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10. Pathology and Oncology MCQs

Practice Set 319 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 6361

Topic: 10. Pathology and Oncology

A patient with polyostotic fibrous dysplasia develops multiple intramuscular masses in the right thigh adjacent to the bony lesions. Biopsy of the soft tissue masses reveals a hypocellular, myxoid stroma with spindle cells. What is the eponym for this clinical presentation?

. Ollier disease
. Maffucci syndrome
. McCune-Albright syndrome
. Mazabraud syndrome
. Klippel-Trenaunay syndrome

Correct Answer & Explanation

. Mazabraud syndrome

Explanation

Mazabraud syndrome is the rare association of polyostotic fibrous dysplasia with intramuscular myxomas. These benign soft tissue masses are typically found in the same anatomic region as the bony lesions.

Question 6362

Topic: 10. Pathology and Oncology

During a biopsy of a suspected aneurysmal bone cyst (ABC) in the distal femur, which of the following secondary lesions must the pathologist most carefully rule out due to its frequent harboring of secondary ABCs?

. Osteoid osteoma
. Giant cell tumor of bone
. Ewing sarcoma
. Multiple myeloma
. Fibrous cortical defect

Correct Answer & Explanation

. Giant cell tumor of bone

Explanation

Secondary ABCs can develop within several primary bone tumors, most notably giant cell tumor (GCT) of bone, chondroblastoma, and osteoblastoma. The pathologist must examine the tissue thoroughly to rule out an underlying GCT.

Question 6363

Topic: 10. Pathology and Oncology

A 25-year-old male with a history of monostotic fibrous dysplasia presents with a rapidly enlarging mass and severe pain in his humerus. He received radiation therapy for the lesion 10 years ago. Which of the following is the most likely diagnosis?

. Secondary aneurysmal bone cyst
. Osteomyelitis
. Pathologic fracture through the cyst
. Malignant transformation to osteosarcoma
. Development of Mazabraud syndrome

Correct Answer & Explanation

. Malignant transformation to osteosarcoma

Explanation

Malignant transformation in fibrous dysplasia is rare (less than 1%) but is significantly associated with prior radiation therapy. The most common histology of the secondary malignancy is osteosarcoma.

Question 6364

Topic: Bone Tumors

An 11-year-old boy undergoes extended intralesional curettage of an aneurysmal bone cyst in the distal tibia. Which of the following is most commonly used during this procedure to reduce the rate of local recurrence?

. Hydrogen peroxide
. High-speed burr and phenol
. Chlorhexidine irrigation
. Intravenous antibiotics
. Methotrexate wash

Correct Answer & Explanation

. High-speed burr and phenol

Explanation

Treatment of ABCs involves extended intralesional curettage, mechanical burring, and chemical or thermal adjuvants like phenol or liquid nitrogen. This multimodal approach effectively kills remaining cyst cells to prevent recurrence.

Question 6365

Topic: 10. Pathology and Oncology

What is the primary role of bisphosphonate therapy in the medical management of symptomatic polyostotic fibrous dysplasia?

. Curative eradication of the dysplastic bone
. Prevention of malignant transformation
. Relief of severe bone pain
. Correction of the shepherd's crook deformity
. Stimulation of osteoblastic rimming

Correct Answer & Explanation

. Relief of severe bone pain

Explanation

Bisphosphonates, such as pamidronate or zoledronic acid, are primarily indicated to manage severe bone pain in fibrous dysplasia. They do not alter disease progression, prevent fractures, or correct structural deformities.

Question 6366

Topic: 10. Pathology and Oncology

An 18-year-old woman is evaluated for a solitary, lytic, expansile lesion in the distal radius. Biopsy demonstrates cavernous blood-filled spaces. Karyotype shows a t(16;17) translocation. What protein is directly upregulated due to this genetic rearrangement?

. Gs-alpha
. USP6
. p53
. Beta-catenin
. RANKL

Correct Answer & Explanation

. USP6

Explanation

The t(16;17) translocation in primary aneurysmal bone cysts fuses the promoter region of CDH11 to the USP6 gene. This causes profound upregulation of USP6, a ubiquitin-specific protease driving the neoplasm.

Question 6367

Topic: Bone Tumors

A 21-year-old female presents with recurrent swelling of her proximal humerus 18 months after curettage of an Aneurysmal Bone Cyst. Which of the following surgical factors is most strongly associated with an increased risk of ABC recurrence?

. Older patient age
. Presence of a USP6 translocation
. Incomplete surgical removal without high-speed burring
. Use of phenol as an adjuvant
. Diaphyseal location

Correct Answer & Explanation

. Incomplete surgical removal without high-speed burring

Explanation

The most significant risk factor for the recurrence of an aneurysmal bone cyst is incomplete intralesional excision. Adding mechanical adjuvants like a high-speed burr significantly decreases the recurrence rate.

