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10. Pathology and Oncology MCQs

Practice Set 11 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 201

Topic: 10. Pathology and Oncology

What is the risk of malignant transformation over the course of a lifetime in a person with fibrous dysplasia:

. 50%
. 25%
. 15%
. 5%
. Less than 1%

Correct Answer & Explanation

. Less than 1%

Explanation

Fibrous dysplasia is a relatively common disorder. The risk of malignant transformation is less than 1%. Many historic cases of malignant transformation with fibrous dysplasia occurred in patients who also received external beam irradiation.

Question 202

Topic: 10. Pathology and Oncology

The most common malignancy arising from transformation of fibrous dysplasia is:

. C hondrosarcoma
. Adamantinoma
. Giant cell tumor
. Osteosarcoma
. Fibrosarcoma

Correct Answer & Explanation

. Osteosarcoma

Explanation

The most common malignancies arising from transformation of fibrous dysplasia are osteosarcoma and malignant fibrous histiocytoma. However, chondrosarcoma, giant cell tumor, adamantinoma, and fibrosarcoma have been reported to result from fibrous dysplasia. Radiation increases the risk of malignant transformation of fibrous dysplasia.

Question 203

Topic: Bone Tumors

The pattern of genetic transmission of polyostotic fibrous dysplasia is best described as:

. Autosomal dominant with high penetrance
. Autosomal dominant with low penetrance
. Autosomal recessive
. Sex-linked dominant
. No genetic transmission (sporadic)

Correct Answer & Explanation

. No genetic transmission (sporadic)

Explanation

Fibrous dysplasia is a sporadic condition. Although there are a few reports of parents and children having fibrous dysplasia, such reports are rare.

Question 204

Topic: Bone Tumors

Which of the following conditions does this computerizd tomography scan (Slide) most likely represent:

. Brodies abscess
. Osteosarcoma
. Fibrous dysplasia
. Osteoid osteoma
. Enchondromas

Correct Answer & Explanation

. Osteoid osteoma

Explanation

This is an osteoid osteoma of the fourth lumbar vertebra in a patient who experienced night pain and relieved the pain with nonsteroidal anti- inflammatory drugs. The location of a sclerotic nidus in the posterior elements of the vertebrae is typical for this disorder. Excision of the osteoid osteoma resulted in prompt pain relief for this patient.

Question 205

Topic: 10. Pathology and Oncology
Based on the clinical photograph (Slide 1) and radiographs (Slide 2) of this 11-year-old boy, which of the following conditions is demonstrated?
. Idiopathic scoliosis
. Fibrous dysplasia
. Tuberous sclerosis
. Neurofibromatosis
. Diastematomyelia

Correct Answer & Explanation

. Neurofibromatosis

Explanation

This patient has many typical features of neurofibromatosis 1: subcutaneous neurofibromas, large 'coast of California' café-au-lait spot with several others, and a dystrophic curve at a young age. Surgery is recommended.

Question 206

Topic: Bone Tumors

Which of the following histologic features best differentiates osteofibrous dysplasia from fibrous dysplasia?

. Presence of a cartilaginous cap
. Osteoblastic rimming of the bone trabeculae
. Biphasic appearance with epithelial cells
. Mosaic pattern of cement lines
. Absence of woven bone

Correct Answer & Explanation

. Osteoblastic rimming of the bone trabeculae

Explanation

Unlike fibrous dysplasia, which lacks osteoblastic rimming around its irregular woven bone trabeculae, osteofibrous dysplasia demonstrates prominent osteoblastic rimming. Both present as fibro-osseous lesions, but this histologic distinction is critical for diagnosis.

Question 207

Topic: Bone Tumors

A 14-year-old boy with polyostotic fibrous dysplasia presents with increasing thigh pain and a severe varus deformity of the proximal femur (Shepherd's crook deformity).

What is the most appropriate surgical management?

. Curettage and bone grafting with allograft
. Open reduction and internal fixation with a dynamic hip screw
. Valgus osteotomy stabilized with an intramedullary nail
. Resection and endoprosthetic reconstruction
. Observation and bisphosphonate therapy

Correct Answer & Explanation

. Valgus osteotomy stabilized with an intramedullary nail

Explanation

The standard surgical treatment for a progressive Shepherd's crook deformity in fibrous dysplasia involves a valgus-producing osteotomy stabilized with a cephalomedullary or intramedullary nail. Cortical bone grafting and plating alone have unacceptably high failure rates in these mechanically inferior bones.

