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Bone Tumors MCQs

Practice Set 50 of 52

This practice set contains high-yield board review questions covering key concepts in Bone Tumors. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 981

Topic: Bone Tumors

Multiple Hereditary Exostoses (MHE) is characterized by multiple osteochondromas throughout the skeleton. Mutations in the EXT1 and EXT2 genes are causative. What is the primary molecular function impaired by these mutations?

. Wnt/beta-catenin signaling regulation
. Tyrosine kinase receptor activation
. Heparan sulfate proteoglycan biosynthesis
. DNA mismatch repair
. Fibroblast growth factor (FGF) receptor binding

Correct Answer & Explanation

. Heparan sulfate proteoglycan biosynthesis

Explanation

EXT1 and EXT2 encode glycosyltransferases essential for the synthesis of heparan sulfate. Defective heparan sulfate synthesis disrupts normal physeal signaling, leading to abnormal cartilage proliferation and osteochondroma formation.

Question 982

Topic: Bone Tumors

An osteochondroma is defined as a cartilage-capped exostosis.

Which of the following imaging features is pathognomonic and strictly required for the diagnosis of an osteochondroma?

. Calcification within the cartilage cap
. Medullary and cortical continuity with the underlying native bone
. A pedunculated morphology pointing away from the joint
. An associated overlying fluid-filled bursa
. A location confined to the metaphysis

Correct Answer & Explanation

. Medullary and cortical continuity with the underlying native bone

Explanation

The hallmark imaging finding that defines an osteochondroma, distinguishing it from other surface osseous lesions, is the direct continuity of its medullary cavity and cortical bone with those of the host bone.

Question 983

Topic: Bone Tumors

Multiple hereditary exostoses (MHE) is an autosomal dominant condition linked to mutations in EXT1 and EXT2. These genes encode for glycosyltransferases primarily involved in the synthesis of which of the following?

. Chondroitin sulfate
. Heparan sulfate
. Hyaluronic acid
. Keratan sulfate
. Type II collagen

Correct Answer & Explanation

. Heparan sulfate

Explanation

EXT1 and EXT2 encode for glycosyltransferases responsible for the synthesis of heparan sulfate proteoglycans. A deficiency in heparan sulfate disrupts Indian hedgehog (Ihh) signaling at the growth plate, triggering the formation of osteochondromas.

Question 984

Topic: Bone Tumors

What is the most definitive pathognomonic radiographic and histologic feature of an osteochondroma?

. A distinct sclerotic margin separating the lesion from the host bone
. Direct cortical and medullary continuity with the underlying host bone
. Intramedullary stippled calcifications known as 'rings and arcs'
. A sunburst periosteal reaction with a Codman triangle
. A radiolucent nidus surrounded by intense reactive sclerosis

Correct Answer & Explanation

. Direct cortical and medullary continuity with the underlying host bone

Explanation

The pathognomonic hallmark of an osteochondroma is the direct continuity of both the cortex and the medullary cavity of the lesion with that of the underlying host bone. This feature distinguishes it from other surface-based osseous lesions.

Question 985

Topic: Bone Tumors

A 16-year-old male presents with a painless, palpable mass about the distal femur.

Which radiographic finding is considered pathognomonic for this lesion?

. Cortical breakthrough with soft tissue extension
. Endosteal scalloping greater than 2/3 of the cortical thickness
. Continuity of the medullary marrow and cortex with the underlying host bone
. Sunburst periosteal reaction with Codman triangle
. A radiolucent nidus surrounded by dense reactive sclerosis

Correct Answer & Explanation

. Continuity of the medullary marrow and cortex with the underlying host bone

Explanation

The diagnosis is an osteochondroma. The hallmark radiographic and histological feature is the direct continuity of the lesion's cortex and medullary cavity with that of the native host bone.

Question 986

Topic: Bone Tumors

A 9-year-old boy presents with multiple bony protuberances, sparse hair, a bulbous nose, and mild intellectual disability. Radiographs confirm multiple hereditary exostoses (osteochondromas). Which of the following chromosomal microdeletions is responsible for this specific syndrome?

. 15q11-q13
. 22q11.2
. 8q24.1
. 5p15.2
. 4p16.3

Correct Answer & Explanation

. 8q24.1

Explanation

The patient has Langer-Giedion syndrome (TRPS Type II). It is caused by a contiguous gene deletion syndrome at chromosome 8q24.1 that encompasses both the TRPS1 gene (causing TRPS features) and the EXT1 gene (causing multiple osteochondromas).

Question 987

Topic: Bone Tumors

A 45-year-old male presents with recurrent non-union of a transverse femur fracture. Radiographs show diffusely thickened cortices and an obliterated medullary canal. History reveals he suffers from frequent sinus infections and has a sibling with similar skeletal findings. What hematologic complication is most likely to develop in this patient?