Question 6368

Topic: Bone Tumors
A patient with suspected McCune-Albright syndrome exhibits a characteristic café-au-lait spot. How does the macroscopic appearance of this cutaneous lesion typically differ from those seen in Neurofibromatosis type 1 (NF1)?
. They are significantly smaller and more numerous
. They have irregular, jagged borders resembling the coast of Maine
. They are raised and palpable
. They exclusively cross the midline of the body
. They exhibit a smooth, coast of California border

Correct Answer & Explanation

. They have irregular, jagged borders resembling the coast of Maine

Explanation

Café-au-lait spots in McCune-Albright syndrome typically have irregular, jagged borders commonly described as the coast of Maine. In contrast, the lesions in NF1 have smooth borders referred to as the coast of California.

Question 6369

Topic: 10. Pathology and Oncology

A 14-year-old boy undergoes biopsy of an expansile, eccentric lytic lesion in the distal femur. Histology shows blood-filled spaces lined by fibrous septa containing multinucleated giant cells. Which genetic abnormality is pathognomonic for the primary form of this lesion?

. GNAS mutation
. USP6 translocation
. EXT1 mutation
. RUNX2 mutation
. t(11;22) translocation

Correct Answer & Explanation

. USP6 translocation

Explanation

Primary Aneurysmal Bone Cysts (ABCs) are true neoplasms characterized by USP6 gene translocations, most commonly t(16;17)(q22;p13). This distinguishes primary ABCs from secondary ABCs, which lack this genetic marker.

Question 6370

Topic: Bone Tumors

Which of the following MRI findings is highly characteristic, though not entirely specific, for an aneurysmal bone cyst?

. Ground-glass matrix
. Popcorn calcifications
. Fluid-fluid levels
. Intramedullary target sign
. Double-line sign

Correct Answer & Explanation

. Fluid-fluid levels

Explanation

Fluid-fluid levels on MRI represent separated blood components of different densities. While highly characteristic of ABCs, they are not pathognomonic and can also be seen in telangiectatic osteosarcoma and giant cell tumors.

Question 6371

Topic: 10. Pathology and Oncology

Secondary aneurysmal bone cysts can arise within pre-existing osseous lesions. Which of the following benign tumors is most commonly associated with the development of a secondary ABC?

. Osteochondroma
. Giant cell tumor of bone
. Osteoid osteoma
. Enchondroma
. Osteoma

Correct Answer & Explanation

. Giant cell tumor of bone

Explanation

Approximately 30% of ABCs are secondary. Giant cell tumor of bone, chondroblastoma, and osteoblastoma are the most common benign lesions associated with the formation of a secondary ABC.

Question 6372

Topic: Bone Tumors
A 7-year-old girl presents with a limp, irregular café-au-lait spots on her trunk, and a history of early vaginal bleeding. Pelvic radiographs show a lytic ground-glass lesion in the proximal femur. Which endocrine abnormality is most characteristic of this syndrome?
. Precocious puberty
. Hypothyroidism
. Adrenal insufficiency
. Hypoparathyroidism
. Type 1 Diabetes mellitus

Correct Answer & Explanation

. Precocious puberty

Explanation

McCune-Albright syndrome is characterized by the classic triad of polyostotic fibrous dysplasia, café-au-lait macules with "coast of Maine" irregular borders, and hyperfunctioning endocrinopathies, most commonly precocious puberty.

Question 6373

Topic: 10. Pathology and Oncology

An adult female with known polyostotic fibrous dysplasia presents with a painless, slow-growing soft tissue mass in her thigh. A biopsy of the mass reveals a hypocellular lesion with abundant myxoid stroma. What is the diagnosis?

. Liposarcoma
. Synovial sarcoma
. Intramuscular myxoma (Mazabraud syndrome)
. Malignant peripheral nerve sheath tumor
. Neurofibroma

Correct Answer & Explanation

. Intramuscular myxoma (Mazabraud syndrome)

Explanation

Mazabraud syndrome is a rare condition characterized by the association of polyostotic fibrous dysplasia and single or multiple intramuscular myxomas. These soft tissue tumors often occur in the same anatomic region as the severely affected bone.

Question 6374

Topic: Bone Tumors

A 25-year-old man with fibrous dysplasia presents with severe varus deformity of the proximal femur (shepherd's crook) and an impending fracture. Following a corrective valgus osteotomy, which is the most appropriate fixation method?

. Cortical bone grafting alone
. Plate and screw construct
. Intramedullary nailing
. External fixation
. Cancellous allograft packing

Correct Answer & Explanation

. Intramedullary nailing

Explanation

Intramedullary nailing is the preferred fixation method for shepherd's crook deformities in fibrous dysplasia. Plates and screws have a high failure rate due to poor screw purchase in dysplastic bone, and cortical bone grafts are rapidly resorbed by the disease process.

