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10. Pathology and Oncology MCQs

Practice Set 314 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 6261

Topic: Bone Tumors
A 6-year-old girl is evaluated for a limp and a leg-length discrepancy. Radiographs reveal expansile, ground-glass lesions in her left femur and tibia. Physical examination notes large, hyperpigmented skin macules with irregular borders on her torso. Which of the following endocrine abnormalities is most commonly associated with her likely diagnosis?
. Hypothyroidism
. Precocious puberty
. Hyperparathyroidism
. Diabetes insipidus
. Adrenal insufficiency

Correct Answer & Explanation

. Precocious puberty

Explanation

The patient's presentation of polyostotic fibrous dysplasia and café-au-lait spots with irregular ('coast of Maine') borders is diagnostic of McCune-Albright syndrome. This syndrome is caused by a post-zygotic somatic mutation in the GNAS gene, leading to overactivation of adenylyl cyclase. The most common endocrine abnormality associated with McCune-Albright syndrome is gonadotropin-independent precocious puberty, particularly in females.

Question 6262

Topic: 10. Pathology and Oncology

A 14-year-old patient undergoes knee radiographs for mild anterior knee pain. The images incidentally reveal multiple, fine, linear radiodense striations running parallel to the long axis of the distal femur and proximal tibia metaphyses. The patient has no other systemic symptoms. What is the most likely diagnosis?

. Osteopathia striata
. Osteopoikilosis
. Melorheostosis
. Engelmann disease
. Fibrous dysplasia

Correct Answer & Explanation

. Osteopathia striata

Explanation

Correct Answer: A (Osteopathia striata)Osteopathia striata (Voorhoeve disease) is a benign, usually asymptomatic sclerosing bone dysplasia characterized radiographically by fine, linear, longitudinal radiodense striations in the metaphyses and diaphyses of long bones. It is often an incidental finding. Osteopoikilosis presents as spotty densities, Melorheostosis as 'flowing wax' cortical hyperostosis, and Engelmann disease (progressive diaphyseal dysplasia) presents with fusiform cortical thickening of the diaphyses.

Question 6263

Topic: Bone Tumors

A 12-year-old girl presents with a pathologic fracture of the proximal femur. Radiographs show a 'ground-glass' appearance in the medullary canal with a shepherd's crook deformity. Which of the following genetic mutations is most likely responsible for the underlying condition?

. FGFR3 mutation
. COMP mutation
. GNAS1 mutation
. EXT1 mutation

Correct Answer & Explanation

. GNAS1 mutation

Explanation

Correct Answer: GNAS1 mutationThe clinical and radiographic presentation is classic for fibrous dysplasia. Fibrous dysplasia is caused by a somatic, activating mutation in the GNAS1 gene, which encodes the alpha subunit of the stimulatory G protein (Gs-alpha). This leads to increased intracellular cAMP levels, resulting in abnormal proliferation and differentiation of osteoblasts, replacing normal bone with fibrous stroma and woven bone. FGFR3 mutations are seen in achondroplasia, COMP in pseudoachondroplasia, and EXT1 in multiple hereditary exostoses.

Question 6264

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with multiple asymmetric limb deformities. Radiographs reveal multiple radiolucent lesions in the metaphyses and diaphyses of the long bones and phalanges. Physical examination reveals multiple bluish, compressible soft-tissue masses on the hands and forearms. Which of the following is true regarding his condition compared to patients with isolated multiple enchondromatosis (Ollier disease)?

. It is inherited in an autosomal dominant pattern
. The soft tissue masses are neurofibromas
. There is a significantly higher risk of malignant transformation
. It is caused by a mutation in the EXT1 gene

Correct Answer & Explanation

. There is a significantly higher risk of malignant transformation

Explanation

Correct Answer: There is a significantly higher risk of malignant transformationThe patient has Maffucci syndrome, characterized by multiple enchondromas and soft-tissue hemangiomas. Both Ollier disease and Maffucci syndrome are non-hereditary (somatic mutations, often IDH1/IDH2). Maffucci syndrome carries a much higher risk of malignant transformation (up to 100% lifetime risk for any malignancy, including chondrosarcoma, astrocytoma, and GI malignancies) compared to Ollier disease (approximately 25-30% risk of chondrosarcoma).

Question 6265

Topic: Bone Tumors

A 10-year-old boy presents with multiple bony prominences around his knees and ankles, causing a valgus deformity at the knees. Family history is positive for similar lesions. The pathogenesis of this condition involves a defect in which of the following?