. Polycythemia vera
. Myelophthisic anemia and extramedullary hematopoiesis
. Acute lymphoblastic leukemia
. Hemophilia A
. Multiple myeloma

Correct Answer & Explanation

. Myelophthisic anemia and extramedullary hematopoiesis

Explanation

The patient has osteopetrosis. Because the osteoclasts fail to resorb bone, the medullary cavity is obliterated by unresorbed primary spongiosa, leading to myelophthisis (marrow failure), pancytopenia, and secondary extramedullary hematopoiesis (hepatosplenomegaly).

Question 988

Topic: Bone Tumors

What is the most common secondary malignancy arising in a patient with long-standing Paget's disease of bone?

. Chondrosarcoma
. Osteosarcoma
. Multiple myeloma
. Ewing sarcoma
. Fibrosarcoma

Correct Answer & Explanation

. Osteosarcoma

Explanation

Osteosarcoma is the most common secondary malignancy in Paget's disease, occurring in approximately 1% of patients. It typically presents with new, severe pain and cortical destruction.

Question 989

Topic: Bone Tumors

TRPS type II (Langer-Giedion syndrome) differs from TRPS type I by the presence of which of the following additional skeletal manifestations?

. Multiple osteochondromas
. Osteopoikilosis
. Fibrous dysplasia
. Enchondromatosis
. Melorheostosis

Correct Answer & Explanation

. Multiple osteochondromas

Explanation

TRPS type II involves a contiguous gene deletion affecting both the TRPS1 and EXT1 genes. The deletion of EXT1 leads to the development of multiple hereditary exostoses (osteochondromas).

Question 990

Topic: Bone Tumors

A 10-year-old boy presents with sparse hair, a bulbous nose, and multiple bony exostoses on his long bones. Hand radiographs show cone-shaped epiphyses. This specific syndrome (Langer-Giedion syndrome) is caused by a contiguous gene deletion involving TRPS1 and which other gene?

. EXT1
. EXT2
. TCIRG1
. SQSTM1
. CLCN7

Correct Answer & Explanation

. EXT1

Explanation

Langer-Giedion syndrome (TRPS Type II) is a contiguous gene syndrome caused by the deletion of both the TRPS1 gene and the EXT1 gene on chromosome 8q24. This explains the combination of Trichorhinophalangeal features and multiple osteochondromas.

Question 991

Topic: Bone Tumors

An 18-year-old presents with a painless mass at the proximal medial tibia.

Which of the following radiographic or MRI findings is the absolute sine qua non for diagnosing a true osteochondroma?

. A calcified cartilage cap exceeding 3 cm
. Periosteal reaction with a Codman triangle
. Continuity of the medullary cavity and cortex of the lesion with the host bone
. A radiolucent nidus surrounded by reactive sclerosis
. Invasion of the adjacent neurovascular bundle

Correct Answer & Explanation

. Continuity of the medullary cavity and cortex of the lesion with the host bone

Explanation

The pathognomonic imaging feature of an osteochondroma is direct cortico-medullary continuity with the native host bone. This helps differentiate it from surface lesions like parosteal osteosarcoma.

Question 992

Topic: Bone Tumors

Which of the following is a strict diagnostic requirement for the radiographic identification of a benign osteochondroma?

. Separation from the host bone medullary canal by a thick sclerotic rim
. Medullary and cortical continuity with the underlying host bone
. Presence of a thick, layered "onion skin" periosteal reaction
. Intralesional popcorn calcification with cortical destruction
. A central nidus measuring less than 1.5 cm with surrounding sclerosis

Correct Answer & Explanation

. Medullary and cortical continuity with the underlying host bone

Explanation

The pathognomonic radiographic hallmark of an osteochondroma is direct continuity of its cortex and medullary cavity with the cortex and medullary cavity of the host bone.

Question 993

Topic: Bone Tumors

A 12-year-old boy presents with a hard, painless bump on his distal femur. Radiographs show a pedunculated bony exostosis pointing away from the joint.

What is the pathognomonic radiographic feature required to confirm an osteochondroma?

. Cortical expansion with ground-glass matrix
. Medullary and cortical continuity with the host bone
. Sunburst periosteal reaction
. A radiolucent nidus surrounded by dense reactive sclerosis
. Stippled calcifications confined to the epiphysis

Correct Answer & Explanation

. Medullary and cortical continuity with the host bone

Explanation

The hallmark of an osteochondroma is the direct continuity of both the cortex and the medullary cavity of the lesion with those of the underlying host bone.

Question 994

Topic: Bone Tumors

A 10-year-old boy presents with an incidentally discovered sessile osteochondroma of the proximal humerus. Over the next several years of skeletal growth, how will the relative position of this lesion change?

. It will migrate toward the diaphysis as the bone elongates.
. It will migrate toward the epiphysis.
. It will slowly invade the joint space.
. It will migrate anteriorly due to muscular traction.
. It will remain completely stationary relative to the physis.

Correct Answer & Explanation

. It will migrate toward the diaphysis as the bone elongates.

Explanation

Osteochondromas arise from aberrant physeal cartilage. As the host bone undergoes longitudinal growth at the physis, the osteochondroma is progressively 'left behind,' making it appear to migrate towards the diaphysis over time.

