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10. Pathology and Oncology MCQs

Practice Set 317 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 6321

Topic: 10. Pathology and Oncology

A 65-year-old man presents with a pathologic fracture of the proximal humerus. Workup reveals a solitary large, destructive lytic lesion. Biopsy confirms metastatic clear cell renal cell carcinoma. What is the most critical step prior to operative stabilization?

. Neoadjuvant chemotherapy
. Preoperative angiographic embolization
. Immediate postoperative radiotherapy
. Systemic bisphosphonate infusion
. Intra-lesional injection of denosumab

Correct Answer & Explanation

. Preoperative angiographic embolization

Explanation

Renal cell carcinoma and thyroid carcinoma bone metastases are highly vascular. Preoperative angiographic embolization 24-48 hours before surgery is critical to minimize life-threatening intraoperative blood loss.

Question 6322

Topic: 10. Pathology and Oncology

A 40-year-old man with a 10-year history of recurrent primary synovial chondromatosis of the hip presents with a sudden, rapid increase in pain and joint swelling. Imaging shows a large new soft tissue mass with 'ring and arc' calcifications invading the surrounding acetabulum. What is the most likely diagnosis?

. Osteosarcoma
. Synovial sarcoma
. Secondary chondrosarcoma
. Malignant fibrous histiocytoma
. Metastatic carcinoma

Correct Answer & Explanation

. Secondary chondrosarcoma

Explanation

Primary synovial chondromatosis carries a small but documented risk (1-5%) of malignant transformation into secondary chondrosarcoma. A sudden increase in symptoms, rapidly expanding soft tissue mass, and marrow invasion on MRI are highly suspicious for this complication.

Question 6323

Topic: 10. Pathology and Oncology

A 55-year-old woman with metastatic breast cancer presents with mild hip pain. Radiographs reveal a lytic lesion involving 75% of the cortex in the peritrochanteric region of the right femur. According to Mirels' criteria, what is her score and recommended treatment?

. Score 8; Non-operative management with bisphosphonates
. Score 9; Prophylactic internal fixation
. Score 10; Prophylactic internal fixation
. Score 11; Non-operative management with radiotherapy
. Score 12; Immediate amputation

Correct Answer & Explanation

. Score 10; Prophylactic internal fixation

Explanation

Mirels score calculation: Site (Peritrochanteric = 3), Nature (Lytic = 3), Size (>2/3 cortex = 3), Pain (Mild = 1). Total score = 10. A score of 9 or greater is an absolute indication for prophylactic internal fixation.

Question 6324

Topic: 10. Pathology and Oncology

A 62-year-old woman undergoes intramedullary nailing for a pathologic fracture of the femur secondary to metastatic follicular thyroid carcinoma. Following surgical stabilization and appropriate wound healing, what is the preferred adjuvant treatment to specifically address the remaining microscopic disease at the bone metastasis site?

. External beam radiation therapy
. Radioactive iodine (I-131) ablation
. Intravenous bisphosphonate therapy
. Anti-VEGF monoclonal antibodies
. High-dose methotrexate

Correct Answer & Explanation

. Radioactive iodine (I-131) ablation

Explanation

Differentiated thyroid cancers (follicular and papillary) are unique in that their bone metastases often retain the ability to concentrate iodine. Radioactive iodine (I-131) ablation is the preferred adjuvant treatment to target the metastatic deposits, improving both local control and survival.

Question 6325

Topic: 10. Pathology and Oncology

A 45-year-old male develops atraumatic rib fractures and profound muscle weakness. Laboratory testing reveals hypophosphatemia, hyperphosphaturia, and profoundly elevated levels of FGF-23. Whole-body functional imaging is most likely to identify which of the following?

. Parathyroid adenoma
. Renal cell carcinoma
. Phosphaturic mesenchymal tumor
. Osteosarcoma
. Multiple myeloma

Correct Answer & Explanation

. Phosphaturic mesenchymal tumor

Explanation

Tumor-induced osteomalacia is a paraneoplastic syndrome typically caused by a benign phosphaturic mesenchymal tumor secreting FGF-23. This causes renal phosphate wasting, leading to hypophosphatemia and osteomalacia.

Question 6326

Topic: 10. Pathology and Oncology

A 55-year-old male presents with severe diffuse bone pain, proximal muscle weakness, and multiple Looser zones on radiographs. Labs reveal marked hypophosphatemia, hyperphosphaturia, normal calcium, and elevated FGF23. If a causative neoplasm is identified, it is most likely to be which of the following?

. Multiple myeloma
. Renal cell carcinoma
. Phosphaturic mesenchymal tumor
. Osteosarcoma
. Parathyroid adenoma

Correct Answer & Explanation

. Phosphaturic mesenchymal tumor

Explanation

Tumor-induced osteomalacia (TIO) is a paraneoplastic syndrome typically caused by a benign phosphaturic mesenchymal tumor that secretes excessive FGF23. Complete resection of the tumor usually cures the osteomalacia.

Question 6327

Topic: 10. Pathology and Oncology

A 65-year-old female with a history of severe celiac disease complains of bilateral groin pain. Radiographs demonstrate transverse lucencies with sclerotic margins along the medial aspect of bilateral femoral necks. These lesions (Looser zones) represent which of the following?