. Type I collagen synthesis
. Heparan sulfate glycosaminoglycan synthesis
. Fibroblast growth factor receptor 3 signaling
. G-protein coupled receptor signaling

Correct Answer & Explanation

. Heparan sulfate glycosaminoglycan synthesis

Explanation

Correct Answer: Heparan sulfate glycosaminoglycan synthesisThe patient has Multiple Hereditary Exostoses (MHE), also known as diaphyseal aclasis. MHE is an autosomal dominant condition caused by mutations in the EXT1 or EXT2 genes. These genes encode glycosyltransferases that are essential for the synthesis of heparan sulfate, a glycosaminoglycan. The deficiency in heparan sulfate disrupts normal Indian hedgehog (Ihh) signaling in the growth plate, leading to the formation of osteochondromas.

Question 6266

Topic: Bone Tumors
An asymptomatic 25-year-old man undergoes a routine pelvic radiograph following a minor trauma. The radiograph incidentally shows numerous small, well-defined, symmetric, periarticular sclerotic foci in the pelvis and proximal femurs. If this patient has an associated skin condition, what is the most likely dermatological finding?
. Café-au-lait spots
. Dermatofibrosis lenticularis disseminata
. Port-wine stains
. Subcutaneous hemangiomas

Correct Answer & Explanation

. Dermatofibrosis lenticularis disseminata

Explanation

The radiographic findings are classic for osteopoikilosis ('spotted bone disease'), an autosomal dominant sclerosing dysplasia caused by LEMD3 mutations. When osteopoikilosis is associated with connective tissue nevi (specifically dermatofibrosis lenticularis disseminata), the condition is known as Buschke-Ollendorff syndrome. Café-au-lait spots are seen in neurofibromatosis and McCune-Albright syndrome. Hemangiomas are seen in Maffucci syndrome.

Question 6267

Topic: Bone Tumors

A 14-year-old boy with polyostotic fibrous dysplasia presents with progressive varus bowing of the proximal femur (shepherd's crook deformity) and increasing thigh pain. What is the most appropriate surgical management for this deformity?

. Curettage and packing with cancellous autograft
. Curettage and packing with cortical allograft
. Valgus producing osteotomy and intramedullary nailing
. Valgus producing osteotomy and plate fixation

Correct Answer & Explanation

. Valgus producing osteotomy and intramedullary nailing

Explanation

Correct Answer: Valgus producing osteotomy and intramedullary nailingIn fibrous dysplasia, the entire bone is often mechanically compromised. Bone grafts (especially cancellous) are typically resorbed and replaced by dysplastic host bone, leading to high failure rates. Plate fixation is also prone to failure due to poor screw purchase in the dysplastic bone and the stress-shielding effect. The gold standard for correcting a shepherd's crook deformity is a valgus-producing osteotomy stabilized with a load-sharing intramedullary device (nail) that spans the entire length of the abnormal bone.

Question 6268

Topic: 10. Pathology and Oncology

A 45-year-old female with a known history of polyostotic fibrous dysplasia presents with a painless, slow-growing soft tissue mass in her right thigh. Magnetic resonance imaging (MRI) reveals a well-circumscribed, intramuscular cystic-appearing lesion with low T1 and high T2 signal intensity. What is the most likely diagnosis of the soft tissue mass?

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

Correct Answer & Explanation

. Intramuscular myxoma

Explanation

Correct Answer: Intramuscular myxomaThe association of fibrous dysplasia with intramuscular myxomas is known as Mazabraud syndrome. These myxomas are benign, slow-growing soft tissue tumors that typically appear in the same anatomical region as the most severely affected bones. On MRI, they appear cystic (low T1, high T2) but enhance with gadolinium. Recognition of this syndrome prevents unnecessary aggressive biopsies or resections for suspected malignancy.

Question 6269

Topic: 10. Pathology and Oncology

A 28-year-old man with a history of multiple hereditary exostoses presents with a new onset of pain and enlargement of a previously stable lesion on his proximal humerus. MRI is performed. Which of the following MRI findings is most concerning for malignant transformation to secondary chondrosarcoma?

. Cartilage cap thickness of 0.5 cm
. Cartilage cap thickness of 2.5 cm
. Continuity of the lesion's marrow cavity with the host bone
. Location of the lesion in the metaphysis

Correct Answer & Explanation

. Cartilage cap thickness of 2.5 cm

Explanation

Correct Answer: Cartilage cap thickness of 2.5 cmPatients with multiple hereditary exostoses have a 1-5% lifetime risk of malignant transformation to secondary chondrosarcoma. Clinical signs include new pain or growth after skeletal maturity. On MRI, a cartilage cap thickness greater than 1.5 to 2.0 cm in an adult is highly suspicious for malignant transformation. Continuity of the marrow cavity is a defining feature of all osteochondromas, benign or malignant.

