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10. Pathology and Oncology MCQs

Practice Set 39 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 761

Topic: 10. Pathology and Oncology

During surgical intervention for the pathological femur fracture, an incisional biopsy was performed by meticulous curettage of the dysplastic tissue. The tissue samples were sent for histopathological examination. Which of the following histopathological findings would definitively confirm the diagnosis of fibrous dysplasia in this patient?

. Lobules of hyaline cartilage with increased cellularity and nuclear atypia.
. Blood-filled spaces separated by septa containing fibroblasts and osteoclast-like giant cells.
. Irregularly shaped trabeculae of immature woven bone without osteoblastic rimming, embedded in a loose fibrous stroma.
. Sheets of small round blue cells with high mitotic activity.
. Spindled cells with storiform pattern and pleomorphic nuclei.

Correct Answer & Explanation

. Irregularly shaped trabeculae of immature woven bone without osteoblastic rimming, embedded in a loose fibrous stroma.

Explanation

Correct Answer: CThe definitive histopathological hallmark of fibrous dysplasia is the presence of irregularly shaped trabeculae of immature woven bone, often described as having a 'Chinese characters' pattern, embedded within a loose, vascular fibrous stroma. Crucially, these woven bone trabeculae lack osteoblastic rimming, which differentiates them from normal or reactive bone formation. Option A describes features of a cartilaginous tumor, such as a chondrosarcoma. Option B describes the characteristic features of an aneurysmal bone cyst (ABC). Option D could describe Ewing sarcoma or lymphoma. Option E describes features often seen in pleomorphic sarcomas or malignant fibrous histiocytoma (now undifferentiated pleomorphic sarcoma). Therefore, option C is the specific and definitive histopathological finding for fibrous dysplasia.

Question 762

Topic: 10. Pathology and Oncology

A 45-year-old female presents with a similar expansile lytic lesion in her proximal femur, but her CT scan (similar to the example provided) shows focal cortical breakthrough, significant endosteal erosion exceeding 2/3 of cortical thickness, and characteristic 'rings and arcs' calcification within the lesion. Her biopsy reveals lobules of hyaline cartilage with increased cellularity and nuclear atypia.

Based on these described CT and histopathological findings, which alternative diagnosis should be most strongly considered, and what is its key differentiating feature from fibrous dysplasia?

. Aneurysmal Bone Cyst, characterized by fluid-fluid levels on MRI.
. Giant Cell Tumor, characterized by epiphyseal location and lack of matrix.
. Low-Grade Chondrosarcoma, characterized by chondroid matrix calcification and aggressive cortical involvement.
. Brown Tumor of Hyperparathyroidism, characterized by elevated PTH and generalized osteopenia.
. Non-ossifying Fibroma, characterized by sclerotic rim and metaphyseal location.

Correct Answer & Explanation

. Low-Grade Chondrosarcoma, characterized by chondroid matrix calcification and aggressive cortical involvement.

Explanation

Correct Answer: CThe described CT findings of 'focal cortical breakthrough, significant endosteal erosion exceeding 2/3 of cortical thickness, and characteristic 'rings and arcs' calcification within the lesion' are highly suggestive of a cartilaginous tumor. The 'rings and arcs' pattern is classic for chondroid matrix calcification. When combined with histopathology showing 'lobules of hyaline cartilage with increased cellularity and nuclear atypia,' this definitively points to a Low-Grade Chondrosarcoma (LGCS), also known as an Atypical Cartilaginous Tumor (ACT). Fibrous dysplasia, in contrast, typically shows a 'ground-glass' matrix and woven bone on histology, not chondroid calcification or atypical cartilage. While ABCs have fluid-fluid levels, GCTs are epiphyseal, brown tumors have metabolic derangements, and non-ossifying fibromas have a sclerotic rim, none of these fit the described imaging and pathological features as well as LGCS.

Question 763

Topic: 10. Pathology and Oncology

A 25-year-old patient with monostotic fibrous dysplasia of the femur undergoes intralesional curettage and intramedullary nailing for a pathological fracture. Two years later, he presents with new onset pain and radiographic evidence of lesion expansion at the previous surgical site. A repeat biopsy confirms recurrent fibrous dysplasia. Which of the following is the most likely reason for this patient's recurrence?

. Malignant transformation to osteosarcoma.
. Inadequate initial curettage of the dysplastic tissue.
. Failure to use an intramedullary nail for stabilization.
. Development of a secondary aneurysmal bone cyst.
. Progression of polyostotic fibrous dysplasia.

Correct Answer & Explanation

. Inadequate initial curettage of the dysplastic tissue.

