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10. Pathology and Oncology MCQs

Practice Set 251 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 5001

Topic: 10. Pathology and Oncology

Which molecular technique is most definitive for identifying the specific EWSR1-FLI1 fusion transcript in Ewing's Sarcoma?

. Western Blot
. Southern Blot
. Reverse Transcription Polymerase Chain Reaction (RT-PCR)
. Karyotyping
. Immunohistochemistry for CD99

Correct Answer & Explanation

. Reverse Transcription Polymerase Chain Reaction (RT-PCR)

Explanation

Reverse Transcription Polymerase Chain Reaction (RT-PCR) is the most definitive molecular technique for identifying the specific EWSR1-FLI1 fusion transcript by detecting the messenger RNA (mRNA) produced from the fused gene. FISH detects the chromosomal rearrangement, but RT-PCR confirms the functional transcript. Western blot detects protein. Southern blot detects DNA fragments. Karyotyping detects large chromosomal abnormalities but may miss cryptic translocations. Immunohistochemistry for CD99 detects the protein product but is not specific for the fusion transcript.

Question 5002

Topic: 10. Pathology and Oncology

The main reason for using proton therapy over conventional photon radiation in certain cases of Ewing's Sarcoma is:

. Proton therapy has a shorter treatment duration.
. Proton therapy causes less acute skin toxicity.
. Proton therapy allows for superior dose conformity, sparing normal tissues and reducing integral dose to the patient.
. Proton therapy is effective for treating metastatic disease.
. Proton therapy is less expensive than photon therapy.

Correct Answer & Explanation

. Proton therapy allows for superior dose conformity, sparing normal tissues and reducing integral dose to the patient.

Explanation

Proton therapy offers superior dose conformity compared to conventional photon radiation (X-rays). Protons deposit most of their energy at a specific depth (Bragg peak) and then stop, leading to minimal 'exit dose' beyond the target. This property allows for better sparing of surrounding healthy tissues and organs at risk, reducing late toxicities (e.g., secondary malignancies, growth abnormalities, organ damage), which is particularly beneficial for pediatric patients and tumors located near critical structures (e.g., spine, pelvis, skull base). It does not inherently have a shorter duration, cause less acute skin toxicity (though it can reduce chronic toxicity), or treat metastatic disease (it's local therapy). It is generally more expensive.

Question 5003

Topic: 10. Pathology and Oncology

What is the primary mechanism of action of the EWSR1-FLI1 fusion protein in Ewing's Sarcoma pathogenesis?

. It acts as a tumor suppressor gene, preventing cell division.
. It promotes DNA repair mechanisms, leading to drug resistance.
. It functions as an aberrant transcription factor, dysregulating gene expression critical for cell proliferation and survival.
. It causes direct degradation of cellular organelles, inducing apoptosis.
. It forms a structural component of the extracellular matrix, stiffening the tumor.

Correct Answer & Explanation

. It functions as an aberrant transcription factor, dysregulating gene expression critical for cell proliferation and survival.

Explanation

The EWSR1-FLI1 fusion protein acts as an aberrant chimeric transcription factor. The EWSR1 portion contributes a strong transcriptional activation domain, while the FLI1 portion provides DNA binding specificity. This fusion protein then aberrantly activates or represses genes involved in cell growth, differentiation, and survival, driving the oncogenic process. It is not a tumor suppressor, nor does it primarily promote DNA repair, cause organelle degradation, or form extracellular matrix components.

Question 5004

Topic: 10. Pathology and Oncology

Histopathologically, which feature, if present, would raise concern for a telangiectatic osteosarcoma rather than a benign Aneurysmal Bone Cyst, even in the presence of fluid-fluid levels on MRI?

. Numerous multinucleated giant cells.
. Hemosiderin deposition.
. Fibrous septa containing fibroblasts.
. Areas of frank osteoid production by malignant-appearing cells.
. Blood-filled spaces without endothelial lining.

Correct Answer & Explanation

. Areas of frank osteoid production by malignant-appearing cells.

