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10. Pathology and Oncology MCQs

Practice Set 318 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 6341

Topic: 10. Pathology and Oncology

A 14-year-old male presents with neck pain and a lytic lesion expanding the C4 lamina and pedicle. A needle biopsy confirms an aneurysmal bone cyst. What is the most appropriate next step in management prior to surgical resection?

. Radiation therapy
. Preoperative selective arterial embolization
. Observation and bracing
. Systemic chemotherapy
. Radiofrequency ablation

Correct Answer & Explanation

. Preoperative selective arterial embolization

Explanation

Spinal aneurysmal bone cysts are highly vascular and typically involve the posterior elements. Preoperative selective arterial embolization is recommended to significantly reduce intraoperative blood loss before excision.

Question 6342

Topic: 10. Pathology and Oncology

A 40-year-old female with known polyostotic fibrous dysplasia presents with a newly noticed, painless soft tissue mass in her thigh. Biopsy demonstrates a hypocellular lesion with stellate cells embedded in an abundant myxoid stroma. What is the diagnosis?

. Lipoma
. Mazabraud syndrome
. Schwannoma
. Hemangioma
. Soft tissue sarcoma

Correct Answer & Explanation

. Mazabraud syndrome

Explanation

Mazabraud syndrome is the rare association of fibrous dysplasia with single or multiple intramuscular myxomas. These soft tissue masses are typically benign and asymptomatic, though they can cause local mechanical symptoms.

Question 6343

Topic: Bone Tumors

What is considered the gold standard surgical treatment to minimize recurrence for an aggressive aneurysmal bone cyst of the proximal tibia in a 16-year-old?

. En bloc wide resection
. Intralesional curettage alone
. Extended curettage with high-speed burring and adjuvant therapy
. Primary sclerotherapy
. Amputation

Correct Answer & Explanation

. Extended curettage with high-speed burring and adjuvant therapy

Explanation

Extended curettage with a high-speed burr and the use of chemical or physical adjuvants (e.g., phenol, argon beam, cryotherapy) is the gold standard for ABCs. This aggressive local treatment significantly lowers the recurrence rate compared to simple curettage.

Question 6344

Topic: Bone Tumors

Which of the following is the histological hallmark of fibrous dysplasia?

. Endothelial-lined blood spaces separated by fibrous septa
. Chondroid matrix with a "chicken wire" calcification pattern
. Irregular trabeculae of woven bone lacking osteoblastic rimming in a fibrous stroma
. Sheets of small round blue cells with scant cytoplasm
. Abundant multinucleated giant cells in a sea of mononuclear cells

Correct Answer & Explanation

. Irregular trabeculae of woven bone lacking osteoblastic rimming in a fibrous stroma

Explanation

The classic histological finding of fibrous dysplasia is irregular, C- or W-shaped trabeculae of woven bone ("Chinese characters") arising directly from a fibrous stroma. Crucially, these bone trabeculae lack functional osteoblastic rimming.

Question 6345

Topic: Bone Tumors

Which endocrinopathy is the most common and classic manifestation associated with McCune-Albright syndrome?

. Hypothyroidism
. Central diabetes insipidus
. Precocious puberty
. Primary adrenal insufficiency
. Hyperparathyroidism

Correct Answer & Explanation

. Precocious puberty

Explanation

Peripheral precocious puberty is the most common endocrine abnormality in McCune-Albright syndrome, particularly in females. It results from autonomous, gonadotropin-independent ovarian estrogen production driven by the GNAS mutation.

Question 6346

Topic: Bone Tumors

Which of the following radiographic features best differentiates an aneurysmal bone cyst (ABC) from a unicameral bone cyst (UBC) in a long bone?

. An ABC is typically centrally located within the medullary canal.
. An ABC is typically eccentric and expansile, often blowing out the cortex.
. A UBC frequently crosses the open physis into the epiphysis.
. A UBC demonstrates diagnostic fluid-fluid levels on MRI.
. An ABC consistently resolves spontaneously with skeletal maturity.

Correct Answer & Explanation

. An ABC is typically eccentric and expansile, often blowing out the cortex.

Explanation

Radiographically, an ABC is an eccentric, expansile, lytic lesion that may thin or "blow out" the cortex. In contrast, a UBC is typically centrally located within the metaphysis or diaphysis and rarely expands beyond the normal width of the physis.

Question 6347

Topic: Bone Tumors

A 12-year-old boy presents with knee pain and swelling. Radiographs show an eccentric, expansile lytic lesion in the distal femoral metaphysis. MRI demonstrates multiple fluid-fluid levels. Genetic analysis of the tissue is most likely to reveal which of the following translocations?