Question 6375

Topic: Bone Tumors

Telangiectatic osteosarcoma can closely mimic an aneurysmal bone cyst on standard MRI. Which histologic feature best differentiates telangiectatic osteosarcoma from a primary ABC?

. Presence of multinucleated giant cells
. Fibrous septa separating blood-filled spaces
. Cytologic atypia of the septal stromal cells
. Presence of hemosiderin-laden macrophages
. Reactive woven bone formation

Correct Answer & Explanation

. Cytologic atypia of the septal stromal cells

Explanation

While both lesions show blood-filled cystic spaces separated by septa, telangiectatic osteosarcoma exhibits marked cytologic atypia, pleomorphism, and atypical mitoses within the septal stromal cells. The fibroblasts in an ABC are inherently benign.

Question 6376

Topic: 10. Pathology and Oncology

Although rare (less than 1%), spontaneous malignant transformation can occur in lesions of fibrous dysplasia. When transformation occurs, which of the following is the most common histologic subtype?

. Chondrosarcoma
. Osteosarcoma
. Ewing sarcoma
. Multiple myeloma
. Adamantinoma

Correct Answer & Explanation

. Osteosarcoma

Explanation

Malignant transformation of fibrous dysplasia is rare but is most commonly identified as osteosarcoma, followed by fibrosarcoma or chondrosarcoma. A history of prior radiation therapy to the lesion significantly increases this risk.

Question 6377

Topic: Bone Tumors

On a standard plain radiograph, fibrous dysplasia typically presents with which of the following classic morphologic appearances?

. Sunburst periosteal reaction with a Codman triangle
. "Onion-skin" periostitis
. Expansile medullary lesion with a "ground-glass" matrix
. Epiphyseal lytic lesion with a thick sclerotic rim
. Dense blastic lesion with a central radiolucent nidus

Correct Answer & Explanation

. Expansile medullary lesion with a "ground-glass" matrix

Explanation

Fibrous dysplasia typically appears as a radiolucent, expansile medullary lesion with a hazy, "ground-glass" matrix. This radiographic appearance directly reflects the histologic replacement of normal cancellous bone by abnormal fibrous tissue and irregular woven bone trabeculae.

Question 6378

Topic: 10. Pathology and Oncology

A 15-year-old boy presents with a pathologic fracture of the proximal femur with a characteristic "shepherd's crook" deformity. Biopsy reveals woven bone trabeculae lacking osteoblastic rimming within a fibrous stroma. What is the underlying genetic mechanism of this condition?

. t(16;17) translocation involving the USP6 gene
. Mutation in the EXT1 gene
. Activating mutation in the GNAS gene causing increased cAMP
. Inactivating mutation in the NF1 gene
. Mutation in the FGFR3 gene

Correct Answer & Explanation

. Activating mutation in the GNAS gene causing increased cAMP

Explanation

The clinical and histologic description is classic for fibrous dysplasia. This condition is caused by an activating missense mutation in the GNAS gene, which encodes the alpha subunit of the Gs G-protein, leading to elevated intracellular cAMP.

Question 6379

Topic: 10. Pathology and Oncology

A 14-year-old boy has an expansile, eccentric, radiolucent lesion in the proximal tibial metaphysis. MRI demonstrates multiple fluid-fluid levels. Cytogenetic analysis is most likely to reveal an abnormality involving which of the following?

. t(11;22) translocation
. t(16;17) translocation
. MDM2 amplification
. H3F3A mutation
. GNAS mutation

Correct Answer & Explanation

. t(11;22) translocation

Explanation

The presence of a metaphyseal expansile lesion with MRI fluid-fluid levels strongly suggests an aneurysmal bone cyst (ABC). Primary ABCs are characterized by translocations involving the USP6 gene on chromosome 17, most commonly t(16;17).

Question 6380

Topic: Bone Tumors
A 9-year-old girl is found to have polyostotic fibrous dysplasia, café-au-lait spots with irregular borders, and precocious puberty. Which of the following is true regarding surgical management of impending fractures in this patient?
. Cortical bone autograft is preferred over allograft
. Plate and screw constructs provide the lowest failure rates
. Intramedullary devices should be used to bypass the entire diseased segment
. Curettage and isolated bone grafting is the treatment of choice
. Surgical intervention is contraindicated until skeletal maturity

Correct Answer & Explanation

. Intramedullary devices should be used to bypass the entire diseased segment

Explanation

Patients with McCune-Albright syndrome have polyostotic fibrous dysplasia, which produces structurally weak bone. Fixation requires load-sharing intramedullary devices spanning the entire lesion; plates/screws and isolated autografts have unacceptably high failure rates due to bone resorption.

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