Explanation

Correct Answer: BOne of the key pitfalls in the management of fibrous dysplasia, as highlighted in the case, is incomplete curettage. Fibrous dysplasia lesions, especially aggressive or expansile ones, have a high local recurrence rate if the dysplastic tissue is not thoroughly removed. Simple curettage without aggressive burring or augmentation (e.g., with PMMA) often leaves residual dysplastic cells, leading to recurrence. While malignant transformation (Option A) is a rare but serious complication, it would typically present with more aggressive radiographic changes and a different histopathology (e.g., osteosarcoma). Failure to use an intramedullary nail (Option C) would primarily lead to fixation failure or non-union, not necessarily recurrence of the lesion itself. Development of a secondary ABC (Option D) is possible but less likely to be the primary cause of recurrence if the underlying FD was not adequately addressed. Progression to polyostotic disease (Option E) is a different phenomenon, implying new lesions elsewhere, not recurrence at the original monostotic site.

Question 764

Topic: 10. Pathology and Oncology

Following successful surgical stabilization and rehabilitation, the patient is discharged with a confirmed diagnosis of monostotic fibrous dysplasia. Given the nature of this condition, what is the most appropriate long-term surveillance strategy for this patient?

. No further follow-up is required as the lesion is benign and treated.
. Annual clinical and radiographic review for several years, with further imaging for new symptoms.
. Bi-annual MRI scans for 5 years to rule out malignant transformation.
. Routine blood tests every 6 months to monitor for metabolic changes.
. Prophylactic radiation therapy to prevent recurrence.

Correct Answer & Explanation

. Annual clinical and radiographic review for several years, with further imaging for new symptoms.

Explanation

Correct Answer: BThe case emphasizes that patients with fibrous dysplasia require long-term surveillance due to the potential for disease progression, local recurrence, or, albeit rare (0.4-4%), malignant transformation (most commonly to osteosarcoma). Therefore, annual clinical and radiographic review for several years is advisable. Further imaging (e.g., CT or MRI) should be obtained if any new symptoms (pain, swelling, deformity) or suspicious findings on routine radiographs emerge. Option A is incorrect as surveillance is necessary. Option C (bi-annual MRI for 5 years) is overly aggressive and not standard for routine surveillance of a stable, treated monostotic lesion unless specific concerns arise. Option D (routine blood tests) is generally not indicated unless there are signs of metabolic derangement or suspicion of polyostotic disease with endocrine involvement. Option E (prophylactic radiation therapy) is contraindicated due to the known risk of inducing malignant transformation in fibrous dysplasia.

Question 765

Topic: Bone Tumors
The patient's initial systemic examination and laboratory investigations were unremarkable. Specifically, there was no café-au-lait pigmentation, and serum calcium, phosphate, and alkaline phosphatase levels were within normal ranges. The absence of these findings in this patient helps to rule out which of the following associated syndromes or conditions?
. Neurofibromatosis Type 1
. Ollier's disease
. McCune-Albright syndrome
. Maffucci syndrome
. Paget's disease of bone

Correct Answer & Explanation

. McCune-Albright syndrome

Explanation

McCune-Albright syndrome is a classic triad characterized by polyostotic fibrous dysplasia, café-au-lait skin pigmentation, and various endocrine dysfunctions (e.g., precocious puberty, hyperthyroidism, acromegaly, Cushing's syndrome). The absence of café-au-lait spots and normal endocrine labs effectively rules out McCune-Albright syndrome in this patient, confirming his monostotic presentation without systemic involvement. Neurofibromatosis Type 1 is associated with café-au-lait spots but typically presents with neurofibromas and other skeletal dysplasias, not fibrous dysplasia as its primary bone lesion. Ollier's disease and Maffucci syndrome are characterized by multiple enchondromas, not fibrous dysplasia. Paget's disease of bone is a metabolic bone disease of older adults, characterized by disorganized bone remodeling and typically elevated alkaline phosphatase, which was normal in this patient.

Question 766

Topic: 10. Pathology and Oncology
A 14-year-old female presents with multiple bony deformities, unilateral café-au-lait spots with irregular borders, and a history of precocious puberty. A biopsy of a femoral lesion demonstrates woven bone trabeculae in a fibrous stroma without osteoblastic rimming. The pathogenesis of her condition is most directly linked to a mutation affecting which of the following?
. FGF23 production leading to renal phosphate wasting
. Constitutive activation of the Gs-alpha protein and elevated cAMP
. Inactivating mutation of the EXT1 tumor suppressor gene
. Overexpression of RANKL leading to excessive osteoclast activity
. Defect in type I collagen synthesis

Correct Answer & Explanation

. Constitutive activation of the Gs-alpha protein and elevated cAMP

Explanation

This patient has McCune-Albright syndrome, a severe form of polyostotic fibrous dysplasia. It is caused by a post-zygotic activating mutation in the GNAS1 gene, which leads to constitutive activation of the Gs-alpha protein and elevated intracellular cAMP levels.