Explanation

The definitive distinction between Aneurysmal Bone Cyst and telangiectatic osteosarcoma, especially challenging given their similar imaging features (fluid-fluid levels), relies heavily on identifying malignant-appearing osteoid produced by sarcomatous cells in telangiectatic osteosarcoma. While both can have giant cells, hemosiderin, and blood-filled spaces, the presence of frank osteoid production by atypical, pleomorphic cells is pathognomonic for osteosarcoma and indicates malignancy.

Question 5005

Topic: Bone Tumors

Which age group is most commonly affected by Aneurysmal Bone Cysts?

. Infants (0-1 year)
. Children and adolescents (5-20 years)
. Young adults (20-40 years)
. Middle-aged adults (40-60 years)
. Elderly (>60 years)

Correct Answer & Explanation

. Children and adolescents (5-20 years)

Explanation

Aneurysmal Bone Cysts primarily affect children and adolescents, with the vast majority of cases occurring between the ages of 5 and 20 years. They are rare in individuals over 30 and almost unheard of in the elderly. This age demographic is an important distinguishing factor from other lesions like Giant Cell Tumors, which typically affect skeletally mature young adults.

Question 5006

Topic: 10. Pathology and Oncology

A 9-year-old child presents with a painful, rapidly enlarging lesion in the tibia. X-rays show a lytic, expansile lesion. MRI shows multiple fluid-fluid levels. Given the rapid expansion and potential for local destruction, which description best characterizes the biological behavior of an Aneurysmal Bone Cyst?

. Benign, self-limiting lesion.
. Slow-growing, non-aggressive tumor.
. Benign, locally aggressive lesion.
. Malignant tumor with metastatic potential.
. Pre-malignant lesion with high risk of transformation.

Correct Answer & Explanation

. Benign, locally aggressive lesion.

Explanation

Aneurysmal Bone Cyst is correctly described as a benign, locally aggressive lesion. While benign, it can cause significant local destruction, rapid expansion, and can compromise adjacent neurovascular structures or growth plates. It is not self-limiting, nor is it a malignant tumor with metastatic potential or a pre-malignant lesion.

Question 5007

Topic: Bone Tumors

Which imaging modality is most sensitive for demonstrating the characteristic 'fluid-fluid levels' within an Aneurysmal Bone Cyst?

. Plain Radiography
. Computed Tomography (CT)
. Magnetic Resonance Imaging (MRI)
. Ultrasound
. Bone Scintigraphy

Correct Answer & Explanation

. Magnetic Resonance Imaging (MRI)

Explanation

Magnetic Resonance Imaging (MRI) is the imaging modality of choice for demonstrating fluid-fluid levels, which are highly characteristic of Aneurysmal Bone Cysts (ABCs). These levels represent sedimentation of blood products (serum, red blood cells, fibrin) within the cystic cavities. While CT can sometimes show them, MRI is far more sensitive and also provides excellent soft tissue detail for evaluating lesion extension.

Question 5008

Topic: 10. Pathology and Oncology

A 14-year-old patient with an Aneurysmal Bone Cyst in the distal radius has undergone curettage and cryotherapy. What is the most common complication following surgical treatment of ABCs?

. Malignant transformation.
. Development of a secondary infection.
. Local recurrence.
. Pathological fracture in a different bone.
. Anaphylaxis to anesthetic agents.

Correct Answer & Explanation

. Local recurrence.

Explanation

Despite aggressive treatment with curettage and adjuvant therapy, local recurrence is the most common complication following surgical treatment of Aneurysmal Bone Cysts. Recurrence rates vary depending on the location, size, and aggressiveness of the initial treatment, but can range from 10-30%. Malignant transformation is exceedingly rare. Secondary infection is possible but less common than recurrence. Pathological fracture in a different bone is not a complication of the treated ABC.

Question 5009

Topic: Bone Tumors

When distinguishing a primary Aneurysmal Bone Cyst from a Unicameral Bone Cyst (UBC), which feature is more typical of a primary ABC?

. Centrally located in the metaphysis.
. More common in patients over 20 years old.
. Fluid-fluid levels on MRI.
. Asymptomatic until pathological fracture.
. Response to intralesional corticosteroid injection.

Correct Answer & Explanation

. Fluid-fluid levels on MRI.

