Answer & Explanation

. A post-zygotic activating mutation in the GNAS gene causing increased intracellular cAMP

Explanation

The clinical picture describes McCune-Albright syndrome, a triad of polyostotic fibrous dysplasia, cafe-au-lait macules, and autonomous endocrine hyperfunction (such as precocious puberty). This condition is caused by a post-zygotic, somatic activating mutation in the GNAS gene, which encodes the alpha subunit of the Gs stimulating protein. This leads to constitutive activation of adenylate cyclase and uninhibited production of intracellular cyclic AMP (cAMP), driving the abnormal proliferation and differentiation in bone (fibrous dysplasia) and endocrine tissues.

Question 2579

Topic: 10. Pathology and Oncology

A 28-year-old man presents with a slow-growing, deep, painful mass in his popliteal fossa. MRI shows a well-circumscribed soft tissue mass adjacent to the knee joint but not originating from the joint space itself. Core needle biopsy reveals a biphasic tumor consisting of both spindle cells and epithelial-like gland formations. Which cytogenetic abnormality is diagnostic for this tumor?

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

Correct Answer & Explanation

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

Explanation

The clinical and histopathological findings (biphasic spindle and epithelial cells near a joint) describe Synovial Sarcoma. Despite its name, it does not arise from synovium. The pathognomonic chromosomal translocation for synovial sarcoma is t(X;18)(p11;q11), which fuses the SYT gene on chromosome 18 with one of the SSX genes (SSX1, SSX2, or SSX4) on the X chromosome. t(11;22) is Ewing sarcoma; t(12;16) is myxoid liposarcoma; t(2;13) is alveolar rhabdomyosarcoma; and t(9;22) is extraskeletal myxoid chondrosarcoma (or CML via Philadelphia chromosome).

Question 2580

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with progressive night pain in his proximal tibia that is reliably relieved by oral ibuprofen. Radiographs demonstrate a 1-cm radiolucent nidus surrounded by dense reactive sclerosis. What is the primary mechanism by which the nonsteroidal anti-inflammatory drug (NSAID) relieves his symptoms in this specific condition?

. Inhibition of local leukotriene synthesis
. Downregulation of substance P receptors
. Decreased production of prostaglandin E2 (PGE2)
. Direct suppression of osteoclastic bone resorption
. Inhibition of matrix metalloproteinases

Correct Answer & Explanation

. Inhibition of local leukotriene synthesis

Explanation

Osteoid osteoma is a benign bone-forming tumor characterized by a small radiolucent nidus surrounded by reactive sclerosis. The nidus cells secrete high levels of prostaglandins, particularly PGE2, which mediate the characteristic severe, nocturnal pain. NSAIDs provide dramatic pain relief by inhibiting cyclooxygenase (COX), thereby decreasing PGE2 production.

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