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10. Pathology and Oncology MCQs

Practice Set 303 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 6041

Topic: 10. Pathology and Oncology

A 26-year-old man presents with progressive swelling and pain in his ring finger metacarpophalangeal joint without a history of trauma. Imaging reveals a lytic, expansile subchondral lesion without cystic components. Which of the following is the most likely diagnosis?

. Enchondroma
. Aneurysmal bone cyst
. Giant cell tumor
. Osteoid osteoma
. Chondroblastoma

Correct Answer & Explanation

. Giant cell tumor

Explanation

Correct Answer: CThe subchondral location and expansile, lytic nature of the lesion in a skeletally mature patient are highly characteristic of a giant cell tumor of bone. While enchondromas are the most common benign bone tumors of the hand, they are typically diaphyseal/metaphyseal and often have calcifications. Aneurysmal bone cysts would typically show fluid-fluid levels on MRI and are less likely to be strictly subchondral.

Question 6042

Topic: 10. Pathology and Oncology

A 15-year-old boy completes neoadjuvant chemotherapy for osteosarcoma of the distal femur and subsequently undergoes wide surgical resection. Pathologic analysis is pending. What represents the most important prognostic factor for his long-term survival?

. The exact anatomic dimension of the tumor in centimeters
. The percentage of tumor necrosis observed in the resected specimen
. The specific subtype of osteosarcoma (e.g., telangiectatic vs. conventional)
. The surgical margins being greater than 5 cm
. The presence of a soft tissue extension pre-chemotherapy

Correct Answer & Explanation

. The percentage of tumor necrosis observed in the resected specimen

Explanation

The histologic response to neoadjuvant chemotherapy, specifically the percentage of tumor necrosis, is the single most critical prognostic indicator in osteosarcoma. Greater than 90% tumor necrosis is considered a 'good response' and correlates with significantly better long-term survival.

Question 6043

Topic: 10. Pathology and Oncology

A 68-year-old man with a long-standing history of an enlarged skull and progressive bowing of his tibia presents with a rapidly enlarging, highly painful mass over his proximal tibia. Serum alkaline phosphatase is markedly elevated. What is the most likely diagnosis of this new mass?

. Metastatic prostate cancer
. Multiple myeloma
. Secondary osteosarcoma
. Giant cell tumor of bone
. Chondrosarcoma

Correct Answer & Explanation

. Secondary osteosarcoma

Explanation

Secondary osteosarcoma is a rare (approx. 1%) but highly lethal complication of Paget's disease of bone. It must be strongly suspected when a patient with known Paget's disease develops new, severe, localized pain or a rapidly enlarging mass.

Question 6044

Topic: Bone Tumors
A 12-year-old girl presents with a limp. Radiographs demonstrate an expansile, ground-glass lesion in the proximal femur with a shepherd's crook deformity. She is also noted to have precocious puberty and irregular café-au-lait spots. What is the underlying molecular defect?
. Mutation in the GNAS1 gene resulting in decreased intracellular cAMP
. Mutation in the GNAS1 gene resulting in continuously elevated intracellular cAMP
. Mutation in the EXT1 gene
. Mutation in the NF1 gene
. Mutation in the PTHrP receptor

Correct Answer & Explanation

. Mutation in the GNAS1 gene resulting in continuously elevated intracellular cAMP

Explanation

McCune-Albright syndrome (polyostotic fibrous dysplasia, endocrine abnormalities, and "Coast of Maine" café-au-lait spots) is caused by a post-zygotic activating mutation in the GNAS1 gene. This leads to constitutive activation of adenylate cyclase and elevated intracellular cAMP.

Question 6045

Topic: 10. Pathology and Oncology

A 65-year-old man with increasing hat size and unilateral hearing loss develops sudden, severe right thigh pain. Radiographs of the femur show a new, destructive lytic lesion with cortical breakthrough in an area of pre-existing thickened, coarsened trabeculae. What is the most common malignant transformation in this patient's underlying disease?