Question 6270

Topic: Bone Tumors

A 10-year-old girl is evaluated for mild developmental delay and macrocephaly. Radiographs of her lower extremities reveal multiple, parallel, linear bands of sclerosis extending from the metaphyses into the diaphyses of the long bones. Which of the following is the most likely diagnosis?

. Osteopetrosis
. Osteopoikilosis
. Osteopathia striata
. Melorheostosis

Correct Answer & Explanation

. Osteopoikilosis

Explanation

Correct Answer: Osteopathia striataOsteopathia striata (Voorhoeve disease) is a rare sclerosing bone dysplasia characterized radiographically by linear, parallel striations of dense bone in the metaphyses and diaphyses of long bones, and a sunburst appearance in the ilium. It can occur isolated or as part of osteopathia striata with cranial sclerosis (OSCS), an X-linked dominant condition caused by WTX gene mutations, which presents with macrocephaly, cleft palate, and developmental delay.

Question 6271

Topic: Bone Tumors
A 7-year-old girl presents with a history of early breast development and vaginal bleeding. Physical examination reveals large, irregular café-au-lait macules with 'coast of Maine' borders on her trunk. Radiographs show expansile, ground-glass lesions in her left femur and tibia. Which of the following endocrine abnormalities is most commonly associated with this patient's syndrome?
. Hypothyroidism
. Precocious puberty
. Hypoparathyroidism
. Diabetes mellitus

Correct Answer & Explanation

. Precocious puberty

Explanation

The patient has McCune-Albright syndrome, a classic triad of polyostotic fibrous dysplasia, café-au-lait spots (with irregular 'coast of Maine' borders), and endocrine hyperfunction. The most common endocrine abnormality is gonadotropin-independent precocious puberty, especially in females. Other possible endocrine issues include hyperthyroidism, growth hormone excess, and Cushing syndrome.

Question 6272

Topic: 10. Pathology and Oncology

A 5-year-old girl is brought to the clinic due to painful swelling of her neck and back. Examination reveals a shortened great toe with hallux valgus on both feet. Hard, subcutaneous masses are palpated along her paraspinal muscles. What is the most critical management principle for this patient?

. Early surgical excision of the paraspinal masses
. Core needle biopsy to rule out sarcoma
. Avoidance of intramuscular injections and elective surgery
. Initiation of high-dose intravenous bisphosphonates
. Routine manipulation under anesthesia to maintain joint mobility

Correct Answer & Explanation

. Avoidance of intramuscular injections and elective surgery

Explanation

Fibrodysplasia ossificans progressiva (FOP) is characterized by an ACVR1 mutation and classic great toe malformations. Any minor trauma, including biopsies, intramuscular injections, or surgery, triggers explosive heterotopic ossification and must be strictly avoided.

Question 6273

Topic: Soft Tissue Tumors & Metastasis
A 30-year-old patient has routine radiographs following minor trauma that reveal numerous small, symmetric, well-defined sclerotic bone lesions clustered around the periarticular regions of the pelvis and long bones. What associated skin finding is most commonly seen with this condition?
. Café-au-lait macules
. Dermatofibrosis lenticularis disseminata
. Subcutaneous neurofibromas
. Port-wine stains
. Hemangiomas

Correct Answer & Explanation

. Dermatofibrosis lenticularis disseminata

Explanation

Osteopoikilosis (spotted bone disease) is an asymptomatic sclerosing bone dysplasia associated with LEMD3 mutations. It is classically associated with dermatofibrosis lenticularis disseminata (Buschke-Ollendorff syndrome), presenting as connective tissue nevi.

Question 6274

Topic: Bone Tumors

A 15-year-old boy with polyostotic fibrous dysplasia presents with a progressive "shepherd's crook" deformity of the proximal femur and mechanical hip pain. Which surgical construct is most appropriate for stabilizing the femur following corrective osteotomy?

. Non-vascularized fibular strut graft
. Cancellous bone grafting and a dynamic hip screw
. Intramedullary nailing
. External fixation
. Cortical onlay grafting alone

Correct Answer & Explanation

. Intramedullary nailing

Explanation

In fibrous dysplasia, the weak fibro-osseous tissue makes extramedullary plates prone to failure due to poor screw purchase. Intramedullary nailing is the preferred fixation method as it protects the entire length of the bone and effectively unloads the dysplastic cortex.

Question 6275

Topic: 10. Pathology and Oncology

A 60-year-old man with metastatic lung cancer complains of severe, unrelenting pain in his right thigh. Radiographs reveal a 4 cm lytic lesion in the femoral diaphysis that involves approximately 50% of the cortical diameter. According to Mirels' criteria, what is his score and the corresponding recommendation?

