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10. Pathology and Oncology MCQs

Practice Set 350 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 6981

Topic: 10. Pathology and Oncology

A 60-year-old man undergoes a biopsy for a permeative lesion of the proximal femur.

Histology demonstrates sheets of large, atypical mononuclear cells with prominent nucleoli. Immunohistochemistry is strongly positive for CD20 and CD45, but negative for CD99 and CD138. What is the most appropriate next step in systemic evaluation?

. Serum protein electrophoresis (SPEP) and urine Bence Jones protein
. PET/CT scan of the chest, abdomen, and pelvis for staging
. Translocation t(11;22) testing via FISH for targeted therapy
. Prostate-specific antigen (PSA) and technetium-99m bone scan
. MRI of the entire neuroaxis to rule out drop metastases

Correct Answer & Explanation

. PET/CT scan of the chest, abdomen, and pelvis for staging

Explanation

The CD20 and CD45 positivity confirms diffuse large B-cell lymphoma (primary bone lymphoma), while negative CD138 rules out multiple myeloma and negative CD99 makes Ewing sarcoma unlikely. Staging via PET/CT is the standard next step.

Question 6982

Topic: Bone Tumors
A 7-year-old girl presents with a limp and a noticeable leg-length discrepancy. Radiographs reveal a 'shepherd's crook' deformity of the proximal femur with a characteristic ground-glass appearance in the medullary canal. Physical examination shows irregular, 'coast of Maine' café-au-lait spots on her torso. Which of the following endocrine abnormalities is most commonly associated with this patient's underlying condition?
. Precocious puberty
. Hypothyroidism
. Hyperparathyroidism
. Diabetes insipidus
. Adrenal insufficiency

Correct Answer & Explanation

. Precocious puberty

Explanation

This patient presents with the classic triad of McCune-Albright syndrome: polyostotic fibrous dysplasia (shepherd's crook deformity, ground-glass bone lesions), café-au-lait spots with irregular borders ('coast of Maine'), and endocrine hyperfunction. The most common endocrine abnormality in McCune-Albright syndrome is precocious puberty, particularly in females. It is caused by a post-zygotic somatic activating mutation in the GNAS1 gene, leading to overproduction of cAMP.

Question 6983

Topic: 10. Pathology and Oncology

A 14-year-old boy with a known history of multiple hereditary exostoses (MHE) presents with a rapidly enlarging, painful mass on his right proximal tibia. Which of the following genetic mutations and associated malignant transformation risks are most accurate for his underlying condition?

. EXT1 mutation with a 1-5% risk of primary osteosarcoma
. EXT1 mutation with a 1-5% risk of secondary chondrosarcoma
. GNAS1 mutation with a 10% risk of fibrosarcoma
. FGFR3 mutation with a 1-5% risk of chondrosarcoma
. RUNX2 mutation with a 10% risk of osteosarcoma

Correct Answer & Explanation

. EXT1 mutation with a 1-5% risk of secondary chondrosarcoma

Explanation

Correct Answer: EXT1 mutation with a 1-5% risk of secondary chondrosarcomaMultiple Hereditary Exostoses (MHE), also known as diaphyseal aclasis, is an autosomal dominant skeletal dysplasia characterized by multiple osteochondromas. It is caused by mutations in the EXT1 or EXT2 genes, which are tumor suppressor genes involved in heparan sulfate synthesis. The most significant complication is malignant transformation into a secondary chondrosarcoma, which occurs in approximately 1% to 5% of patients. Rapid growth or pain in a previously stable lesion, especially after skeletal maturity, should raise high suspicion for malignancy.

Question 6984

Topic: 10. Pathology and Oncology

A 22-year-old female presents with multiple asymmetric cartilaginous lesions in the metaphyses and diaphyses of her hands and long bones. Physical examination reveals multiple soft tissue hemangiomas with phleboliths visible on radiographs. What is the estimated risk of malignant transformation to chondrosarcoma in this specific syndrome compared to isolated multiple enchondromatosis (Ollier disease)?