. Chondrosarcoma
. Ewing sarcoma
. Osteosarcoma
. Fibrosarcoma
. Multiple myeloma

Correct Answer & Explanation

. Osteosarcoma

Explanation

Paget's disease of bone carries approximately a 1% risk of malignant transformation. The most common secondary malignancy is osteosarcoma, which typically presents with sudden, severe pain and a destructive lesion in pagetic bone.

Question 6046

Topic: Bone Tumors
A 12-year-old girl is evaluated for precocious puberty and large café-au-lait spots with irregular, "coast of Maine" borders. Radiographs reveal polyostotic radiolucent bone lesions with a "ground-glass" matrix. What is the underlying genetic mutation?
. Activating mutation in GNAS1
. Loss of function in NF1
. Mutation in EXT1
. Mutation in SH3BP2
. Mutation in COMP

Correct Answer & Explanation

. Activating mutation in GNAS1

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, café-au-lait spots, and endocrine abnormalities (like precocious puberty). It is caused by a sporadic, post-zygotic activating mutation in the GNAS1 gene.

Question 6047

Topic: 10. Pathology and Oncology
A 2-year-old boy presents with anterolateral bowing of his left tibia. He has six café-au-lait spots with smooth borders on his trunk. Radiographs reveal a narrowed medullary canal and sclerosis at the apex of the bow. Which of the following is true regarding his underlying condition?
. The underlying defect is a gain of function in the NF1 gene
. It is inherited in an autosomal recessive pattern
. The affected gene normally downregulates the Ras signaling pathway
. Resection and bone grafting alone yield a 90% success rate
. The café-au-lait spots typically have irregular borders

Correct Answer & Explanation

. The affected gene normally downregulates the Ras signaling pathway

Explanation

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder caused by a loss-of-function mutation in the NF1 gene, which encodes neurofibromin. Neurofibromin normally acts as a tumor suppressor by downregulating the Ras signaling pathway.

Question 6048

Topic: 10. Pathology and Oncology

An infant is evaluated for failure to thrive, hepatosplenomegaly, and cranial nerve palsies. Radiographs show diffusely dense, bone-within-a-bone appearance in the spine. A mutation in which of the following enzymes is most commonly associated with the malignant autosomal recessive form of this disease?

. Tartrate-resistant acid phosphatase
. Cathepsin K
. Carbonic anhydrase II
. Tissue-nonspecific alkaline phosphatase
. Matrix metalloproteinase-9

Correct Answer & Explanation

. Carbonic anhydrase II

Explanation

Malignant infantile osteopetrosis is commonly caused by a mutation in Carbonic Anhydrase II. This results in a defective osteoclast ruffled border and an inability to create the acidic environment necessary for bone resorption.

Question 6049

Topic: 10. Pathology and Oncology

A 6-year-old child presents with a painful, firm mass on his back following minor trauma, and a short, malformed great toe. Over several weeks, the mass gradually turns into bone. Which of the following is the most appropriate management regarding the back mass?

. Immediate wide surgical excision of the mass
. Incisional biopsy to confirm the diagnosis
. Observation and avoidance of trauma or biopsy
. Intravenous bisphosphonate therapy
. Local radiation therapy

Correct Answer & Explanation

. Observation and avoidance of trauma or biopsy

Explanation

Fibrodysplasia ossificans progressiva (FOP) is caused by an ACVR1 gene mutation. Biopsy or surgical excision of the heterotopic ossification triggers explosive new bone formation and must be strictly avoided.

Question 6050

Topic: 10. Pathology and Oncology

A 72-year-old man with a long-standing history of polyostotic Paget disease suddenly develops severe, unrelenting pain and swelling in his right thigh. Radiographs show cortical destruction and a soft tissue mass. What is the most likely diagnosis?

. Multiple myeloma
. Chondrosarcoma
. Osteosarcoma
. Ewing sarcoma
. Metastatic prostate cancer

Correct Answer & Explanation

. Osteosarcoma

Explanation

Malignant transformation occurs in about 1% of patients with Paget disease. The most common secondary malignancy is osteosarcoma, which typically presents with new-onset, severe localized pain and an expansile lytic lesion.