Question 767

Topic: Bone Tumors

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 reveals a well-circumscribed, lobulated intramuscular mass that is T1-hypointense and markedly T2-hyperintense with mild peripheral enhancement. What is the most likely diagnosis associated with this syndrome?

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

Correct Answer & Explanation

. Mazabraud syndrome

Explanation

Mazabraud syndrome is characterized by the association of fibrous dysplasia with single or multiple intramuscular myxomas. The MRI findings described are classic for an intramuscular myxoma.

Question 768

Topic: Bone Tumors

A 16-year-old male with fibrous dysplasia presents with increasing thigh pain and a progressive varus deformity of the proximal femur, characteristic of a 'Shepherd's crook' deformity. Non-operative management has failed. Which of the following is the most appropriate surgical management?

. Curettage and bone grafting alone
. Open reduction and internal fixation with a dynamic hip screw
. Varus-producing proximal femoral osteotomy with plate fixation
. Valgus-producing proximal femoral osteotomy and intramedullary nailing
. Resection and endoprosthetic reconstruction

Correct Answer & Explanation

. Valgus-producing proximal femoral osteotomy and intramedullary nailing

Explanation

Surgical management of a Shepherd's crook deformity requires a valgus-producing osteotomy to restore mechanical alignment, followed by fixation with a load-sharing intramedullary nail. Rigid plate fixation or cortical bone grafting alone has a high failure rate in fibrous dysplasia.

Question 769

Topic: Bone Tumors

A 12-year-old girl presents with precocious puberty, cafe-au-lait spots with irregular borders, and a newly discovered lytic lesion in her proximal femur resulting in a 'shepherd's crook' deformity. What is the underlying genetic and pathophysiologic mechanism of this patient's skeletal disease?

. Mutation in the EXT1 gene leading to abnormal heparan sulfate synthesis
. Activating mutation of the GNAS gene resulting in increased intracellular cAMP
. Inactivating mutation of the PTEN gene leading to overactive mTOR signaling
. Overproduction of FGF-23 causing renal phosphate wasting
. Defect in Type I collagen synthesis leading to brittle bones

Correct Answer & Explanation

. Activating mutation of the GNAS gene resulting in increased intracellular cAMP

Explanation

This patient has McCune-Albright syndrome, characterized by polyostotic fibrous dysplasia, precocious puberty, and cafe-au-lait spots. The underlying cause is a somatic activating mutation in the GNAS gene, which continuously activates Gs-alpha, leading to elevated intracellular cAMP levels.

Question 770

Topic: 10. Pathology and Oncology

A 45-year-old female with known polyostotic fibrous dysplasia presents with multiple painless soft tissue masses in her right thigh. Biopsy of one of the masses reveals an intramuscular myxoma. Which of the following syndromes does this patient possess?

. McCune-Albright Syndrome
. Jaffe-Campanacci Syndrome
. Mazabraud Syndrome
. Ollier Disease
. Maffucci Syndrome

Correct Answer & Explanation

. Mazabraud Syndrome

Explanation

Mazabraud syndrome is a rare condition characterized by the association of single or multiple intramuscular myxomas with monostotic or polyostotic fibrous dysplasia. The myxomas are typically benign and occur in the same anatomic region as the bone lesions.

Question 771

Topic: 10. Pathology and Oncology

A 22-year-old male with a symptomatic benign lytic lesion of the diaphyseal humerus undergoes an incisional biopsy. Histology shows irregular trabeculae of woven bone arranged in 'Chinese letter' patterns within a moderately cellular fibrous stroma, completely lacking osteoblastic rimming. What is the diagnosis?

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

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

The histologic hallmark of fibrous dysplasia is irregular, curvilinear trabeculae of woven bone (Chinese letters) in a fibrous stroma without osteoblastic rimming. Osteofibrous dysplasia, in contrast, typically demonstrates prominent osteoblastic rimming.

Question 772

Topic: Bone Tumors

A 12-year-old girl is diagnosed with polyostotic fibrous dysplasia and precocious puberty. What is the underlying molecular pathogenesis of her musculoskeletal condition?

