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10. Pathology and Oncology MCQs

Practice Set 10 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 181

Topic: 10. Pathology and Oncology

A 12-year-old boy presents with painless, hard, fixed masses near his distal radius and proximal tibia, along with progressive forearm bowing.

What is the most likely underlying genetic mechanism for his condition?

. Mutation in the FGFR3 gene
. Defect in type I collagen synthesis
. Mutation in the EXT1 or EXT2 genes
. Mutation in the COMP gene
. Mutation in the GNAS1 gene

Correct Answer & Explanation

. Mutation in the EXT1 or EXT2 genes

Explanation

The clinical picture describes Multiple Hereditary Exostoses (MHE), characterized by multiple osteochondromas. This condition is inherited in an autosomal dominant pattern and is associated with mutations in the EXT1 and EXT2 tumor suppressor genes.

Question 182

Topic: Bone Tumors
The radiograph (Slide 1) of an 11-year-old boy with significant leg pain is presented. No other abnormalities are found during the patient's history or physical examination. The most likely diagnosis is:
. Osteomyelitis
. Fibrous dysplasia
. Enchondroma
. Unicameral bone cyst
. Ewing sarcoma

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

Fibrous dysplasia is chronically expansile with vague transition to normal bone and a 'ground-glass' appearance. These characteristics differentiate fibrous dysplasia from aneurysmal and unicameral bone cysts. Additionally, the lack of periosteal reaction differentiates fibrous dysplasia from malignancy or osteomyelitis. The patient's magnetic resonance image (Slide 2) is also provided.

Question 183

Topic: Bone Tumors

A 10-year-old boy presents with thigh pain that is worse at night and relieved dramatically by ibuprofen. Radiographs demonstrate a small radiolucent nidus surrounded by dense reactive sclerosis in the proximal femur.

What is the preferred definitive treatment if symptoms are refractory to medical management?

. En bloc resection
. Chemotherapy
. Radiofrequency ablation
. Radiation therapy
. Curettage and bone grafting

Correct Answer & Explanation

. Radiofrequency ablation

Explanation

The presentation is classic for an osteoid osteoma. Radiofrequency ablation (RFA) is the minimally invasive treatment of choice for symptomatic lesions failing conservative management.

Question 184

Topic: Bone Tumors

A 9-year-old boy sustains a minor fall and presents with arm pain. Radiographs reveal a mildly displaced pathologic fracture through a central, radiolucent, well-circumscribed lesion in the proximal humerus with a "fallen leaf" sign. What is the most likely diagnosis?

. Aneurysmal bone cyst
. Unicameral bone cyst
. Non-ossifying fibroma
. Fibrous dysplasia
. Osteosarcoma

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

A unicameral (simple) bone cyst is centrally located in the metaphysis of long bones in children. The "fallen leaf" or "fallen fragment" sign is pathognomonic for a pathologic fracture through the cyst.

Question 185

Topic: Bone Tumors

A 9-year-old boy presents with shoulder pain after a minor fall. Radiographs reveal a centrally located, radiolucent metaphyseal lesion in the proximal humerus with a cortical fragment resting at the bottom of the cyst. What is the most likely diagnosis?

. Aneurysmal bone cyst
. Unicameral bone cyst
. Non-ossifying fibroma
. Osteosarcoma
. Chondroblastoma

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

The 'fallen leaf' or 'fallen fragment' sign is pathognomonic for a unicameral bone cyst (UBC). It occurs when a fractured cortical fragment drops into the fluid-filled cavity of the cyst.

Question 186

Topic: 10. Pathology and Oncology

The best way to diagnose dysplasia epiphysealis hemimelica, in addition to history and physical, is:

. Bone scan
. Ultrasound
. Biopsy
. Plain radiograph
. Bacterial culture

Correct Answer & Explanation

. Plain radiograph

Explanation

Dysplasia epiphysealis hemimelica, or Trevor disease, is an epiphyseal osteochondroma. The characteristic location, continuity with the epiphysis and alteration in growth of the epiphysis, is the most specific confirmation of the disease. Histology is less specific, as are bone scan and ultrasound.

Question 187

Topic: 10. Pathology and Oncology
A 1-year-old child requires evaluation of limb length inequality. The surgeon notices a disproportional increase in length, as well as width, of the ipsilateral upper and lower extremity. No other physical abnormalities are evident. Recommended treatment includes which of the following:
. Ultrasound periodically throughout childhood
. Brain magnetic resonance imaging (MRI)
. MRI of the affected extremities
. Spinal ultrasound
. Angiogram of the affected limbs

Correct Answer & Explanation

. Ultrasound periodically throughout childhood

Explanation

Idiopathic hemihypertrophy is associated with an increased incidence of intra-abdominal tumors such as Wilms' tumor and hepatoblastoma. Periodic screening by ultrasound throughout childhood is recommended.

