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10. Pathology and Oncology MCQs

Practice Set 304 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 6061

Topic: 10. Pathology and Oncology

A 20-year-old male presents with chronic knee pain. Radiographs demonstrate an eccentric, well-circumscribed, lytic lesion with a sclerotic margin in the proximal tibial metaphysis. Biopsy reveals lobules of spindle or stellate cells in a myxoid background separated by highly cellular fibrous bands containing osteoclast-like giant cells. What is the most likely diagnosis?

. Chondroblastoma
. Chondromyxoid fibroma
. Non-ossifying fibroma
. Giant cell tumor
. Aneurysmal bone cyst

Correct Answer & Explanation

. Chondromyxoid fibroma

Explanation

Chondromyxoid fibroma typically presents as an eccentric, lytic metaphyseal lesion. The classic histologic appearance consists of lobules of myxoid and chondroid tissue separated by fibrous septa containing multinucleated giant cells.

Question 6062

Topic: 10. Pathology and Oncology

A 45-year-old woman is evaluated for a destructive diaphyseal lesion in the humerus. Histology reveals a diffuse infiltrate of small to medium-sized round blue cells. Immunohistochemistry is positive for CD45 (LCA) and CD20, but negative for CD99 and cytokeratin. Which diagnosis is confirmed?

. Ewing sarcoma
. Multiple myeloma
. Diffuse large B-cell lymphoma of bone
. Metastatic carcinoma
. Osteosarcoma

Correct Answer & Explanation

. Diffuse large B-cell lymphoma of bone

Explanation

Primary lymphoma of bone is a round blue cell tumor that stains positive for CD45 (Leukocyte Common Antigen) and B-cell markers like CD20. It is negative for CD99 (Ewing sarcoma) and cytokeratin (metastatic carcinoma).

Question 6063

Topic: Bone Tumors

A 4-year-old boy presents with a painless, asymmetric swelling on the medial aspect of his ankle. Radiographs show an irregular, ossified mass arising from the medial epiphysis of the distal tibia. Histologically, the lesion strongly resembles an osteochondroma. What is the most likely diagnosis?

. Multiple hereditary exostoses
. Chondrodysplasia punctata
. Dysplasia epiphysealis hemimelica (Trevor disease)
. Ollier disease
. Spondyloepiphyseal dysplasia

Correct Answer & Explanation

. Dysplasia epiphysealis hemimelica (Trevor disease)

Explanation

Dysplasia epiphysealis hemimelica (Trevor disease) is characterized by an osteochondroma-like outgrowth arising from the epiphysis, most commonly on the medial side of the knee or ankle. It results in asymmetric epiphyseal enlargement and joint deformity.

Question 6064

Topic: Bone Tumors

A 48-year-old male presents with severe right thigh pain. Plain radiographs appear largely unremarkable except for a very subtle permeative radiolucency in the diaphysis. MRI demonstrates extensive marrow replacement and a massive soft tissue mass surrounding the bone. Which of the following is the most likely diagnosis?

. Osteoid osteoma
. Primary lymphoma of bone
. Chondrosarcoma
. Parosteal osteosarcoma
. Fibrous dysplasia

Correct Answer & Explanation

. Primary lymphoma of bone

Explanation

The combination of minimal cortical destruction on plain radiographs with an extensive soft tissue mass on MRI is a hallmark presentation of primary lymphoma of bone. The tumor permeates through the Haversian canals without completely destroying the cortex.

Question 6065

Topic: Bone Tumors

A 6-year-old girl is noted to have early breast development and vaginal bleeding. She complains of left hip pain, and radiographs reveal a ground-glass, expansile lytic lesion in the proximal femur with a "shepherd's crook" deformity. Physical exam reveals large, irregular hyperpigmented skin macules. A mutation in which of the following genes is responsible for this condition?

. EXT1
. FGFR3
. GNAS1
. PTPN11
. COL1A1

Correct Answer & Explanation

. GNAS1

Explanation

This patient has McCune-Albright syndrome, characterized by polyostotic fibrous dysplasia, precocious puberty, and cafe-au-lait spots. It is caused by an activating post-zygotic mutation in the GNAS1 gene, resulting in persistent adenylyl cyclase activity.