. Score 7, observation and radiation therapy
. Score 8, prophylactic fixation is optional
. Score 9, non-weight bearing and chemotherapy
. Score 10, prophylactic internal fixation
. Score 12, immediate amputation

Correct Answer & Explanation

. Score 10, prophylactic internal fixation

Explanation

Mirels' score is calculated based on site (lower limb = 2), pain (severe = 3), type (lytic = 3), and size (1/3 to 2/3 of cortex = 2), totaling 10. A score of 9 or greater indicates a high risk of pathologic fracture, mandating prophylactic fixation.

Question 6276

Topic: 10. Pathology and Oncology

A 45-year-old man undergoes an arthroscopic procedure for chronic knee locking. The surgeon removes dozens of uniformly sized, loose cartilaginous bodies. Which of the following histologic findings is classically associated with the primary form of this disease and must not be misdiagnosed as malignancy?

. Mononuclear cells interspersed with giant cells and hemosiderin deposition
. Cellular atypia, hypercellularity, and binucleate chondrocytes
. Sheets of uniform round cells with glycogen-rich clear cytoplasm
. Spindle cells arranged in a classic herringbone pattern
. Non-calcified hyaline cartilage caps resting on normal bony stalks

Correct Answer & Explanation

. Cellular atypia, hypercellularity, and binucleate chondrocytes

Explanation

Primary synovial chondromatosis characteristically exhibits cellular atypia, hypercellularity, and binucleate cells. Despite these aggressive-appearing features, it is a benign metaplastic condition and should not be mistaken for low-grade chondrosarcoma.

Question 6277

Topic: Bone Tumors

A 15-year-old boy with polyostotic fibrous dysplasia presents with a progressing proximal femur deformity.

Surgical management is planned to restore mechanical alignment. Which of the following is the most appropriate biomechanical approach for reconstruction?

. Cortical onlay allografting with rigid plate fixation
. Curettage, cancellous bone grafting, and dynamic hip screw placement
. Intramedullary nailing utilizing cortical strut grafts
. External fixation for gradual deformity correction
. Resection and megaprosthesis reconstruction

Correct Answer & Explanation

. Intramedullary nailing utilizing cortical strut grafts

Explanation

In fibrous dysplasia, load-sharing intramedullary devices are essential because plates often fail due to the poor quality of the surrounding bone. Additionally, cortical bone grafts are preferred because cancellous grafts are rapidly resorbed and replaced by dysplastic tissue.

Question 6278

Topic: 10. Pathology and Oncology

A 65-year-old man is scheduled for prophylactic intramedullary nailing of a solitary, painful lytic lesion in the right humerus.

Biopsy confirmed metastatic renal cell carcinoma. To prevent a catastrophic intraoperative complication, what critical intervention should be performed 24 to 48 hours prior to surgery?

. Administration of high-dose intravenous bisphosphonates
. Prophylactic internal fixation of the contralateral humerus
. Administration of a RANKL inhibitor (denosumab)
. Selective arterial embolization of the tumor
. Neoadjuvant systemic chemotherapy

Correct Answer & Explanation

. Selective arterial embolization of the tumor

Explanation

Renal cell carcinoma and thyroid carcinoma bone metastases are notoriously hypervascular. Preoperative selective arterial embolization is critical to prevent massive, potentially fatal intraoperative hemorrhage.

Question 6279

Topic: 10. Pathology and Oncology

A 60-year-old woman with a 15-year history of primary synovial chondromatosis of the hip presents with acute worsening of pain and a rapidly enlarging soft tissue mass. Imaging reveals new cortical destruction and marrow invasion. What is the most likely diagnosis?

. Osteosarcoma
. Synovial sarcoma
. Secondary chondrosarcoma
. Malignant fibrous histiocytoma
. Fibrosarcoma

Correct Answer & Explanation

. Secondary chondrosarcoma

Explanation

While rare, primary synovial chondromatosis carries a small risk of malignant transformation into secondary chondrosarcoma. Rapid clinical deterioration, bone destruction, or marrow invasion on MRI should raise suspicion for this transformation.

Question 6280

Topic: 10. Pathology and Oncology

A 35-year-old woman with polyostotic fibrous dysplasia

complains of a painless, deep-seated soft tissue mass in her right thigh. If this mass is associated with her skeletal condition, a biopsy would most likely reveal which of the following?

. Liposarcoma
. Intramuscular myxoma
. Plexiform neurofibroma
. Desmoid tumor
. Synovial sarcoma

Correct Answer & Explanation

. Intramuscular myxoma

Explanation

Mazabraud syndrome is the rare but classic association of polyostotic fibrous dysplasia with single or multiple intramuscular myxomas. These benign soft-tissue tumors usually appear in the same anatomical region as the most severely affected bones.

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