. Lower risk than Ollier disease
. Approximately equal to Ollier disease (1-5%)
. Slightly higher risk, approximately 10-15%
. Significantly higher risk, approximately 20-30% or more
. No malignant potential

Correct Answer & Explanation

. Significantly higher risk, approximately 20-30% or more

Explanation

Correct Answer: Significantly higher risk, approximately 20-30% or moreThe patient has Maffucci syndrome, characterized by multiple enchondromatosis associated with soft tissue hemangiomas. While Ollier disease (multiple enchondromatosis alone) carries a risk of malignant transformation to chondrosarcoma (often cited around 5-30% depending on the extent), Maffucci syndrome carries a significantly higher risk. The risk of chondrosarcoma in Maffucci syndrome is generally reported to be between 20% and 30%, and these patients also have a high risk (up to 100% lifetime risk) of developing other non-skeletal malignancies (e.g., astrocytomas, ovarian tumors).

Question 6985

Topic: Bone Tumors

A 12-year-old boy with polyostotic fibrous dysplasia requires surgical intervention for a progressive 'shepherd's crook' deformity of the proximal femur. Which of the following surgical strategies is most appropriate to prevent recurrence and achieve stable fixation?

. Curettage and packing with autologous cancellous bone graft
. Valgus osteotomy stabilized with a dynamic hip screw and side plate
. Valgus osteotomy stabilized with an intramedullary nail
. Resection of the dysplastic bone and replacement with a massive allograft
. Curettage and packing with cortical strut allografts

Correct Answer & Explanation

. Valgus osteotomy stabilized with an intramedullary nail

Explanation

Correct Answer: Valgus osteotomy stabilized with an intramedullary nailSurgical management of the shepherd's crook deformity in fibrous dysplasia is challenging due to poor bone quality. Cortical and cancellous bone grafts (both auto- and allografts) typically resorb and are replaced by dysplastic bone, leading to recurrence. Plate and screw constructs frequently fail because the dysplastic bone cannot hold screws securely. The gold standard treatment is a valgus producing osteotomy to correct the mechanical axis, stabilized with an intramedullary device (like a cephalomedullary nail) that spans the entire length of the affected bone to provide load-sharing support and prevent future fractures.

Question 6986

Topic: 10. Pathology and Oncology

A biopsy is taken from a lytic, expansile lesion in the proximal femur of a 20-year-old patient. The histological examination reveals irregular trabeculae of woven bone arising directly from a fibrous stroma. Notably, there is a distinct lack of osteoblastic rimming around these trabeculae, which are described as resembling 'Chinese characters'. Which of the following is the most likely diagnosis?

. Non-ossifying fibroma
. Osteofibrous dysplasia
. Fibrous dysplasia
. Chondromyxoid fibroma
. Desmoplastic fibroma

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

Correct Answer: Fibrous dysplasiaThe histological description is pathognomonic for fibrous dysplasia. It is characterized by a bland fibrous stroma containing irregular, disconnected trabeculae of woven bone that resemble 'Chinese characters' or 'alphabet soup'. A key distinguishing feature is the absence of osteoblastic rimming around the bone trabeculae. In contrast, osteofibrous dysplasia (which typically occurs in the tibia of young children) features prominent osteoblastic rimming around the bone trabeculae.

Question 6987

Topic: Bone Tumors

A 28-year-old asymptomatic woman undergoes a pelvic radiograph following a minor fall. The radiograph reveals numerous small, well-defined, symmetric sclerotic foci clustered around the periarticular regions of the pelvis and proximal femora. If this patient has an associated skin condition, what is the most likely diagnosis?

. McCune-Albright syndrome
. Mazabraud syndrome
. Buschke-Ollendorff syndrome
. Maffucci syndrome
. Neurofibromatosis type 1

Correct Answer & Explanation

. Buschke-Ollendorff syndrome

Explanation

Correct Answer: Buschke-Ollendorff syndromeThe radiographic findings describe osteopoikilosis ('spotted bone disease'), an asymptomatic, autosomal dominant sclerosing bone dysplasia characterized by numerous small, dense bone islands clustered near the ends of long bones and in the pelvis. When osteopoikilosis is associated with connective tissue nevi of the skin (disseminated lenticularis or dermatofibrosis lenticularis disseminata), the condition is known as Buschke-Ollendorff syndrome. It is associated with mutations in the LEMD3 gene.