. Activating mutation in GNAS gene causing decreased cAMP
. Activating mutation in GNAS gene causing increased cAMP
. Inactivating mutation in EXT1 gene
. Mutation in FGFR3 gene
. Mutation in COL1A1 gene

Correct Answer & Explanation

. Activating mutation in GNAS gene causing increased cAMP

Explanation

McCune-Albright syndrome involves a post-zygotic activating mutation in the GNAS gene, leading to continuous activation of the Gs alpha protein. This results in an overproduction of cAMP, driving the characteristic bone lesions and endocrinopathies.

Question 773

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. MRI reveals a well-circumscribed intramuscular mass with high T2 signal and low T1 signal. What is the most likely diagnosis of this soft tissue lesion?

. Liposarcoma
. Synovial sarcoma
. Intramuscular myxoma
. Neurofibroma
. Desmoid tumor

Correct Answer & Explanation

. Intramuscular myxoma

Explanation

The presence of fibrous dysplasia combined with intramuscular myxomas is the hallmark of Mazabraud syndrome. Intramuscular myxomas characteristically show low T1 and high T2 signal on MRI and are benign.

Question 774

Topic: Bone Tumors

A 30-year-old male requires surgical stabilization of a progressive "shepherd's crook" deformity of the proximal femur due to fibrous dysplasia. Which of the following principles is most critical for surgical success?

. Use of rigid plate osteosynthesis
. Prophylactic radiation therapy to prevent recurrence
. Use of intramedullary fixation and cortical bone strut allograft
. Use of intramedullary fixation and cancellous autograft
. Marginal wide resection of the affected bone

Correct Answer & Explanation

. Use of intramedullary fixation and cortical bone strut allograft

Explanation

In fibrous dysplasia, intramedullary fixation is preferred over plating to prevent peri-implant fractures. Cortical bone allograft is favored over cancellous bone, as the dysplastic process tends to rapidly resorb cancellous graft.

Question 775

Topic: Bone Tumors

A 14-year-old male with McCune-Albright syndrome presents with progressive lower extremity bowing and diffuse bone pain. Laboratory evaluation reveals hypophosphatemia, normal serum calcium, and elevated alkaline phosphatase. Which of the following mediators is most likely responsible for his metabolic bone abnormalities?

. Parathyroid hormone (PTH)
. Fibroblast growth factor 23 (FGF-23)
. 1,25-dihydroxyvitamin D
. Calcitonin
. Sclerostin

Correct Answer & Explanation

. Fibroblast growth factor 23 (FGF-23)

Explanation

Patients with fibrous dysplasia can develop hypophosphatemic rickets/osteomalacia due to the overproduction of FGF-23 by the dysplastic lesional tissue. FGF-23 causes renal phosphate wasting and decreases active vitamin D levels.

Question 776

Topic: Bone Tumors

A 32-year-old female with known polyostotic fibrous dysplasia presents with worsening right groin pain. Radiographs demonstrate a severe varus deformity of the proximal femur ("Shepherd's crook" deformity) with extensive cortical thinning, but no acute fracture is seen. What is the most appropriate surgical management?

. Extensive curettage and filling with structural allograft.
. Valgus-producing proximal femoral osteotomy stabilized with an intramedullary nail.
. Open reduction and internal fixation with a sliding hip screw device.
. Total hip arthroplasty with a diaphyseal-fitting stem.
. Observation and initiation of intravenous bisphosphonates.

Correct Answer & Explanation

. Valgus-producing proximal femoral osteotomy stabilized with an intramedullary nail.

Explanation

A Shepherd's crook deformity places severe biomechanical stress on the proximal femur, risking pathologic fracture. The preferred surgical treatment is a valgus-producing osteotomy to correct the mechanical axis, stabilized by an intramedullary nail to protect the entire length of the dysplastic femur.

Question 777

Topic: 10. Pathology and Oncology

A 22-year-old male undergoes a core needle biopsy of an expansile, radiolucent rib lesion found incidentally. The pathology report describes irregular, C-shaped woven bone trabeculae set within a moderately cellular fibrous stroma. Which of the following additional histologic features is classic for this diagnosis?

. Prominent osteoblastic rimming of the trabeculae.
. Lack of osteoblastic rimming around the bony trabeculae.
. Sheets of small round blue cells with interspersed rosettes.
. A "herringbone" architectural pattern of spindle cells.
. Abundant multinucleated giant cells with background hemorrhage.

Correct Answer & Explanation

. Lack of osteoblastic rimming around the bony trabeculae.

Explanation

The lesion described is fibrous dysplasia, which characteristically shows irregular woven bone trabeculae resembling "Chinese characters." A hallmark distinguishing feature of fibrous dysplasia is the lack of osteoblastic rimming around these woven bone trabeculae.