Question 6066

Topic: 10. Pathology and Oncology

A 22-year-old male presents with persistent left knee pain. Radiographs reveal an eccentric, purely lytic lesion in the proximal tibial metaphysis with a distinct sclerotic inner margin.

A biopsy demonstrates lobules of myxoid and chondroid tissue with hypercellular peripheries. What is the most likely diagnosis?

. Chondroblastoma
. Chondrosarcoma
. Chondromyxoid fibroma
. Aneurysmal bone cyst
. Giant cell tumor of bone

Correct Answer & Explanation

. Chondromyxoid fibroma

Explanation

Chondromyxoid fibroma (CMF) is a rare, benign cartilage tumor that classically presents as an eccentric metaphyseal radiolucency with a sclerotic inner margin. Histologically, it features biphasic lobules with hypocellular centers and hypercellular peripheries containing stellate cells.

Question 6067

Topic: 10. Pathology and Oncology

A 55-year-old male presents with thigh pain. Radiographs show a large permeative, 'moth-eaten' lesion in the femoral diaphysis with minimal cortical expansion.

Biopsy confirms primary diffuse large B-cell lymphoma of bone. What is the standard definitive treatment?

. Wide surgical resection and endoprosthetic reconstruction
. Systemic chemotherapy and localized radiotherapy
. Intralesional curettage and bone grafting
. Amputation proximal to the lesion
. Observation with serial radiographs

Correct Answer & Explanation

. Systemic chemotherapy and localized radiotherapy

Explanation

Primary bone lymphoma is highly responsive to non-operative treatment. The standard of care is systemic multidrug chemotherapy (e.g., CHOP-R) combined with localized external beam radiotherapy, reserving surgery strictly for impending or actual pathologic fractures.

Question 6068

Topic: Bone Tumors

Which histologic feature is considered the hallmark of a chondromyxoid fibroma, aiding in differentiating it from chondrosarcoma?

. Abundant delicate 'chicken-wire' calcifications
. Lobular architecture with hypercellular margins and hypocellular centers
. Diffuse permeation of host bone trabeculae
. Sheets of uniform small round blue cells
. Presence of anaplastic chondrocytes with atypical mitoses

Correct Answer & Explanation

. Lobular architecture with hypercellular margins and hypocellular centers

Explanation

Chondromyxoid fibroma exhibits a distinct pseudo-lobular pattern with central hypocellular myxoid tissue and hypercellular peripheries containing multinucleated giant cells. Chondrosarcomas typically lack this organized lobular zonation and show permeation of native bone.

Question 6069

Topic: 10. Pathology and Oncology

A classic imaging characteristic that strongly suggests primary bone lymphoma over other aggressive sarcomas (such as Ewing sarcoma or osteosarcoma) is:

. A large soft-tissue mass with relatively preserved cortical bone contour
. Extensive sunburst periosteal reaction
. Dense, cloud-like matrix mineralization within the medullary canal
. A purely epiphyseal geographic lytic lesion
. A fluid-fluid level on MRI without solid components

Correct Answer & Explanation

. A large soft-tissue mass with relatively preserved cortical bone contour

Explanation

Primary bone lymphoma often presents with a massive soft-tissue component that seems disproportionately large compared to the relatively preserved cortical bone structure. The tumor typically spreads through Haversian canals without completely destroying the cortex.

Question 6070

Topic: 10. Pathology and Oncology

What is the recommended surgical management for a symptomatic chondromyxoid fibroma in the proximal tibia of a 25-year-old patient?

. Core needle biopsy followed by observation
. Extended intralesional curettage with high-speed burring and bone grafting
. Wide en bloc resection and endoprosthetic replacement
. Intramedullary nailing
. Pre-operative radiation followed by marginal excision

Correct Answer & Explanation

. Extended intralesional curettage with high-speed burring and bone grafting

Explanation

Chondromyxoid fibroma is a benign but locally aggressive tumor. The standard of care is extended intralesional curettage utilizing a high-speed burr (with or without local adjuvants) followed by bone grafting or cementation.