Question 995

Topic: Bone Tumors

An osteochondroma is generally considered to stop growing at skeletal maturity. If an osteochondroma-like lesion originates within the epiphysis rather than the metaphysis, leading to joint deformity and restricted motion, what is this condition termed?

. Ollier disease
. Maffucci syndrome
. Trevor disease (Dysplasia epiphysealis hemimelica)
. Osgood-Schlatter disease
. Blount disease

Correct Answer & Explanation

. Trevor disease (Dysplasia epiphysealis hemimelica)

Explanation

Trevor disease, or dysplasia epiphysealis hemimelica, is characterized by an osteochondroma-like growth arising from the epiphysis, typically affecting one side (hemimelic) of a joint in the lower extremity. It leads to joint asymmetry, restricted motion, and premature osteoarthritis.

Question 996

Topic: Bone Tumors

A 25-year-old male with a known distal femur osteochondroma presents with a rapidly enlarging, pulsatile popliteal mass and calf pain.

What is the most likely etiology of the new mass?

. Malignant transformation to secondary chondrosarcoma
. Deep vein thrombosis
. Pseudoaneurysm of the popliteal artery
. Bursa formation over the osteochondroma
. Popliteal cyst rupture

Correct Answer & Explanation

. Pseudoaneurysm of the popliteal artery

Explanation

Vascular complications, such as pseudoaneurysm formation, can occur due to repetitive friction of an artery over the hard cartilage cap of an osteochondroma. This is most classically described with the popliteal artery adjacent to a distal femoral osteochondroma.

Question 997

Topic: Bone Tumors

A 15-year-old boy presents with a hard mass on his proximal tibia. Radiographs show a sessile bony exostosis pointing away from the joint space.

Which radiographic finding is required to definitively classify this lesion as an osteochondroma?

. Cartilage cap thicker than 2 cm
. A cauliflower-like heavily calcified appearance
. Cortical and medullary continuity with the host bone
. Reactive sclerosis at the base of the lesion
. Absence of periosteal reaction

Correct Answer & Explanation

. Cortical and medullary continuity with the host bone

Explanation

The pathognomonic radiographic feature of an osteochondroma is direct continuity of its cortex and medullary cavity with that of the native host bone. The lesion classically grows in a direction pointing away from the adjacent joint.

Question 998

Topic: Bone Tumors

A 14-year-old girl is evaluated for a painless, hard mass about the medial aspect of the proximal tibia.

Radiographs and MRI confirm the diagnosis of an osteochondroma. Which of the following imaging features is an absolute requirement to confidently make this diagnosis?

. A radiolucent nidus surrounded by reactive sclerosis
. A cartilaginous cap thickness greater than 2 cm
. Direct continuation of the medullary canal and cortex of the lesion with the host bone
. A periosteal reaction featuring Codman's triangle
. Presence of a thick, enhancing fibrous pseudocapsule

Correct Answer & Explanation

. Direct continuation of the medullary canal and cortex of the lesion with the host bone

Explanation

The pathognomonic radiographic and MRI finding for an osteochondroma is the continuity of both the cortex and the medullary canal of the lesion with that of the underlying host bone. A cartilage cap >2 cm in an adult is a warning sign for malignant transformation.

Question 999

Topic: Bone Tumors

During the surgical excision of a symptomatic solitary osteochondroma of the distal femur in a 20-year-old patient, which of the following oncologic principles is most critical to minimize the risk of local recurrence?

. Wide en bloc resection including 2 cm of normal cortical bone
. Complete removal of the cartilaginous cap and overlying perichondrium
. Intralesional curettage followed by phenol application
. Preoperative embolization to minimize bleeding from the cartilaginous cap
. Postoperative adjuvant external beam radiation therapy

Correct Answer & Explanation

. Complete removal of the cartilaginous cap and overlying perichondrium

Explanation

Symptomatic osteochondromas are treated with marginal excision. It is critical to completely excise the entire cartilaginous cap along with its overlying perichondrium; failure to do so leaves active chondrocytes behind, resulting in local recurrence.

Question 1000

Topic: Bone Tumors

A 65-year-old male presents with a painful, destructive lytic lesion in his proximal femur. Laboratory analysis reveals anemia, hypercalcemia, and a prominent M-spike on serum protein electrophoresis. Which imaging modality is currently the most sensitive test for detecting systemic skeletal lesions in this patient?

. Technetium-99m bone scan
. Whole-body low-dose computed tomography (CT)
. Gallium-67 scan
. Indium-111 leukocyte scan
. Standard plain radiographic skeletal survey

Correct Answer & Explanation

. Whole-body low-dose computed tomography (CT)

Explanation

Whole-body low-dose CT (and whole-body MRI) is much more sensitive than standard plain radiographs for detecting lytic lesions in multiple myeloma. Technetium-99m bone scans rely on osteoblastic activity and are notoriously false-negative in myeloma.

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