Question 6988

Topic: 10. Pathology and Oncology

A 5-year-old boy is diagnosed with Ollier disease. He has multiple cartilaginous lesions predominantly affecting his right lower extremity. Which of the following is the most common orthopedic complication he will likely face during his growing years?

. Pathological fracture of the femoral neck
. Severe limb length discrepancy and angular deformity
. Early-onset osteoarthritis of the hip
. Spontaneous malignant transformation before age 10
. Development of multiple osteochondromas

Correct Answer & Explanation

. Severe limb length discrepancy and angular deformity

Explanation

Correct Answer: Severe limb length discrepancy and angular deformityOllier disease is a non-hereditary disorder characterized by multiple enchondromas, which are benign cartilaginous tumors developing in the metaphyses and diaphyses of bones. The disease often has a unilateral predominance. The presence of these lesions disrupts normal physeal growth, leading to the most common orthopedic complications in childhood: severe limb length discrepancies and angular deformities (such as genu valgum or varum). While malignant transformation to chondrosarcoma is a serious risk, it typically occurs in adulthood, not before age 10.

Question 6989

Topic: Bone Tumors
A 14-year-old girl presents with a progressive 'shepherd's crook' deformity of the proximal femur and large café-au-lait spots with irregular 'coast of Maine' borders. Which of the following genetic mutations is most likely responsible for the anarchic development of bone constituents in this patient?
. Activating mutation in the GNAS1 gene
. Loss-of-function mutation in the EXT1 gene
. Gain-of-function mutation in the FGFR3 gene
. Mutation in the COMP (Cartilage Oligomeric Matrix Protein) gene
. Mutation in the COL1A1 gene

Correct Answer & Explanation

. Activating mutation in the GNAS1 gene

Explanation

This patient presents with McCune-Albright syndrome, characterized by polyostotic fibrous dysplasia, café-au-lait spots with irregular borders, and endocrine abnormalities (such as precocious puberty). Fibrous dysplasia is a classic example of anarchic bone development caused by a somatic, activating mutation in the GNAS1 gene. This mutation leads to increased intracellular cAMP, resulting in the replacement of normal bone and marrow with fibrous tissue and woven bone. EXT1 is associated with multiple hereditary exostoses, FGFR3 with achondroplasia, COMP with pseudoachondroplasia, and COL1A1 with osteogenesis imperfecta.

Question 6990

Topic: 10. Pathology and Oncology

A 22-year-old patient is diagnosed with Maffucci syndrome, a condition characterized by the anarchic development of cartilage within the metaphyses of long bones. Which of the following clinical features distinguishes this condition from Ollier disease?

. Unilateral distribution of enchondromas
. Presence of soft tissue hemangiomas
. Autosomal dominant inheritance pattern
. Lower risk of malignant transformation to chondrosarcoma
. Presence of cutaneous neurofibromas

Correct Answer & Explanation

. Presence of soft tissue hemangiomas

Explanation

Correct Answer: Presence of soft tissue hemangiomasBoth Ollier disease and Maffucci syndrome are non-hereditary forms of enchondromatosis, characterized by multiple enchondromas (anarchic cartilage development). The distinguishing feature of Maffucci syndrome is the concurrent presence of multiple soft tissue hemangiomas (often presenting as bluish subcutaneous nodules). Maffucci syndrome also carries a significantly higher overall risk of malignant transformation (approaching 100% for any malignancy, including chondrosarcoma, astrocytoma, and GI malignancies) compared to Ollier disease (which has an approximately 25-30% risk of chondrosarcoma).

Question 6991

Topic: Bone Tumors

Which of the following radiographic descriptions is the classic hallmark of fibrous dysplasia?

