10. Pathology and Oncology MCQs

A 50-year-old female has a chronically swollen knee. MRI is obtained.

Which specific MRI sequence characteristic most definitively establishes the diagnosis of lipoma arborescens?

While lipoma arborescens is generally considered a benign, slow-growing neoplastic condition, it is most frequently encountered in patients with a history of which of the following underlying joint pathologies?

A 38-year-old female presents with a slowly enlarging, boggy right knee effusion. MRI reveals a large, villous synovial mass in the suprapatellar pouch.

To reliably differentiate lipoma arborescens from Pigmented Villonodular Synovitis (PVNS) on MRI, which of the following imaging characteristics is most uniquely diagnostic of lipoma arborescens?

A diabetic patient has a 2 cm plantar ulcer under the first metatarsal head. During clinical examination, a sterile blunt probe is introduced into the ulcer and touches hard, gritty bone. What is the most likely diagnosis based on this specific clinical finding?

A 14-year-old boy presents with a painful, enlarging mass on his right thigh 3 weeks after sustaining a minor femur fracture. Radiographs demonstrate exuberant bone formation that mimics osteosarcoma. Physical examination also reveals limited forearm pronation and supination. What is the most likely genetic mutation responsible for his underlying condition?

A 14-year-old boy presents with a painful, enlarging mass on his right femur following minor trauma 3 weeks ago. Radiographs demonstrate a massive, dense callus formation without signs of malignancy. Physical examination reveals limited forearm pronation and supination bilaterally, and his sclerae are white. Genetic testing for this patient is most likely to reveal a mutation in which of the following genes?

A 48-year-old male develops progressive lower extremity weakness and multiple insufficiency fractures. Laboratory workup reveals profound hypophosphatemia, normal calcium, normal parathyroid hormone, and inappropriately low 1,25-dihydroxyvitamin D. What is the pathophysiologic mechanism of this patient's condition?

A 62-year-old male presents with increasing pain and malodorous drainage from a chronic sinus tract in his tibia that has been present for 35 years following an open fracture. A recent biopsy of the tract reveals malignant cells. What is the most common histologic subtype of this malignancy?

A 50-year-old patient with end-stage renal disease undergoes a transiliac bone biopsy. The histomorphometric analysis demonstrates wide osteoid seams and an increased mineralization lag time.

Which of the following underlying mechanisms best explains this specific finding?

A 55-year-old man presents with generalized bone pain and profound muscle weakness. Laboratory studies reveal hypophosphatemia, normal serum calcium, elevated alkaline phosphatase, and elevated FGF-23 levels. What is the most likely etiology of his osteomalacia?

A 52-year-old man presents with diffuse bone pain and proximal muscle weakness. Laboratory studies show hypophosphatemia, normal serum calcium, normal PTH, and elevated FGF23. A small mesenchymal tumor is found in his thigh. Complete surgical excision of the tumor will most likely lead to which of the following?

A 45-year-old male presents with worsening lower extremity pain, muscle weakness, and multiple rib fractures. Laboratory studies reveal severe hypophosphatemia, normal calcium, elevated alkaline phosphatase, and low 1,25-dihydroxyvitamin D. PTH is normal. A PET scan reveals a small soft-tissue mass in the plantar aspect of his foot. Overproduction of which of the following substances by this tumor is responsible for his condition?

A 50-year-old male presents with profound muscle weakness and multiple pseudofractures. Laboratory studies show hypophosphatemia, normocalcemia, normal PTH, and inappropriately low 1,25-dihydroxyvitamin D. Which of the following is the most likely etiology?

To confirm a suspected diagnosis of osteomalacia and assess bone turnover dynamics, an undecalcified bone biopsy is obtained.

Which of the following labeling agents is administered prior to the biopsy to evaluate the mineralization apposition rate?

In a patient with CREST syndrome, which of the following represents the most widely accepted orthopedic indication for surgical excision of calcinosis cutis lesions?

A 14-year-old girl undergoes curettage of a 3.5 cm lytic bone lesion in the distal femur. The histology is shown.

Microscopy reveals loose fibrovascular connective tissue intermixed with irregular osteoid without atypical mitoses. Her pain was poorly relieved by NSAIDs. What is the diagnosis?

A 7-year-old boy presents with fever, swelling, and pain in the midshaft of his femur. Radiographs show a permeative diaphyseal lesion with an onion-skin periosteal reaction. Cytogenetics reveal a t(11;22) translocation. Which fusion gene is associated with this condition?

A 13-year-old boy presents with chronic knee pain. Radiographs show an eccentrically located, lytic epiphyseal lesion in the proximal tibia with a sclerotic margin. Biopsy shows mononuclear cells and chicken-wire calcifications. What is the diagnosis?