Question 188

Topic: Bone Tumors

An 8-year-old girl fractures her right femur when starting a sprint. Based on her radiograph (Slide), which of the following is the most likely diagnosis:

. Unicameral bone cyst
. Aneurysmal bone cyst
. Osteogenic sarcoma
. Fibrous dysplasia
. Normal pre-existing bone

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

This patient has signs of a pre-existing fibrous dysplasia lesion, including a central expansion of the subtrochanteric region with a ground-glass (not lucent) appearance. She was diagnosed with fibrous dysplasia.

Question 189

Topic: Bone Tumors
The patient presented in the radiograph (Slide) has a slight, painless limp. Which of the following is the most likely diagnosis:
. Ollier disease
. Osteogenesis imperfecta
. Fibrous dysplasia
. Neurofibromatosis
. Fibrous cortical defects

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

This patient has multiple "ground-glass" lesions and one cystic lesion, as well as bowing in the subtrochanteric region. The patient was diagnosed with fibrous dysplasia.

Question 190

Topic: 10. Pathology and Oncology

A newborn has multiple rigid joint contractures, featureless limbs lacking normal skin creases, and internal rotation of the shoulders. Sensation is intact, and intellect appears normal. Muscle biopsy is likely to show which of the following?

. Dystrophin deficiency
. Fibro-fatty replacement of muscle fibers
. Inflammatory infiltrates
. Glycogen accumulation
. Normal muscle architecture with hypertrophic fibers

Correct Answer & Explanation

. Fibro-fatty replacement of muscle fibers

Explanation

Amyoplasia is the most common form of arthrogryposis multiplex congenita. It is characterized by severe joint contractures and the replacement of skeletal muscle with dense fibrous tissue and fat.

Question 191

Topic: 10. Pathology and Oncology

A 12-year-old boy presents with multiple painless bony bumps around his knees and ankles. Radiographs demonstrate multiple osteochondromas. Which gene mutation is responsible, and what is its normal cellular function?

. EXT1 gene, encoding a tumor suppressor protein
. EXT2 gene, causing abnormal type 2 collagen synthesis
. EXT1 gene, involved in heparan sulfate synthesis
. RUNX2 gene, involved in osteoblast differentiation
. FGFR3 gene, inhibiting chondrocyte proliferation

Correct Answer & Explanation

. EXT1 gene, involved in heparan sulfate synthesis

Explanation

Multiple Hereditary Exostoses is caused by mutations in the EXT1 or EXT2 genes, which encode glycosyltransferases involved in the synthesis of heparan sulfate. Loss of this function alters signaling pathways in the growth plate, leading to osteochondroma formation.

Question 192

Topic: 10. Pathology and Oncology

A 3-year-old girl is evaluated for asymmetric overgrowth of her right leg. She has a history of an abdominal wall defect at birth, neonatal hypoglycemia, and macroglossia. She should be routinely screened with ultrasound for which of the following?

. Neuroblastoma
. Wilms tumor
. Osteosarcoma
. Retinoblastoma
. Ewing sarcoma

Correct Answer & Explanation

. Wilms tumor

Explanation

Beckwith-Wiedemann syndrome is an overgrowth disorder characterized by hemihypertrophy, macroglossia, and omphalocele. Patients have a significantly increased risk of embryonal tumors, particularly Wilms tumor and hepatoblastoma, necessitating routine ultrasound screening.

Question 193

Topic: Bone Tumors

A 10-year-old child, who has no history of fever, trauma, or infection, presents with minimal pain and a Trendelenburg gait on the left (Slide). Which of the following is the most likely diagnosis:

. Aneurysmal bone cyst
. Chronic osteomyelitis
. Fibrous dysplasia
. Unicameral bone cyst
. Enchondroma

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

This patient has fibrous dysplasia. The diffuse nature of the changes over a long portion of the bone, which includes blurring and thinning of the cortex, are classic signs of the disorder.

