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10. Pathology and Oncology MCQs

Practice Set 13 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 241

Topic: Bone Tumors

In a 15-year-old patient with progressive Shepherd's crook deformity of the proximal femur due to fibrous dysplasia, what is the biomechanically preferred method of surgical stabilization?

. Curettage, cancellous autografting, and plate fixation
. Valgus osteotomy and intramedullary nailing
. External fixation
. Isolated curettage and cementation
. Observation and long-leg bracing

Correct Answer & Explanation

. Valgus osteotomy and intramedullary nailing

Explanation

Valgus osteotomy corrects the deformity, while intramedullary nailing provides a load-sharing construct spanning the entire bone length. Plating (load-bearing) frequently fails in the weak dysplastic bone.

Question 242

Topic: Bone Tumors

Aside from precocious puberty, which of the following endocrinopathies is most frequently seen in patients with McCune-Albright syndrome?

. Hypoparathyroidism
. Hyperthyroidism
. Type 1 Diabetes Mellitus
. Addison's disease
. Pheochromocytoma

Correct Answer & Explanation

. Hyperthyroidism

Explanation

Hyperthyroidism is the second most common endocrine abnormality in McCune-Albright syndrome. Others include Cushing's syndrome, acromegaly, and hypophosphatemic rickets.

Question 243

Topic: 10. Pathology and Oncology

A radiograph

of a 30-year-old male with long-standing fibrous dysplasia shows new cortical destruction and a soft tissue mass at the site of a previously stable lesion. He received localized therapeutic radiation in childhood. What is the most likely diagnosis?

. Pathologic fracture
. Aneurysmal bone cyst transformation
. Malignant transformation to osteosarcoma
. Osteomyelitis
. Benign progression of the fibrous dysplasia

Correct Answer & Explanation

. Malignant transformation to osteosarcoma

Explanation

Malignant transformation in fibrous dysplasia is rare (<1%) but risk is markedly increased by prior radiation exposure. Osteosarcoma and fibrosarcoma are the most common secondary malignancies.

Question 244

Topic: Bone Tumors
The cutaneous lesions associated with McCune-Albright syndrome can be clinically differentiated from those seen in Neurofibromatosis type 1 by which of the following characteristics?
. They are uniformly elevated and palpable.
. They frequently cross the midline of the body.
. They have irregular, jagged borders.
. They primarily affect the palms and soles.
. They fade completely following puberty.

Correct Answer & Explanation

. They have irregular, jagged borders.

Explanation

The café-au-lait macules in McCune-Albright syndrome typically have irregular, jagged borders ('Coast of Maine') and often respect the midline, whereas those in NF1 have smooth ('Coast of California') borders.

Question 245

Topic: Bone Tumors
In which of the following molecules is McCune-Albright syndrome due to a mutation?
. Fibroblast growth factor receptor protein
. GNAS1
. Bone morphogenetic protein
. Fibrillin
. Collagen type 1

Correct Answer & Explanation

. GNAS1

Explanation

McCune-Albright syndrome (also known as polyostotic fibrous dysplasia) is due to a mutation in GNAS1. GNAS1 is the alpha subunit of GS, which is a protein that links receptors to adenyl cyclase activity.

Question 246

Topic: Bone Tumors

Dysplasia epiphysialis hemimelia (Trevor disease) is a rare developmental disorder of the epiphysis. Histologically, the lesions of Trevor disease most closely resemble which of the following?

. Osteoid osteoma
. Osteochondroma
. Chondroblastoma
. Enchondroma
. Osteosarcoma

Correct Answer & Explanation

. Osteochondroma

Explanation

Trevor disease is characterized by asymmetric epiphyseal cartilage overgrowth. Histologically, it is identical to an osteochondroma, displaying a hyaline cartilage cap with underlying enchondral ossification.

Question 247

Topic: Bone Tumors
Which of the following conditions is represented in this radiograph of a child's neck?
. Osteoid osteoma of C1
. Jefferson's fracture
. Rotatory subluxation
. Hangman fracture
. Os odontoideum

Correct Answer & Explanation

. Rotatory subluxation

Explanation

This radiograph indicates a rotatory subluxation of a child's neck. Alteration of the cortical ring of the anterior atlas is present and superimposed on the lateral mass of atlas. Increased distance between the anterior atlas and axis is the result of rotation.

Question 248

Topic: Bone Tumors
The lesion indicated in this computed tomography most likely represents:
. Brodie's abscess
. Eosinophilic granuloma
. Osteosarcoma
. Osteoid osteoma
. Osteoma

Correct Answer & Explanation

. Osteoid osteoma

Explanation

This patient has an osteoid osteoma with pain in the lumbar spine where the lesion is located. The patient's osteoid osteoma shows hot on a photon emission computed tomography scan and is relieved by nonsteroidal anti-inflammatory agents. Most patients with osteoid osteoma with lesions have them in the posterior region of their vertebrae.