Question 6051

Topic: Bone Tumors
A 12-year-old girl sustains a low-energy proximal femur fracture. Radiographs show a distinct "ground-glass" lytic lesion in the proximal femur with a shepherd's crook deformity. She has several large, irregular hyperpigmented macules on her back and a history of precocious puberty. The underlying mutation for this syndrome results in abnormal function of which of the following?
. Gi-protein coupled receptor
. Gs-alpha protein subunit
. Tyrosine kinase receptor
. Wnt/beta-catenin signaling pathway
. RANKL expression

Correct Answer & Explanation

. Gs-alpha protein subunit

Explanation

This is McCune-Albright syndrome, featuring polyostotic fibrous dysplasia, café-au-lait spots, and endocrinopathies. It is caused by an activating post-zygotic mutation in the GNAS1 gene, which encodes the Gs-alpha protein subunit, leading to excessive intracellular cAMP.

Question 6052

Topic: 10. Pathology and Oncology

A 55-year-old male presents with thigh pain. Radiographs show a permeative diaphyseal lesion with minimal periosteal reaction. Biopsy reveals sheets of small round blue cells expressing CD20 and CD45.

What is the most appropriate initial management?

. Wide surgical excision
. Neoadjuvant chemotherapy followed by wide resection
. Systemic chemotherapy and localized radiation therapy
. Intralesional curettage and bone grafting
. Above-knee amputation

Correct Answer & Explanation

. Systemic chemotherapy and localized radiation therapy

Explanation

Primary bone lymphoma typically presents as a permeative lesion in older adults and stains positive for CD45 (LCA) and CD20 (B-cell marker). Treatment is primarily medical, utilizing systemic chemotherapy (e.g., R-CHOP) combined with localized radiation therapy.

Question 6053

Topic: 10. Pathology and Oncology

A 22-year-old male presents with chronic knee pain. Radiographs show an eccentric, lytic, bubbly lesion with a sclerotic margin in the proximal tibial metaphysis.

Histology shows stellate cells in a myxoid background with multinucleated giant cells at the lobular periphery. What is the diagnosis?

. Chondroblastoma
. Chondromyxoid fibroma
. Aneurysmal bone cyst
. Non-ossifying fibroma
. Enchondroma

Correct Answer & Explanation

. Chondromyxoid fibroma

Explanation

Chondromyxoid fibroma is a rare benign cartilage tumor presenting as an eccentric metaphyseal lesion. Histologically, it features a lobular architecture with central myxoid tissue and peripheral hypercellularity with giant cells.

Question 6054

Topic: 10. Pathology and Oncology

A 60-year-old female presents with shoulder pain. MRI reveals a large soft tissue mass surrounding the proximal humerus with diffuse marrow signal changes, but remarkably intact cortical bone on T1-weighted images.

What is the most likely diagnosis?

. Osteosarcoma
. Ewing sarcoma
. Multiple myeloma
. Primary bone lymphoma
. Metastatic breast carcinoma

Correct Answer & Explanation

. Primary bone lymphoma

Explanation

A classic imaging hallmark of primary bone lymphoma is a massive soft tissue mass associated with extensive marrow involvement but with relatively preserved or intact cortical bone.

Question 6055

Topic: Bone Tumors

A 4-year-old boy presents with a painless, asymmetric, hard mass on the medial aspect of his right ankle. Radiographs show an irregular, lobulated, ossifying mass arising from the medial aspect of the distal tibial epiphysis. What is the most likely diagnosis?

. Multiple epiphyseal dysplasia
. Dysplasia epiphysealis hemimelica (Trevor disease)
. Osteochondroma
. Chondroblastoma
. Blount disease

Correct Answer & Explanation

. Dysplasia epiphysealis hemimelica (Trevor disease)

Explanation

Trevor disease (dysplasia epiphysealis hemimelica) involves asymmetrical cartilage overgrowth at the epiphysis, most commonly affecting the medial side of the knee or ankle in young children.