Question 778

Topic: 10. Pathology and Oncology

A 14-year-old male presents with a 5-month history of progressive left knee and distal thigh pain. Initially, the pain was intermittent and activity-related, but over the preceding eight weeks, it transitioned to constant, severe nocturnal pain that consistently awakened him from sleep and was refractory to over-the-counter medications. Concurrently, a slowly enlarging, firm, non-mobile soft tissue mass was noted on the anterior and lateral aspects of the distal left thigh. Which of the following clinical findings, if present, would be MOST concerning for a malignant etiology in this patient?

. Intermittent, dull pain related to high-impact activities.
. Transient symptomatic relief with rest and cryotherapy.
. Development of severe nocturnal pain awakening the patient from sleep.
. Absence of constitutional symptoms such as fever or weight loss.
. Mild disuse atrophy of the proximal quadriceps musculature.

Correct Answer & Explanation

. Development of severe nocturnal pain awakening the patient from sleep.

Explanation

Correct Answer: CThe case explicitly highlights that the transition of pain from activity-dependent to constant, severe nocturnal pain that awakens the patient from sleep is acritical clinical indicator of an aggressive, space-occupying intramedullary processcausing endosteal pressure and periosteal stretching. While the presence of a growing, firm mass is also highly concerning, the evolution of pain to include a severe nocturnal component is a classic red flag for primary malignant bone tumors in the pediatric and adolescent population. Options A and B describe the initial, less concerning symptoms that are often misattributed to benign causes. Option D, the absence of constitutional symptoms, is not a reliable indicator to rule out malignancy, as many sarcomas do not present with systemic symptoms. Option E, mild disuse atrophy, is a secondary effect of pain and functional limitation, not a primary indicator of malignancy itself.

Question 779

Topic: 10. Pathology and Oncology

During the physical examination of the 14-year-old male with a distal femoral mass, the orthopedic oncologist notes a prominent network of engorged superficial veins overlying the mass, increased local skin temperature, and a positive patellar tap test. Which of these findings, in isolation, is LEAST specific for a high-grade malignant bone tumor?

. Prominent, engorged superficial veins.
. Increased local skin temperature.
. Firm, unyielding mass fixed to underlying bone.
. Ill-defined superior margins of the mass blending into surrounding musculature.
. Positive patellar tap test.

Correct Answer & Explanation

. Positive patellar tap test.

Explanation

Correct Answer: EA positive patellar tap test indicates the presence of a knee joint effusion. While a reactive effusion can occur secondary to an adjacent malignant bone tumor (as noted in the case), it is a non-specific finding. Joint effusions can be caused by a wide range of conditions, including trauma, infection, inflammatory arthritis, and other benign processes. In contrast, prominent, engorged superficial veins (neoangiogenesis), increased local skin temperature (increased metabolic activity), a firm and unyielding mass fixed to bone, and ill-defined margins suggesting extraosseous extension are all highly characteristic clinical signs of an aggressive, rapidly growing malignant bone tumor like osteosarcoma.

Question 780

Topic: Bone Tumors

A 14-year-old male presents with progressive left knee pain and a distal femoral mass. Initial plain radiographs of the left distal femur are shown below.

Based on these images and the clinical presentation, which of the following radiographic features is MOST characteristic of the likely diagnosis?

. A purely lytic lesion with a narrow zone of transition.
. A 'soap bubble' appearance with internal septations.
. A prominent 'sunburst' periosteal reaction and Codman's triangle.
. A smooth, lamellated 'onion-skin' periosteal reaction.
. A well-defined sclerotic border with central lucency.

Correct Answer & Explanation

. A prominent 'sunburst' periosteal reaction and Codman's triangle.

Explanation

Correct Answer: CThe plain radiographs in the case description explicitly detail a 'prominent 'sunburst' or 'hair-on-end' periosteal reaction' and a 'distinct Codman's triangle' along with a mixed lytic and blastic appearance and cortical destruction. These features are classic radiographic hallmarks of osteosarcoma, indicating a rapidly aggressive tumor that is lifting the periosteum and producing new bone in a disorganized fashion. Options A and E describe features more typical of benign or less aggressive lesions (e.g., non-ossifying fibroma, fibrous dysplasia). Option B ('soap bubble' appearance) is characteristic of giant cell tumor or aneurysmal bone cyst. Option D ('onion-skin' periosteal reaction) is a classic feature of Ewing sarcoma, which typically presents with a permeative lytic pattern and is often diaphyseal or metadiaphyseal.

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