. Avascular necrosis
. Brown tumors
. Inadequate mineralization of uncalcified osteoid
. Aggregations of woven bone in pagetic lesions
. Malignant transformation of bone

Correct Answer & Explanation

. Inadequate mineralization of uncalcified osteoid

Explanation

Looser zones (pseudofractures) are wide transverse lucencies that represent stress fractures repaired by inadequately mineralized osteoid. They classically occur on the compressive side of bones, such as the medial femoral neck, in patients with osteomalacia.

Question 6328

Topic: 10. Pathology and Oncology

A 45-year-old immigrant presents with chronic back pain, night sweats, and weight loss. MRI of the thoracic spine demonstrates destruction of the T8 and T9 vertebral bodies with a large paraspinal abscess, but relative preservation of the T8-T9 intervertebral disc. Which of the following is the most likely diagnosis?

. Pyogenic spondylodiscitis
. Multiple myeloma
. Tuberculous spondylitis
. Metastatic prostate cancer
. Brucellosis

Correct Answer & Explanation

. Tuberculous spondylitis

Explanation

Tuberculous spondylitis (Pott's disease) classically demonstrates anterior vertebral body destruction with relative preservation of the intervertebral disc spaces until late in the disease. Pyogenic infections, in contrast, typically destroy the disc early.

Question 6329

Topic: 10. Pathology and Oncology
A 50-year-old male presents with diffuse bone pain and recurrent metatarsal fractures. Labs show severe hypophosphatemia, normal calcium, and elevated FGF-23 levels. A whole-body DOTATATE PET/CT reveals a small soft-tissue mass in his thigh. What is the expected outcome following complete marginal excision of the mass?
. Persistent hypophosphatemia requiring lifelong supplementation
. Rapid normalization of serum phosphate and FGF-23 levels
. Increased risk of hypercalcemia
. Development of tertiary hyperparathyroidism
. Progression to multiple myeloma

Correct Answer & Explanation

. Rapid normalization of serum phosphate and FGF-23 levels

Explanation

Tumor-induced osteomalacia is a paraneoplastic syndrome caused by an FGF-23 secreting phosphaturic mesenchymal tumor. Complete surgical resection of the tumor typically cures the condition, leading to rapid normalization of phosphate and FGF-23.

Question 6330

Topic: 10. Pathology and Oncology

A 55-year-old man presents with diffuse bone pain and progressive muscle weakness. Labs show profoundly low serum phosphate, normal calcium, normal PTH, and elevated alkaline phosphatase. A whole-body MRI reveals a small soft tissue mass in his thigh. Excision of this mass will reverse his symptoms by decreasing levels of:

. Calcium
. FGF23
. 1,25-dihydroxyvitamin D
. Calcitonin
. Parathyroid hormone

Correct Answer & Explanation

. FGF23

Explanation

Oncogenic osteomalacia (tumor-induced osteomalacia) is typically caused by a phosphaturic mesenchymal tumor that secretes excessive FGF23. Elevated FGF23 causes renal phosphate wasting; excision of the tumor is curative.

Question 6331

Topic: Bone Tumors

A 14-year-old girl with a history of precocious puberty and large cafe-au-lait spots presents with a pathologic fracture of her proximal femur. Radiographs show a ground-glass lytic lesion with a shepherd's crook deformity. What is the underlying genetic mutation?

. GNAS1
. EXT1
. NF1
. FGFR3
. SH3BP2

Correct Answer & Explanation

. GNAS1

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, cafe-au-lait spots (with irregular 'coast of Maine' borders), and endocrine abnormalities. It is caused by a post-zygotic somatic activating mutation in the GNAS1 gene.

Question 6332

Topic: 10. Pathology and Oncology

A 45-year-old presents with progressive diffuse bone pain and muscle weakness. Labs show profound hypophosphatemia, hyperphosphaturia, normal calcium, and low 1,25-dihydroxyvitamin D. Parathyroid hormone levels are normal. What is the most likely underlying mechanism?

. Vitamin D receptor mutation
. Mutation in the PHEX gene
. Overproduction of FGF-23
. Deficient 1-alpha-hydroxylase
. Parathyroid adenoma

Correct Answer & Explanation

. Overproduction of FGF-23

Explanation

The clinical picture describes tumor-induced osteomalacia, typically caused by a phosphaturic mesenchymal tumor. These tumors secrete FGF-23, which promotes renal phosphate wasting and inhibits 1-alpha-hydroxylase, leading to low active Vitamin D levels.

Question 6333

Topic: 10. Pathology and Oncology

A 9-year-old boy from Connecticut presents with a massive, painless effusion of the right knee. He is afebrile and has no history of trauma. Aspiration reveals 45,000 WBC/mcL with 80% PMNs. What is the most appropriate initial diagnostic test for the suspected etiology?