. t(11;22)
. t(X;18)
. t(12;16)
. t(16;17)
. t(2;13)

Correct Answer & Explanation

. t(16;17)

Explanation

The diagnosis is an aneurysmal bone cyst (ABC). Primary ABCs are neoplasms driven by a specific t(16;17) translocation that upregulates the USP6 gene.

Question 6348

Topic: Bone Tumors

A 25-year-old female presents with a progressive bowing deformity of her proximal femur. Radiographs display a "ground-glass" appearance in the medullary canal with a "Shepherd's crook" deformity. A mutation in which of the following genes is responsible for this condition?

. EXT1
. GNAS
. FGFR3
. COL1A1
. RUNX2

Correct Answer & Explanation

. GNAS

Explanation

The patient has fibrous dysplasia, caused by a post-zygotic, activating missense mutation in the GNAS gene. This leads to constitutive activation of the Gs-alpha protein and increased intracellular cAMP, disrupting normal osteoblast differentiation.

Question 6349

Topic: 10. Pathology and Oncology

Histological evaluation of a rapidly growing, expansile bone lesion in a 15-year-old boy reveals cavernous, blood-filled spaces separated by fibrous septae containing fibroblasts, multinucleated giant cells, and reactive woven bone. Which of the following is a definitive characteristic of the vascular spaces in this lesion?

. They are lined by a single layer of atypical endothelial cells
. They lack a true endothelial lining
. They contain prominent smooth muscle in their walls
. They show uniform expression of CD31 and CD34
. They are characterized by numerous intraluminal thrombi

Correct Answer & Explanation

. They lack a true endothelial lining

Explanation

Aneurysmal bone cysts are characterized by blood-filled cystic spaces that are NOT true blood vessels. Therefore, they lack a true endothelial lining, differentiating them from vascular tumors like hemangiomas or angiosarcomas.

Question 6350

Topic: Bone Tumors
A 9-year-old girl is diagnosed with polyostotic fibrous dysplasia. Physical examination reveals a large hyperpigmented macule on her back with irregular borders. Which of the following endocrine abnormalities is most commonly associated with her underlying syndrome?
. Hyperthyroidism
. Acromegaly
. Precocious puberty
. Cushing syndrome
. Hyperparathyroidism

Correct Answer & Explanation

. Precocious puberty

Explanation

The patient has McCune-Albright syndrome (polyostotic fibrous dysplasia, "coast of Maine" café-au-lait spots, and endocrinopathies). Precocious puberty is the most common endocrine manifestation of this syndrome.

Question 6351

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with back pain and mild lower extremity weakness. Imaging reveals an expansile, multiloculated lytic lesion in the posterior elements of the L3 vertebra with epidural extension. Biopsy confirms an aneurysmal bone cyst. What is the most appropriate next step in management to minimize surgical morbidity?

. Immediate en bloc resection
. Preoperative selective arterial embolization followed by intralesional curettage
. High-dose radiation therapy
. Systemic chemotherapy
. Observation and bracing

Correct Answer & Explanation

. Preoperative selective arterial embolization followed by intralesional curettage

Explanation

ABCs in the spine and pelvis are highly vascular and prone to massive intraoperative hemorrhage. Preoperative selective arterial embolization is recommended to significantly reduce blood loss during subsequent intralesional curettage or excision.

Question 6352

Topic: 10. Pathology and Oncology

A 40-year-old female with known polyostotic fibrous dysplasia presents with a painless, deep-seated soft tissue mass in her right thigh. MRI shows a well-circumscribed intramuscular mass that is markedly hyperintense on T2-weighted images. What is the most likely diagnosis of this soft tissue lesion?

. Soft tissue sarcoma
. Intramuscular hemangioma
. Intramuscular myxoma
. Lipoma
. Neurofibroma

Correct Answer & Explanation

. Intramuscular myxoma

Explanation

The association of polyostotic fibrous dysplasia with intramuscular myxomas is known as Mazabraud syndrome. These myxomas are benign, appear bright on T2 MRI, and usually do not require resection unless symptomatic.

Question 6353

Topic: 10. Pathology and Oncology

Which of the following bone tumors is most frequently associated with the development of a secondary aneurysmal bone cyst (ABC)?

. Osteoid osteoma
. Giant cell tumor of bone
. Ewing sarcoma
. Multiple myeloma
. Enchondroma

Correct Answer & Explanation

. Giant cell tumor of bone

Explanation

Secondary ABCs occur in pre-existing bone lesions, with Giant Cell Tumor (GCT) of bone being the most common precursor. Other common precursors include chondroblastoma and osteoblastoma.

Question 6354

Topic: 10. Pathology and Oncology

A 16-year-old female presents with an aggressively expanding, painful lytic lesion in her distal fibula with a very thin cortical shell. Biopsy confirms a solid variant of an aneurysmal bone cyst. Which molecular marker definitively distinguishes this primary solid ABC from a giant cell tumor of bone?