Question 6071

Topic: 10. Pathology and Oncology

During the immunohistochemical evaluation of a suspected primary bone lymphoma biopsy, which of the following surface markers is most likely to be strongly positive?

. CD99
. CD20
. S-100
. Cytokeratin
. Vimentin

Correct Answer & Explanation

. CD20

Explanation

The vast majority of primary bone lymphomas are diffuse large B-cell lymphomas. Therefore, they will strongly express B-cell markers such as CD20, along with the leukocyte common antigen CD45.

Question 6072

Topic: 10. Pathology and Oncology

A 55-year-old man presents with dull, aching thigh pain for 3 months. Radiographs demonstrate a permeative, moth-eaten radiolucent lesion in the femoral diaphysis with minimal periosteal reaction.

Biopsy reveals sheets of uniform, small round blue cells. Immunohistochemistry is positive for CD20 and CD45. What is the standard initial treatment?

. Wide surgical resection and endoprosthetic reconstruction
. Preoperative radiation followed by wide resection
. Systemic chemotherapy and localized radiation therapy
. Intralesional curettage, adjuvant phenol, and cementation
. Amputation

Correct Answer & Explanation

. Systemic chemotherapy and localized radiation therapy

Explanation

The diagnosis is primary bone lymphoma (diffuse large B-cell lymphoma), supported by the permeative lesion, age, and CD20/CD45 positivity. The primary treatment is multi-agent chemotherapy (e.g., R-CHOP) combined with localized radiation; surgery is reserved for impending or actual pathologic fractures.

Question 6073

Topic: 10. Pathology and Oncology

A 60-year-old male presents with deep thigh pain.

Biopsy reveals sheets of uniform, small to medium-sized cells with prominent nucleoli. The cells are positive for CD45 and CD20. Which of the following immunohistochemical markers is also most likely to be positive, confirming the diagnosis?

. CD99
. PAX5
. S-100
. Cytokeratin
. MyoD1

Correct Answer & Explanation

. PAX5

Explanation

Primary bone lymphoma is most commonly a diffuse large B-cell lymphoma (DLBCL). These tumors typically express B-cell markers such as CD20, CD45 (LCA), and PAX5, distinguishing them from other small round blue cell tumors.

Question 6074

Topic: Bone Tumors

A 45-year-old male completes definitive radiation therapy for primary diffuse large B-cell lymphoma of the femoral diaphysis. Which of the following is the most significant orthopedic complication directly associated with treating appendicular primary bone lymphoma exclusively with local high-dose radiation?

. Secondary osteosarcoma within 1 year
. Avascular necrosis of the femoral head
. Pathologic fracture
. Chronic osteomyelitis
. Rapid systemic metastasis

Correct Answer & Explanation

. Pathologic fracture

Explanation

Radiation therapy alone for primary bone lymphoma in weight-bearing bones carries a high risk of subsequent pathologic fracture due to radiation-induced osteonecrosis and delayed bone remodeling. This has shifted modern paradigms toward combined chemoradiation or prophylactic stabilization.

Question 6075

Topic: 10. Pathology and Oncology

A 22-year-old female undergoes a core needle biopsy of an eccentric, lytic metaphyseal lesion in the distal femur. The pathology report confirms chondromyxoid fibroma. What is the most appropriate surgical treatment to minimize recurrence?

. Intralesional curettage alone
. Extended curettage with high-speed burring and filling with bone graft or cement
. Wide en bloc resection and endoprosthetic reconstruction
. Preoperative chemotherapy followed by wide resection
. Radiofrequency ablation

Correct Answer & Explanation

. Extended curettage with high-speed burring and filling with bone graft or cement

Explanation

Chondromyxoid fibroma is a benign but locally aggressive tumor with a high recurrence rate if treated with simple curettage. Extended intralesional curettage with high-speed burring and adjuvant treatment (e.g., phenol, cement) is the gold standard.

Question 6076

Topic: 10. Pathology and Oncology

A 28-year-old male presents with a permeative lytic lesion of the humerus. A biopsy yields a small round blue cell tumor. The pathologist performs a reticulin stain to help differentiate between primary bone lymphoma and Ewing sarcoma. What is the classic reticulin staining pattern for primary bone lymphoma?