. 'Erlenmeyer flask' deformity of the distal femur
. 'Ground-glass' appearance with a well-defined sclerotic margin
. 'Sunburst' periosteal reaction with Codman's triangle
. 'Blade of grass' or 'flame-shaped' lucency in the diaphysis
. 'Picture frame' vertebral bodies

Correct Answer & Explanation

. 'Ground-glass' appearance with a well-defined sclerotic margin

Explanation

Correct Answer: 'Ground-glass' appearance with a well-defined sclerotic marginThe classic radiographic hallmark of fibrous dysplasia is a radiolucent, 'ground-glass' appearance. This occurs because the normal trabecular bone is replaced by a homogeneous, gritty fibrous tissue containing microscopic spicules of woven bone, which scatters x-rays to create the hazy, ground-glass look. The lesions are typically intramedullary, expansile, and surrounded by a thick sclerotic rim (rind). 'Erlenmeyer flask' deformity is seen in Gaucher disease and osteopetrosis; 'Sunburst' is classic for osteosarcoma; 'Blade of grass' and 'Picture frame' vertebrae are seen in Paget's disease.

Question 6992

Topic: 10. Pathology and Oncology

A 35-year-old male presents with chronic, deep aching pain in his left lower extremity and decreased range of motion in his knee. Radiographs reveal dense, irregular, eccentric hyperostosis along the cortex of the femur and tibia, resembling 'dripping candle wax'. Which of the following is true regarding this condition?

. It is typically bilateral and symmetric
. It is associated with a high rate of malignant transformation to osteosarcoma
. It is caused by a somatic mutation in the MAP2K1 or LEMD3 gene
. The primary treatment is wide surgical resection
. It predominantly affects the axial skeleton

Correct Answer & Explanation

. It is caused by a somatic mutation in the MAP2K1 or LEMD3 gene

Explanation

Correct Answer: It is caused by a somatic mutation in the MAP2K1 or LEMD3 geneThe clinical and radiographic presentation ('dripping candle wax' hyperostosis) is pathognomonic for melorheostosis. This is a rare, non-hereditary sclerosing bone dysplasia characterized by anarchic cortical thickening. Recent genetic studies have linked melorheostosis to somatic mutations in the MAP2K1 gene (in isolated cases) or the LEMD3 gene (especially when associated with osteopoikilosis or Buschke-Ollendorff syndrome). It is typically unilateral, affects the appendicular skeleton, has no malignant potential, and is managed symptomatically (surgery is reserved for severe contractures or deformities).

Question 6993

Topic: Bone Tumors

An incidental radiographic finding in a 40-year-old woman shows numerous small, well-defined, symmetric sclerotic foci clustered around the periarticular regions of her long bones, pelvis, and carpal bones. She is completely asymptomatic. If this patient has an associated skin condition, what is the most likely diagnosis?

. McCune-Albright syndrome
. Buschke-Ollendorff syndrome
. Mazabraud syndrome
. Neurofibromatosis type 1
. Tuberous sclerosis

Correct Answer & Explanation

. Buschke-Ollendorff syndrome

Explanation

Correct Answer: Buschke-Ollendorff syndromeThe radiographic findings describe osteopoikilosis ('spotted bone disease'), an asymptomatic, autosomal dominant sclerosing dysplasia. When osteopoikilosis is associated with disseminated connective tissue nevi (skin lesions), the condition is known as Buschke-Ollendorff syndrome. Both isolated osteopoikilosis and Buschke-Ollendorff syndrome are associated with loss-of-function mutations in the LEMD3 gene.

Question 6994

Topic: 10. Pathology and Oncology

A 20-year-old male with monostotic fibrous dysplasia of the proximal femur presents with increasing pain and a progressive 'shepherd's crook' deformity. Surgical intervention is planned. Which of the following principles is most appropriate for the surgical management of this lesion?

. Curettage and packing with autologous cancellous bone graft
. En bloc resection and endoprosthetic reconstruction
. Valgus osteotomy and internal fixation with cortical strut allografts
. Radiation therapy followed by limited curettage
. Intralesional injection of corticosteroids

Correct Answer & Explanation

. Valgus osteotomy and internal fixation with cortical strut allografts

Explanation

Correct Answer: Valgus osteotomy and internal fixation with cortical strut allograftsThe surgical management of fibrous dysplasia in the proximal femur (shepherd's crook deformity) aims to correct the mechanical axis and prevent recurrent fracture. Valgus osteotomy is required to restore normal biomechanics. When grafting is necessary, cortical bone grafts (strut allografts) are strongly preferred over cancellous autografts. Cancellous bone is rapidly resorbed by the host and replaced by dysplastic fibrous tissue, leading to high failure rates. Cortical grafts undergo slower creeping substitution and provide lasting structural support. Radiation therapy is contraindicated due to the risk of malignant transformation.