Question 249

Topic: Bone Tumors
In which pattern does the most common presentation of Trevor's disease occur:
. Generalized involvement of all extremities
. Distal medial areas of one lower extremity
. Proximal lateral areas of both lower extremities
. Distal medial areas of both upper extremities
. Proximal lateral areas of one upper extremity

Correct Answer & Explanation

. Distal medial areas of one lower extremity

Explanation

Trevor's disease, also known as dysplasia epiphysialis hemimelia, refers to epiphyseal osteochondromas. Epiphyseal osteochondromas are usually few in number and are more common on the distal and medial portions of the epiphysis of one lower extremity.

Question 250

Topic: Bone Tumors
Epiphyseal osteochondroma is also known as:
. Maffucci's syndrome
. Freiberg's fracture
. Larsen-Johansson disease
. Trevor's disease
. Iselin's disease

Correct Answer & Explanation

. Trevor's disease

Explanation

Epiphyseal osteochondroma is also known as Trevor's disease. Epiphyseal osteochondroma is localized to a specific region of the body, unlike multiple osteochondroma, which affects the entire body. Epiphyseal osteochondroma and multiple osteochondroma are unrelated disorders.

Question 251

Topic: 10. Pathology and Oncology
Which of the following conditions requires an ultrasound of the abdomen?
. Russell-Silver syndrome
. Camurati-Engelmann disease
. Idiopathic hemihypertrophy
. Congenital constriction band syndrome
. Blue rubber bleb nevus syndrome

Correct Answer & Explanation

. Idiopathic hemihypertrophy

Explanation

An ultrasound of the abdomen is indicated for patients with idiopathic hemihypertrophy to determine the development of Wilms tumor. Children with idiopathic hemihypertrophy have an increased incidence of Wilms' tumor. Children require periodic monitoring, and they should have an abdominal ultrasound 2 to 3 times per year until 8 years of age.

Question 252

Topic: 10. Pathology and Oncology

How often should patients with hemihypertrophy have an abdominal ultrasound:

. Once at 2 years old
. Yearly until 5 years old
. Two to three times per year until 8 years old
. Quarterly until 18 years old
. Yearly until 18 years old

Correct Answer & Explanation

. Two to three times per year until 8 years old

Explanation

Patients with idiopathic hemihypertrophy require periodic monitoring to determine the risk of Wilms tumor. The best method to monitor patients with idiopathic hemihypertrophy is a renal ultrasound two to three times per year until the patient is 8 years of age.

Question 253

Topic: 10. Pathology and Oncology
This patient has numerous (> 6) café au lait spots. The most likely diagnosis is:
. Fibrous dysplasia
. Osteofibrous dysplasia
. Neurofibromatosis 1
. Mazabraud's syndrome
. Osteogenesis imperfecta

Correct Answer & Explanation

. Neurofibromatosis 1

Explanation

Neurofibromatosis is an autosomal dominant condition that occurs in a peripheral and central form. The peripheral type is more common and called neurofibromatosis 1 (NF1). The central type is characterized by bilateral acoustic neurofibromatosis (NF2). The clinical presentation is variable. Patients may either have a severe form of NF1 with hundreds of neurofibromas in the skin or they may have only café au lait spots and deep neurofibromas that are easily apparent. Demographics of NF1 include: 1. Autosomal dominant with high degree of penetrance 2. Chromosomal abnormality - 17, NF1 gene (encodes neurofibromin) 3. Diagnostic criteria - two or more of the following: Six or more café au lait spots, two or more neurofibromas of any type or one plexiform neurofibroma, freckling in the axillary or inguinal area, optic glioma, two or more Lisch nodules, bone lesion, first-degree relative with NF1.

Question 254

Topic: Soft Tissue Tumors & Metastasis
This patient has numerous (> 6) café au lait spots. Which of the following describes the correct inheritance pattern?
. Autosomal recessive
. Autosomal dominant with low degree of penetrance
. Autosomal dominant with high degree of penetrance
. X-linked recessive
. X-linked dominant

Correct Answer & Explanation

. Autosomal dominant with high degree of penetrance

Explanation

Neurofibromatosis is an autosomal dominant condition that occurs in a peripheral and central form. The peripheral type is more common and called neurofibromatosis 1 (NF1). The central type is characterized by bilateral acoustic neurofibromatosis (NF2). The clinical presentation is variable. Patients may either have a severe form of NF1 with hundreds of neurofibromas in the skin or they may have only café au lait spots and deep neurofibromas that are easily apparent. Demographics of NF1 include: 1. Autosomal dominant with high degree of penetrance 2. Chromosomal abnormality - 17, NF1 gene (encodes neurofibromin) 3. Diagnostic criteria - two or more of the following: Six or more café au lait spots, two or more neurofibromas of any type or one plexiform neurofibroma, freckling in the axillary or inguinal area, optic glioma, two or more Lisch nodules, bone lesion, first-degree relative with NF1.