Question 6056

Topic: 10. Pathology and Oncology

A 28-year-old female undergoes a biopsy of a painful, eccentric, lytic lesion in the distal femur which confirms chondromyxoid fibroma.

Which of the following is the most appropriate definitive management?

. Observation with serial radiographs
. Intralesional curettage, high-speed burring, and bone grafting
. Wide surgical resection and endoprosthetic reconstruction
. Primary external beam radiation therapy
. Radiofrequency ablation

Correct Answer & Explanation

. Intralesional curettage, high-speed burring, and bone grafting

Explanation

Chondromyxoid fibroma is a locally aggressive benign tumor. The gold standard treatment is extended intralesional curettage using a high-speed burr, followed by bone grafting or cementation.

Question 6057

Topic: 10. Pathology and Oncology

A biopsy of a destructive diaphyseal lesion in the femur of a 16-year-old boy shows small round blue cells. Immunohistochemistry is strongly positive for CD45 and CD20, but negative for CD99 and FLI-1. What is the most appropriate systemic treatment for this condition?

. Vincristine, doxorubicin, and cyclophosphamide (VDC)
. Rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP)
. High-dose methotrexate and cisplatin
. Imatinib mesylate
. Denosumab

Correct Answer & Explanation

. Rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP)

Explanation

The immunohistochemistry profile (CD45+, CD20+, CD99-) indicates a primary diffuse large B-cell lymphoma of bone, not Ewing sarcoma. The standard systemic chemotherapy regimen is R-CHOP.

Question 6058

Topic: 10. Pathology and Oncology

A 19-year-old patient presents with pain in the proximal tibia. Imaging demonstrates a sharply demarcated, eccentric, radiolucent lesion in the metaphysis extending towards the diaphysis, without true epiphyseal involvement.

Histology reveals a lobular architecture with central myxoid tissue and hypercellular peripheries containing multinucleated giant cells. Which is the most likely diagnosis?

. Chondroblastoma
. Chondromyxoid fibroma
. Giant cell tumor of bone
. Osteoblastoma
. Clear cell chondrosarcoma

Correct Answer & Explanation

. Chondromyxoid fibroma

Explanation

The location (eccentric, metaphyseal) and histology (lobular pattern with myxoid centers and hypercellular peripheries with giant cells) are classic for Chondromyxoid Fibroma.

Question 6059

Topic: 10. Pathology and Oncology

A 45-year-old male presents with deep, aching thigh pain. Imaging shows a permeative lesion in the femoral diaphysis with a large soft tissue mass. Biopsy reveals sheets of atypical lymphoid cells. Which immunohistochemical marker is most likely positive in this primary bone tumor?

. CD99
. CD20
. S-100
. Cytokeratin
. SMA

Correct Answer & Explanation

. CD20

Explanation

Primary bone lymphoma is most commonly a Diffuse Large B-Cell Lymphoma (DLBCL). These tumor cells strongly express B-cell markers such as CD20 and CD79a, alongside CD45 (LCA). CD99 is typically associated with Ewing sarcoma, which presents in a younger demographic.

Question 6060

Topic: 10. Pathology and Oncology

A 55-year-old male presents with thigh pain. Radiographs show a permeative diaphyseal lesion with minimal cortical destruction. MRI reveals a massive soft tissue component. Biopsy confirms CD20+ atypical lymphoid cells. What is the most appropriate primary management?

. Neoadjuvant chemotherapy and wide resection
. Wide resection alone
. Intralesional curettage and bone grafting
. Multi-agent systemic chemotherapy and local radiation
. Amputation

Correct Answer & Explanation

. Multi-agent systemic chemotherapy and local radiation

Explanation

Primary lymphoma of bone typically presents with a large soft tissue mass despite relatively subtle destructive changes on radiographs. The mainstay of treatment is systemic multi-agent chemotherapy combined with local external beam radiation.

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