Question 6995

Topic: 10. Pathology and Oncology
A 45-year-old female with known 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 lesion that is hyperintense on T2-weighted images and hypointense on T1-weighted images. Biopsy confirms an intramuscular myxoma. What is the eponym for this specific association?
. McCune-Albright syndrome
. Maffucci syndrome
. Mazabraud syndrome
. Jaffe-Campanacci syndrome
. Gardner syndrome

Correct Answer & Explanation

. Mazabraud syndrome

Explanation

Mazabraud syndrome is a rare disorder characterized by the association of fibrous dysplasia (usually polyostotic) and one or multiple intramuscular myxomas. The myxomas typically occur in the same anatomic region as the most severely affected bones. Like isolated fibrous dysplasia, Mazabraud syndrome is associated with somatic mutations in the GNAS gene. Jaffe-Campanacci syndrome is the association of multiple non-ossifying fibromas with café-au-lait spots.

Question 6996

Topic: Bone Tumors
A 12-year-old girl presents with a progressive shepherd's crook deformity of the proximal femur and café-au-lait spots with irregular 'coast of Maine' borders. The underlying pathophysiology of her bone lesions is most directly related to a somatic mutation affecting which of the following?
. Fibroblast growth factor receptor 3 (FGFR3)
. Gs alpha protein (GNAS)
. Exostosin-1 (EXT1)
. Isocitrate dehydrogenase 1 (IDH1)
. Cartilage oligomeric matrix protein (COMP)

Correct Answer & Explanation

. Gs alpha protein (GNAS)

Explanation

This patient presents with McCune-Albright syndrome, a severe form of polyostotic fibrous dysplasia associated with café-au-lait spots (irregular borders) and endocrinopathies (e.g., precocious puberty). The condition is caused by a somatic, post-zygotic activating mutation in the GNAS gene. This mutation leads to constitutive activation of the Gs alpha protein, resulting in increased intracellular cAMP levels. This overactivity disrupts normal osteoblast differentiation, leading to the replacement of normal bone with fibrous tissue and immature woven bone. FGFR3 mutations are seen in achondroplasia. EXT1 mutations cause multiple hereditary exostoses. IDH1/2 mutations are associated with Ollier disease and Maffucci syndrome. COMP mutations are seen in pseudoachondroplasia and multiple epiphyseal dysplasia.

Question 6997

Topic: 10. Pathology and Oncology

A 25-year-old male with a history of multiple asymmetric cartilaginous lesions in the phalanges presents with newly enlarging, compressible, bluish subcutaneous nodules on his hands. Which of the following is the most accurate statement regarding his condition compared to isolated multiple enchondromatosis (Ollier disease)?

. It is inherited in an autosomal dominant pattern.
. The risk of malignant transformation to chondrosarcoma is significantly lower.
. It carries a significantly higher risk of concomitant visceral malignancies.
. The primary genetic defect involves the EXT1 gene.
. The bone lesions typically resolve spontaneously after skeletal maturity.

Correct Answer & Explanation

. It carries a significantly higher risk of concomitant visceral malignancies.

Explanation

Correct Answer: It carries a significantly higher risk of concomitant visceral malignancies.The patient has Maffucci syndrome, characterized by multiple enchondromas associated with soft tissue hemangiomas (bluish, compressible nodules). Both Ollier disease and Maffucci syndrome are non-hereditary (somatic mosaicism) and are linked to IDH1/IDH2 mutations. However, Maffucci syndrome carries a much higher risk of malignant transformation. The risk of chondrosarcoma is higher, and crucially, there is a significantly elevated risk of visceral malignancies, including astrocytomas, gastrointestinal, and ovarian carcinomas (approaching a 100% lifetime risk of some malignancy). EXT1 is associated with multiple hereditary exostoses. Enchondromas do not typically resolve spontaneously.