. H3F3A mutation
. MDM2 amplification
. USP6 rearrangement
. GNAS mutation
. EXT1 mutation

Correct Answer & Explanation

. USP6 rearrangement

Explanation

Primary ABCs (including the solid variant, which lacks large cystic spaces) consistently show USP6 gene rearrangements. In contrast, Giant Cell Tumors of bone are characterized by H3F3A mutations.

Question 6355

Topic: 10. Pathology and Oncology

A 55-year-old patient with a history of fibrous dysplasia treated 20 years ago presents with rapid swelling, severe pain, and cortical destruction at the previous site. What historical treatment factor most significantly increased this patient's risk for malignant transformation?

. Multiple prior surgeries using intramedullary nails
. Use of allograft bone chips
. Prior radiation therapy
. Long-term bisphosphonate use
. Concurrent diagnosis of Mazabraud syndrome

Correct Answer & Explanation

. Prior radiation therapy

Explanation

Malignant transformation in fibrous dysplasia is rare (<1%). However, a history of prior radiation therapy to the lesion significantly increases the risk of malignant degeneration, most commonly to osteosarcoma or fibrosarcoma.

Question 6356

Topic: Bone Tumors

A radiologist describes a benign-appearing, expansile, diaphyseal radiolucent lesion with a "rind" of reactive sclerosis on the radiograph of a 30-year-old. This typical "rind" sign is most pathognomonic for which of the following conditions?

. Non-ossifying fibroma
. Chondromyxoid fibroma
. Fibrous dysplasia
. Aneurysmal bone cyst
. Simple bone cyst

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

Fibrous dysplasia lesions are typically diaphyseal or metadiaphyseal, exhibiting a "ground-glass" matrix and often surrounded by a thick, sclerotic rim of reactive bone known as the "rind" sign.

Question 6357

Topic: 10. Pathology and Oncology

A 14-year-old girl presents with knee pain. MRI reveals an eccentric, expansile metaphyseal lesion in the proximal tibia with multiple fluid-fluid levels. Genetic testing of the tissue would most likely reveal which of the following?

. USP6 gene rearrangement
. GNAS mutation
. H3F3A mutation
. MDM2 amplification
. SS18-SSX translocation

Correct Answer & Explanation

. USP6 gene rearrangement

Explanation

Primary aneurysmal bone cysts (ABCs) are neoplastic processes driven by rearrangements of the USP6 gene on chromosome 17. The classic MRI finding is multiple fluid-fluid levels representing blood breakdown products.

Question 6358

Topic: Bone Tumors

An 8-year-old girl is diagnosed with polyostotic fibrous dysplasia. She has large cafe-au-lait spots with irregular borders on her trunk. Which of the following endocrine abnormalities is most commonly associated with her condition?

. Hypothyroidism
. Diabetes mellitus
. Precocious puberty
. Hypoparathyroidism
. Adrenal insufficiency

Correct Answer & Explanation

. Precocious puberty

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, cafe-au-lait spots with coast of Maine borders, and endocrinopathies. The most common endocrine manifestation is precocious puberty.

Question 6359

Topic: Bone Tumors

Which of the following surgical techniques is considered the gold standard for managing a symptomatic shepherd's crook deformity in a patient with polyostotic fibrous dysplasia?

. Curettage and bone grafting with cancellous allograft
. Valgus producing osteotomy stabilized with a plate and screws
. Valgus producing osteotomy stabilized with an intramedullary nail
. Resection and endoprosthetic reconstruction
. Radiation therapy followed by casting

Correct Answer & Explanation

. Valgus producing osteotomy stabilized with an intramedullary nail

Explanation

Cortical bone replacement via intramedullary nailing combined with a valgus osteotomy is the most reliable treatment for a shepherd's crook deformity. Plating has a high failure rate, and bone grafts tend to resorb.

Question 6360

Topic: Bone Tumors

Histopathological examination of a proximal femoral lesion demonstrates woven bone trabeculae in a fibrous stroma without osteoblastic rimming. What radiographic feature is most characteristic of this condition?

. Sunburst periosteal reaction
. Epiphyseal location crossing the physis
. Well-circumscribed intramedullary lesion with a ground-glass matrix
. Soap-bubble appearance with cortical breakthrough
. Popcorn calcifications

Correct Answer & Explanation

. Well-circumscribed intramedullary lesion with a ground-glass matrix

Explanation

The histology is pathognomonic for fibrous dysplasia, displaying Chinese character trabeculae. The classic radiographic finding is a well-circumscribed medullary lesion with a ground-glass appearance.

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