. Reticulin fibers encircle large nests or lobules of cells
. Reticulin fibers individually surround each tumor cell
. Complete absence of reticulin fibers
. Reticulin fibers organized in a parallel herringbone pattern
. Reticulin fibers exclusively located perivascularly

Correct Answer & Explanation

. Reticulin fibers individually surround each tumor cell

Explanation

In primary bone lymphoma, reticulin staining typically highlights a dense network of fibers surrounding individual tumor cells. In contrast, Ewing sarcoma shows reticulin fibers surrounding groups or nests of cells rather than individual cells.

Question 6077

Topic: 10. Pathology and Oncology

A 60-year-old man presents with dull thigh pain. Plain radiographs show a subtle permeative osteolytic lesion in the femoral diaphysis with minimal periosteal reaction. MRI reveals extensive marrow replacement extending far beyond the radiographic abnormalities.

Histological evaluation of a core biopsy will most likely reveal cells that strongly express which of the following markers?

. Cytokeratin
. CD99
. CD20
. S-100
. Smooth muscle actin

Correct Answer & Explanation

. CD20

Explanation

The clinical and imaging findings are highly characteristic of primary bone lymphoma, often appearing as a 'ghost tumor' with extensive MRI marrow involvement. Primary bone lymphoma is typically a diffuse large B-cell lymphoma, which strongly expresses the B-cell marker CD20.

Question 6078

Topic: 10. Pathology and Oncology

A 22-year-old presents with chronic proximal tibial pain. Radiographs demonstrate a well-defined, eccentric, lucent metaphyseal lesion with a sclerotic rim.

Biopsy shows lobules of myxoid tissue separated by fibrous septa containing giant cells. What is the recommended treatment?

. Observation with serial radiographs
. Neoadjuvant chemotherapy and wide resection
. Intralesional curettage with high-speed burr and bone grafting
. Radiofrequency ablation
. En bloc resection and endoprosthetic reconstruction

Correct Answer & Explanation

. Intralesional curettage with high-speed burr and bone grafting

Explanation

The diagnosis is a chondromyxoid fibroma (CMF), a rare benign cartilage tumor. The standard treatment is intralesional extended curettage (using a high-speed burr) followed by bone grafting or cementation to minimize the risk of local recurrence.

Question 6079

Topic: 10. Pathology and Oncology

A 45-year-old male is diagnosed with primary diffuse large B-cell lymphoma of the humerus based on an image-guided core needle biopsy. The cortical continuity is preserved, and the calculated Mirels score is 6. What is the most appropriate initial management?

. Prophylactic intramedullary nailing followed by radiation
. Wide surgical resection and endoprosthetic reconstruction
. Multi-agent chemotherapy combined with Rituximab
. Isolated localized external beam radiation therapy
. Neoadjuvant radiation followed by en bloc resection

Correct Answer & Explanation

. Multi-agent chemotherapy combined with Rituximab

Explanation

The primary treatment for primary bone lymphoma (diffuse large B-cell) is multi-agent chemotherapy (such as R-CHOP) with or without consolidative radiation. Surgery is strictly reserved for actual or impending fractures, which are unlikely with a Mirels score of 6.

Question 6080

Topic: 10. Pathology and Oncology

A 50-year-old woman complains of persistent knee pain. Plain radiographs show only subtle, ill-defined diaphyseal permeation. MRI reveals uniform low T1 signal replacing the entire distal femoral marrow cavity.

Which core needle biopsy finding would definitively confirm the most likely diagnosis?

. CD45 and CD20 positive sheets of small round blue cells
. CD99 positive small round blue cells with a t(11;22) translocation
. Atypical spindle cells producing delicate, lace-like osteoid
. S-100 positive binucleated cells in a cartilaginous lacunar background
. CD1a positive histiocytic cells with prominent eosinophils

Correct Answer & Explanation

. CD45 and CD20 positive sheets of small round blue cells

Explanation

The striking mismatch between minimal plain radiograph findings and extensive MRI marrow replacement is a hallmark of primary bone lymphoma ('ghost tumor'). Biopsy will yield small round blue cells strongly positive for leukocyte common antigen (CD45) and B-cell markers (CD20).

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