Question 208

Topic: 10. Pathology and Oncology

A 45-year-old woman with known fibrous dysplasia presents with a slow-growing, painless soft tissue mass in her right thigh. MRI reveals a well-circumscribed, lobulated intramuscular lesion that is hyperintense on T2-weighted images. Biopsy confirms an intramuscular myxoma. What is the diagnosis of this associated syndrome?

. McCune-Albright syndrome
. Mazabraud syndrome
. Jaffe-Campanacci syndrome
. Ollier disease
. Maffucci syndrome

Correct Answer & Explanation

. Mazabraud syndrome

Explanation

Mazabraud syndrome is the rare association of single or multiple intramuscular myxomas with polyostotic fibrous dysplasia. The myxomas typically occur in the same anatomic region as the most severely affected bone.

Question 209

Topic: 10. Pathology and Oncology

A 30-year-old male presents with a slowly enlarging, painful mass over the anterior crest of his left tibia. Radiographs show a distinct, eccentrically located, multiloculated lucent lesion in the anterior tibial diaphysis. Biopsy reveals a biphasic pattern of epithelial islands within a fibrous stroma. Immunohistochemistry will most likely be strongly positive for which of the following?

. S-100
. Vimentin only
. Cytokeratin
. Desmin
. CD99

Correct Answer & Explanation

. Cytokeratin

Explanation

The clinical and histologic picture describes an adamantinoma, a low-grade malignant bone tumor predominantly found in the anterior tibia. It is characterized by biphasic histology and positivity for epithelial markers like cytokeratin and epithelial membrane antigen (EMA).

Question 210

Topic: 10. Pathology and Oncology

A 70-year-old patient with long-standing polyostotic Paget's disease presents with a new, rapidly enlarging, painful mass over his proximal humerus. Radiographs show a destructive lytic lesion breaking through the cortex with an associated soft tissue mass. What is the most likely diagnosis?

. Metastatic carcinoma
. Multiple myeloma
. Secondary osteosarcoma
. Chondrosarcoma
. Fibrosarcoma

Correct Answer & Explanation

. Secondary osteosarcoma

Explanation

Secondary osteosarcoma is the most common malignant transformation in patients with Paget's disease, occurring in about 1% of patients. It carries a very poor prognosis and presents as a new, rapidly destructive, painful mass in a previously affected pagetic bone.

Question 211

Topic: 10. Pathology and Oncology

A 45-year-old female presents with multiple bony lesions consistent with fibrous dysplasia. She also notes a slow-growing, painless mass in her thigh. Biopsy of the thigh mass reveals a hypocellular, abundant mucoid stroma. What is the most likely diagnosis for this syndrome?

. McCune-Albright syndrome
. Mazabraud syndrome
. Jaffe-Campanacci syndrome
. Ollier disease
. Maffucci syndrome

Correct Answer & Explanation

. Mazabraud syndrome

Explanation

Mazabraud syndrome is a rare disorder characterized by the association of fibrous dysplasia with one or more intramuscular myxomas. It generally presents in adulthood and carries a slightly increased risk of malignant transformation.

Question 212

Topic: Bone Tumors

A 9-year-old girl with polyostotic fibrous dysplasia presents with precocious puberty and cafe-au-lait spots. What is the underlying genetic mechanism of her condition?

. Mutation in the EXT1 gene
. Mutation in the GNAS1 gene
. Mutation in the NF1 gene
. Mutation in the p53 gene
. Mutation in the RB1 gene

Correct Answer & Explanation

. Mutation in the GNAS1 gene

Explanation

This patient has McCune-Albright syndrome. The condition is caused by an activating somatic missense mutation in the GNAS1 gene, resulting in persistent cAMP production and widespread endocrine, cutaneous, and skeletal abnormalities.

Question 213

Topic: 10. Pathology and Oncology

A biopsy of a proximal femur lesion in a 14-year-old boy shows irregular woven bone trabeculae lacking osteoblastic rimming in a fibrous stroma. What is the most likely diagnosis?

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

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

The histologic hallmark of fibrous dysplasia is irregular, "Chinese character" trabeculae of woven bone embedded in a benign fibrous stroma without osteoblastic rimming.

Question 214

Topic: 10. Pathology and Oncology

A 5-year-old boy presents with anterior bowing of the tibia. Biopsy reveals woven bone trabeculae rimmed by prominent osteoblasts within a fibrous stroma. What is the most likely diagnosis?