. Synovial fluid PCR for Kingella
. Serum ELISA for Borrelia burgdorferi
. Synovial biopsy for AFB
. Acid-fast staining of synovial fluid
. Immediate arthroscopic lavage

Correct Answer & Explanation

. Serum ELISA for Borrelia burgdorferi

Explanation

A massive, relatively painless knee effusion in an afebrile child from an endemic area is highly suspicious for Lyme arthritis. The appropriate initial diagnostic step is two-tier serologic testing starting with an ELISA for Borrelia burgdorferi, followed by a Western blot if positive.

Question 6334

Topic: 10. Pathology and Oncology
A 45-year-old male presents with severe diffuse bone pain, proximal muscle weakness, and multiple metatarsal stress fractures. Laboratory results show severe hypophosphatemia, normal serum calcium, normal PTH, and markedly elevated FGF-23 levels. What is the most appropriate next step in the workup of this patient?
. Initiate high-dose Vitamin D and calcium
. Whole-body DOTATATE PET/CT scan
. Four-gland parathyroid exploration
. Genetic testing for a PHEX mutation
. Intravenous bisphosphonate therapy

Correct Answer & Explanation

. Whole-body DOTATATE PET/CT scan

Explanation

This patient's presentation of adult-onset hypophosphatemia with elevated FGF-23 strongly suggests tumor-induced osteomalacia (TIO). A DOTATATE PET/CT or Octreoscan is the most appropriate step to locate the benign phosphaturic mesenchymal tumor responsible for the condition.

Question 6335

Topic: 10. Pathology and Oncology

A 15-year-old female presents with a painful, expansile, eccentric lytic lesion in the distal femoral metaphysis. Biopsy reveals blood-filled spaces lacking an endothelial lining. Which of the following genetic translocations is most specific to this primary lesion?

. t(11;22)
. t(X;18)
. t(16;17)
. t(9;22)
. t(2;13)

Correct Answer & Explanation

. t(16;17)

Explanation

Primary aneurysmal bone cysts (ABCs) are characterized by the t(16;17) translocation involving the CDH11 and USP6 genes. The USP6 upregulation drives the inflammatory and osteolytic nature of the tumor.

Question 6336

Topic: Bone Tumors

Which of the following magnetic resonance imaging (MRI) findings is most characteristic of an aneurysmal bone cyst?

. A uniform target sign on T2-weighted images
. Fluid-fluid levels on T2-weighted images
. A radiolucent nidus with surrounding dense sclerosis
. Popcorn calcification in the medullary canal
. A uniform ground-glass appearance

Correct Answer & Explanation

. Fluid-fluid levels on T2-weighted images

Explanation

Fluid-fluid levels on T2-weighted MRI are the hallmark of an aneurysmal bone cyst. This phenomenon occurs due to the separation of serum and red blood cells within the cystic spaces.

Question 6337

Topic: Bone Tumors
An 8-year-old female is evaluated for multiple bony deformities, irregular café-au-lait spots, and early onset of menses. Which of the following gene mutations is responsible for her condition?
. NF1
. COL1A1
. GNAS1
. EXT1
. FGFR3

Correct Answer & Explanation

. GNAS1

Explanation

This patient has McCune-Albright syndrome, a polyostotic form of fibrous dysplasia associated with endocrine abnormalities and coast of Maine café-au-lait spots. It is caused by an activating post-zygotic mutation in the GNAS1 gene, increasing cAMP levels.

Question 6338

Topic: Bone Tumors

A 25-year-old with polyostotic fibrous dysplasia undergoes surgical correction of a shepherd's crook deformity. If bone grafting is necessary, which of the following materials is relatively contraindicated due to its tendency to be rapidly resorbed?

. Cancellous autograft
. Cortical allograft
. Vascularized fibular graft
. Structural allograft strut
. Synthetic calcium phosphate

Correct Answer & Explanation

. Cortical allograft

Explanation

Cancellous autograft is contraindicated in fibrous dysplasia because it is rapidly resorbed and replaced by dysplastic host tissue. Cortical allograft is preferred as it undergoes slow creeping substitution, providing prolonged structural support.

Question 6339

Topic: Bone Tumors

When planning surgical fixation for an impending proximal femur fracture in a patient with a shepherd's crook deformity from fibrous dysplasia, which of the following implants provides the most reliable long-term outcome?

. Dynamic hip screw with a side plate
. Cephalomedullary nail
. Proximal femoral locking plate
. External fixator
. Hemiarthroplasty

Correct Answer & Explanation

. Cephalomedullary nail

Explanation

Intramedullary devices, such as a cephalomedullary nail, are the implants of choice for fibrous dysplasia in the lower extremity. Plates and screws have an unacceptably high failure rate due to poor screw purchase in the dysplastic bone.

Question 6340

Topic: 10. Pathology and Oncology

Secondary aneurysmal bone cysts are most commonly found arising within which of the following pre-existing benign bone tumors?

. Osteochondroma
. Giant cell tumor of bone
. Non-ossifying fibroma
. Osteoid osteoma
. Enchondroma

Correct Answer & Explanation

. Giant cell tumor of bone

Explanation

Secondary ABCs occur in up to 30% of cases and most commonly arise in association with a Giant Cell Tumor of bone. They can also be seen with chondroblastomas and osteoblastomas.

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