Question 255

Topic: 10. Pathology and Oncology

A researcher aims to amplify a specific sequence of DNA obtained from a giant cell tumor. Which of the following represents the correct sequence of thermal steps in a Polymerase Chain Reaction (PCR)?

. Annealing, Extension, Denaturation
. Denaturation, Annealing, Extension
. Extension, Denaturation, Annealing
. Denaturation, Extension, Annealing

Correct Answer & Explanation

. Denaturation, Annealing, Extension

Explanation

PCR cycles begin with denaturation of double-stranded DNA at high temperature (~94-98°C). This is followed by annealing of primers at a lower temperature, and finally extension by Taq polymerase.

Question 256

Topic: 10. Pathology and Oncology

The "bystander effect" in gene therapy, particularly relevant in orthopedic oncology and suicide gene strategies, refers to:

. The death of genetically unmodified tumor cells adjacent to genetically modified tumor cells
. The systemic immune response triggered by a viral vector
. The unexpected modification of host germline cells
. The neutralization of viral vectors by circulating host antibodies

Correct Answer & Explanation

. The death of genetically unmodified tumor cells adjacent to genetically modified tumor cells

Explanation

The bystander effect occurs when the therapeutic product (e.g., a toxic metabolite activated by a suicide gene) is transferred from transduced cells to neighboring untransduced tumor cells. This amplifies the tumoricidal effect.

Question 257

Topic: 10. Pathology and Oncology

An oncology researcher uses small interfering RNA (siRNA) to target mutant oncogenes in an osteosarcoma cell line. What is the expected mechanism of action of this targeted therapy?

. Upregulation of competitive tumor suppressor genes
. Direct binding and structural inhibition of mutant proteins
. Alteration of the host DNA sequence to correct the mutation
. Post-transcriptional gene silencing via mRNA degradation
. Prevention of retroviral vector integration into the genome

Correct Answer & Explanation

. Post-transcriptional gene silencing via mRNA degradation

Explanation

siRNA utilizes the RNA interference (RNAi) pathway to achieve post-transcriptional gene silencing. It binds to complementary mRNA transcripts, leading to their degradation and preventing protein translation.

Question 258

Topic: 10. Pathology and Oncology
A 7-year-old gymnast complains of pain in her medial midfoot. Radiographs reveal that the navicular is narrower and more sclerotic on this side than the other. The midfoot appears somewhat flattened. Your next step is to recommend:
. Open biopsy
. Electrical stimulation
. Percutaneous drilling
. Intravenous pamidronate
. Observation with rest as needed

Correct Answer & Explanation

. Observation with rest as needed

Explanation

The condition described best resembles Kohler's disease, or avascular necrosis of the tarsal navicular. This disease has a natural history of spontaneous improvement with time, and biopsy is not needed. Rest improves symptoms, although it is probably not mandatory. Sometimes with severe pain, a cast may help to speed improvement of symptoms.

Question 259

Topic: Bone Tumors
An 18-year-old man has chronic pain in his right thigh, which is foreshortened with an increased anterior bow. What is the most likely diagnosis?
. Chronic osteomyelitis
. Osteogenesis imperfecta
. Paget's disease
. Multiple enchondromas
. Fibrous dysplasia

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

This patient has polyostotic fibrous dysplasia. The diffuse enlargement in width is atypical for osteogenesis imperfecta or infection. Paget's disease is associated with increased sclerosis. Enchondromas produce more localized changes in the bones than fibrous dysplasia.

Question 260

Topic: Bone Tumors

A 12-year-old boy presents with night pain in his proximal tibia that is relieved by NSAIDs. Radiographs show a sclerotic lesion with a 1 cm radiolucent nidus. What is the most likely diagnosis?

. Osteoblastoma
. Osteosarcoma
. Osteoid osteoma
. Brodie's abscess
. Chondroblastoma

Correct Answer & Explanation

. Osteoid osteoma

Explanation

Night pain relieved by NSAIDs and a radiolucent nidus <1.5 cm surrounded by reactive sclerosis are pathognomonic for osteoid osteoma.

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