. Fibrous dysplasia
. Osteofibrous dysplasia
. Adamantinoma
. Non-ossifying fibroma
. Osteoid osteoma

Correct Answer & Explanation

. Osteofibrous dysplasia

Explanation

Osteofibrous dysplasia occurs almost exclusively in the tibia or fibula of children. It is distinguished from fibrous dysplasia histologically by the presence of prominent osteoblastic rimming around the bone trabeculae.

Question 215

Topic: 10. Pathology and Oncology

Although rare (less than 1%), fibrous dysplasia can undergo malignant transformation. What is the most common histologic subtype of this secondary malignancy?

. Chondrosarcoma
. Osteosarcoma
. Ewing sarcoma
. Fibrosarcoma
. Undifferentiated pleomorphic sarcoma

Correct Answer & Explanation

. Osteosarcoma

Explanation

Malignant transformation in fibrous dysplasia is rare but well-documented, typically associated with prior radiation therapy. Osteosarcoma is the most common secondary malignancy, followed by fibrosarcoma.

Question 216

Topic: Bone Tumors

A 15-year-old boy presents with a prominent limp and shortening of his right leg. Radiographs demonstrate a classic "shepherd's crook" deformity of the proximal femur.

What is the preferred surgical approach for an impending fracture in this patient?

. Curettage and cancellous bone grafting alone
. Cortical strut allograft, valgus-producing osteotomy, and internal fixation
. Wide en bloc resection and endoprosthetic reconstruction
. Percutaneous pinning in situ
. Observation and bracing until skeletal maturity

Correct Answer & Explanation

. Cortical strut allograft, valgus-producing osteotomy, and internal fixation

Explanation

Surgical management of a shepherd's crook deformity requires correction of the mechanical axis via valgus osteotomy and rigid internal fixation. Cortical strut grafts are preferred over cancellous grafts to prevent resorption and recurrence.

Question 217

Topic: Bone Tumors

How do the cafe-au-lait spots seen in McCune-Albright syndrome typically differ from those seen in Neurofibromatosis type 1 (NF1)?

. They have smooth "coast of California" borders
. They have irregular "coast of Maine" borders
. They are predominantly found on the palms and soles
. They are strictly bilateral and symmetrical
. They fade completely after puberty

Correct Answer & Explanation

. They have irregular "coast of Maine" borders

Explanation

Cafe-au-lait macules in McCune-Albright syndrome typically have irregular, jagged borders resembling the "coast of Maine." In contrast, those in NF1 have smooth borders resembling the "coast of California."

Question 218

Topic: Bone Tumors

A 7-year-old boy has an incidentally discovered unicameral bone cyst (UBC) in the proximal humerus. Radiographs show the cyst is located immediately adjacent to the physis. Which of the following best describes this cyst?

. Latent cyst
. Active cyst
. Aneurysmal bone cyst
. Giant cell tumor
. Chondroblastoma

Correct Answer & Explanation

. Active cyst

Explanation

An active UBC is located immediately adjacent to the epiphyseal plate and has a higher risk of interfering with growth or recurring after treatment. A latent cyst has migrated away from the physis into the diaphysis.

Question 219

Topic: Bone Tumors

A 9-year-old boy presents with mild shoulder pain after throwing a baseball. Radiographs reveal a centrally located, lucent lesion in the proximal humerus with a cortical fragment resting dependently within the lesion. What is the most likely diagnosis?

. Aneurysmal bone cyst
. Non-ossifying fibroma
. Unicameral bone cyst
. Osteosarcoma
. Eosinophilic granuloma

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

The "fallen leaf" or "fallen fragment" sign is pathognomonic for a unicameral bone cyst that has sustained a pathologic fracture. It occurs because the cyst cavity is fluid-filled, allowing the cortical fragment to settle at the base.

Question 220

Topic: 10. Pathology and Oncology

A 14-year-old girl presents with knee pain. Radiographs reveal an expansile, eccentric lytic lesion in the distal femur. Biopsy demonstrates blood-filled spaces separated by septa containing fibroblasts, giant cells, and reactive woven bone. What is the diagnosis?

. Unicameral bone cyst
. Aneurysmal bone cyst
. Telangiectatic osteosarcoma
. Giant cell tumor
. Fibrous dysplasia

Correct Answer & Explanation

. Aneurysmal bone cyst

Explanation

The histologic description of blood-filled spaces devoid of an endothelial lining, separated by fibrous septa containing multinucleated giant cells and woven bone, is the classic appearance of an Aneurysmal Bone Cyst (ABC).

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