Question 6998

Topic: Bone Tumors

A 10-year-old boy with multiple hereditary exostoses presents with a progressive forearm deformity. Radiographs reveal relative shortening of the ulna, bowing of the radius, and ulnar deviation of the carpus. What is the primary biomechanical cause of this specific forearm deformity?

. Premature closure of the distal radial physis.
. Disproportionate tethering effect due to an osteochondroma at the distal ulnar physis.
. Laxity of the distal radioulnar joint ligaments.
. Overgrowth of the radial head.
. Avascular necrosis of the lunate.

Correct Answer & Explanation

. Disproportionate tethering effect due to an osteochondroma at the distal ulnar physis.

Explanation

Correct Answer: Disproportionate tethering effect due to an osteochondroma at the distal ulnar physis.In Multiple Hereditary Exostoses (MHE), forearm deformities are common and typically present as a Madelung-like deformity. The primary driver is the presence of osteochondromas at the distal ulnar physis. Because the distal ulna contributes a large percentage of the bone's overall longitudinal growth and has a smaller cross-sectional area than the radius, it is disproportionately affected by the tethering effect of the osteochondroma. This leads to ulnar shortening. The continued growth of the radius against the tethered ulna results in radial bowing, secondary radial head subluxation/dislocation, and ulnar deviation of the carpus.

Question 6999

Topic: 10. Pathology and Oncology

A 35-year-old woman presents with chronic, severe aching pain and progressive joint contracture in her right lower extremity. Radiographs demonstrate dense, irregular, eccentric hyperostosis along the cortex of the femur and tibia, resembling 'dripping candle wax'. Which of the following is most characteristic of this condition?

. It typically follows a dermatomal distribution.
. It is strongly associated with precocious puberty.
. The lesions follow a sclerotomal distribution.
. It is caused by a mutation in the GNAS gene.
. Malignant transformation to osteosarcoma occurs in 20% of cases.

Correct Answer & Explanation

. The lesions follow a sclerotomal distribution.

Explanation

Correct Answer: The lesions follow a sclerotomal distribution.The clinical and radiographic presentation is classic for Melorheostosis, a rare, non-hereditary sclerosing bone dysplasia. The hallmark radiographic finding is cortical hyperostosis resembling 'dripping candle wax'. A key characteristic of melorheostosis is that the lesions typically follow a sclerotomal distribution (the zone of the skeleton supplied by a single spinal sensory nerve root), rather than a dermatomal distribution. It is associated with mutations in the LEMD3 gene (also known as MAN1) or MAP2K1. It is not associated with precocious puberty (seen in McCune-Albright) or GNAS mutations. Malignant transformation is exceedingly rare.

Question 7000

Topic: Bone Tumors

A 14-year-old boy with polyostotic fibrous dysplasia requires surgical intervention for a progressive shepherd's crook deformity of the proximal femur. Which of the following surgical strategies is most appropriate to minimize the risk of recurrence and implant failure?

. Curettage and packing with cancellous autograft.
. Valgus osteotomy stabilized with a rigid intramedullary nail.
. Valgus osteotomy stabilized with a laterally applied locking plate.
. Curettage and packing with non-vascularized fibular strut graft.
. Resection of the dysplastic segment and endoprosthetic reconstruction.

Correct Answer & Explanation

. Valgus osteotomy stabilized with a rigid intramedullary nail.

Explanation

Correct Answer: Valgus osteotomy stabilized with a rigid intramedullary nail.Surgical management of the shepherd's crook deformity in fibrous dysplasia is challenging due to the poor mechanical quality of the dysplastic bone. Bone grafting (autograft or allograft) alone is contraindicated because the host bone will resorb the graft and replace it with more dysplastic bone. Extramedullary fixation (plates and screws) has a high failure rate because the screws pull out of the weak bone, and the plate acts as a stress riser. The gold standard is a valgus osteotomy to correct the mechanical axis, stabilized with a rigid intramedullary device (like a cephalomedullary nail). This load-sharing construct bypasses the mechanically weak bone and spans the entire length of the femur, significantly reducing the risk of implant failure and recurrent deformity.

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