Question 194

Topic: 10. Pathology and Oncology

An 8-year-old child presents with a mass on the posteromedial side of the popliteal fossa. The mass, which has been present for more than 1 month, is nontender and moderately soft. The knee examination is stable. No knee effusion is present, and the patient has no signs or symptoms of infection. Radiographs are normal. Which of the following is the next step to aid in diagnosis:

. Magnetic resonance imaging
. Bone scan
. C omputed tomography
. Transillumination
. Biopsy

Correct Answer & Explanation

. Transillumination

Explanation

This patient demonstrates the classic presentation of a popliteal cyst. Transillumination often confirms the diagnosis of popliteal cyst, thereby avoiding the use of advanced imaging.

Question 195

Topic: 10. Pathology and Oncology

A 4-year-old boy presents with frequent falls and difficulty climbing stairs. On examination, he exhibits pseudohypertrophy of the calves and a positive Gowers sign. Which of the following is the most definitive diagnostic test for this condition?

. Muscle biopsy showing grouped atrophy
. Creatine kinase (CK) levels
. Electromyography (EMG)
. Genetic testing for dystrophin gene mutation
. Sural nerve biopsy

Correct Answer & Explanation

. Genetic testing for dystrophin gene mutation

Explanation

Duchenne muscular dystrophy is an X-linked recessive disorder caused by a mutation in the dystrophin gene. Genetic testing is the gold standard and most definitive diagnostic test, largely replacing muscle biopsies.

Question 196

Topic: 10. Pathology and Oncology

A 16-year-old boy presents with slowly progressive proximal muscle weakness. Muscle biopsy reveals reduced, but not absent, levels of dystrophin. He is diagnosed with Becker muscular dystrophy (BMD). What is the genetic transmission pattern of this disease?

. Autosomal dominant
. Autosomal recessive
. X-linked dominant
. X-linked recessive
. Mitochondrial inheritance

Correct Answer & Explanation

. X-linked recessive

Explanation

Both Duchenne and Becker muscular dystrophies are X-linked recessive disorders caused by mutations in the dystrophin gene. In BMD, the mutation allows for the production of a partially functional, truncated dystrophin protein.

Question 197

Topic: Bone Tumors

The lesion shown in the radiograph (pic) most likely represents which of the following processes:

. Aneurysmal bone cyst
. Fibrous dysplasia
. Unicameral bone cyst
. Osteomyelitis
. Fibrous cortical defect

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

The lesion shown in the radiograph is a unicameral bone cyst. The diagnosis was confirmed by aspiration and the subsequent response, filling in after autogenous marrow (pic).An aneurysmal bone cyst is typically more septated and expansile in width, fibrous dysplasia has a more blurred zone of transition and ground-glass appearance, and a fibrous cortical defect is more eccentrically placed.

Question 198

Topic: 10. Pathology and Oncology

A clinical photograph (Slide 1) and radiographs (Slide 2) of a 13-year-old girl, who is neurologically normal, are presented. She does not report any pain. The most likely diagnosis is:

. Fibrous dysplasia
. Blue-rubber bleb nevus syndrome
. Idiopathic scoliosis
. Neurofibromatosis-1
. Klippel-Trenaunay syndrome

Correct Answer & Explanation

. Neurofibromatosis-1

Explanation

This patient has neurofibromatosis-1. She has a dystrophic scoliosis that is sharply angulated and involves only four vertebrae (Cobb levels T12-L3). The pedicles are thinned, and the endplates are scalloped. She also has subcutaneous neurofibromas.

Question 199

Topic: Bone Tumors
A 12-year-old patient with fibrous dysplasia has an increasing limp and progressive bowing in the intertrochanteric and subtrochanteric regions of his femur. Recommended treatment includes:
. Allograft strut graft in situ
. Plate fixation in situ
. Rod fixation in situ
. Valgus osteotomy with plate and/or rod
. Hip arthrodesis in straight position

Correct Answer & Explanation

. Valgus osteotomy with plate and/or rod

Explanation

The most important step in treating patients with fibrous dysplasia is to decrease the bending force on the patient's femur. A valgus osteotomy with a plate or a rod decreases the bending force on the patient's femur by decreasing the offset from the center of the patient's body mass. Allografting and plate or rod fixation in situ causes progressive bowing in the patient.

Question 200

Topic: Bone Tumors

Which of the following bones is the most common site for involvement with fibrous dysplasia:

. Phalanges of the hand
. Radius
. Ulna
. Humerus
. Femur

Correct Answer & Explanation

. Femur

Explanation

The femur and the tibia are the most common sites of fibrous dysplasia in the appendicular skeleton. Involvement of the humerus is also common. Fibrous dysplasia may also occur in the radius, ulna, and phalanges of the hand; it occurs less frequently in the femur, humerus, and pelvis.

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