Explanation

Fluid-fluid levels on MRI are a hallmark feature of Aneurysmal Bone Cysts, reflecting the presence of blood and serum within the cystic cavities. UBCs are typically centrally located within the metaphysis, often asymptomatic until a pathological fracture, and can respond to intralesional corticosteroid injection (though efficacy is variable). ABCs are typically eccentric, more likely symptomatic with pain and swelling, and primarily affect children/adolescents.

Question 5010

Topic: Bone Tumors

Which of the following locations for an Aneurysmal Bone Cyst is most challenging to treat surgically and often requires consideration of alternative or multi-modal therapies?

. Distal radius
. Proximal tibia
. Lumbar vertebral body
. Femoral diaphysis
. Phalanges of the hand

Correct Answer & Explanation

. Lumbar vertebral body

Explanation

Aneurysmal Bone Cysts in the axial skeleton, particularly the sacrum and vertebral bodies (like the lumbar vertebral body in this option), are notoriously challenging to treat surgically due to their deep location, proximity to vital neurovascular structures, and often high vascularity. These locations frequently require pre-operative embolization, careful surgical planning, and sometimes less aggressive intralesional approaches or even non-surgical management. Long bones and appendicular skeleton locations are generally more accessible.

Question 5011

Topic: Bone Tumors

What is the role of preoperative selective arterial embolization in the management of large Aneurysmal Bone Cysts?

. To definitively cure the lesion without subsequent surgery.
. To confirm the diagnosis histopathologically.
. To reduce intraoperative blood loss and facilitate surgical resection.
. To promote bone healing and ossification within the cyst.
. To prevent pathological fractures during surgery.

Correct Answer & Explanation

. To reduce intraoperative blood loss and facilitate surgical resection.

Explanation

Preoperative selective arterial embolization is commonly used for large, highly vascular Aneurysmal Bone Cysts, especially in the spine or pelvis. Its primary role is to reduce intraoperative blood loss, making subsequent surgical curettage or resection safer and more manageable. While it can sometimes lead to cyst regression (and in some very select cases, may be used as primary treatment for truly inaccessible lesions), it is not typically considered definitive monotherapy for most surgically accessible ABCs and does not confirm diagnosis or prevent fracture during surgery itself.

Question 5012

Topic: 10. Pathology and Oncology

A 6-year-old child presents with a painful, rapidly expanding lesion in the distal femur. Biopsy reveals features consistent with an Aneurysmal Bone Cyst. Due to the proximity to the growth plate, the surgeon opts for intralesional sclerotherapy with polidocanol. What is the main advantage of sclerotherapy in this scenario?

. It provides immediate structural stabilization.
. It definitively cures all ABCs with a single injection.
. It minimizes the risk of physeal damage compared to extensive curettage.
. It eliminates the need for any subsequent imaging.
. It works by causing immediate complete bone necrosis.

Correct Answer & Explanation

. It minimizes the risk of physeal damage compared to extensive curettage.

Explanation

Intralesional sclerotherapy with agents like polidocanol is an increasingly recognized treatment option for ABCs, especially in challenging locations or in young children where extensive surgery might risk growth plate damage. Its main advantage in this scenario is minimizing the risk of iatrogenic physeal damage compared to aggressive surgical curettage, while still achieving lesion regression. It does not definitively cure all ABCs with a single injection, does not provide immediate structural stability, and requires ongoing imaging follow-up.

Question 5013

Topic: 10. Pathology and Oncology

A biopsy specimen from a bone lesion shows multiple blood-filled spaces separated by fibrous septa containing fibroblasts, hemosiderin-laden macrophages, and scattered multinucleated giant cells, with areas of reactive woven bone formation. No overtly malignant cells are seen. This histological picture is most consistent with:

. Fibrous Dysplasia
. Giant Cell Tumor
. Aneurysmal Bone Cyst
. Chondrosarcoma
. Osteomyelitis

Correct Answer & Explanation

. Aneurysmal Bone Cyst

Explanation

The described histological features – multiple blood-filled spaces, fibrous septa with fibroblasts, hemosiderin, scattered multinucleated giant cells, and reactive woven bone – are classic for an Aneurysmal Bone Cyst. While Giant Cell Tumors also contain numerous giant cells, they lack the characteristic large blood-filled cystic spaces separated by fibrous septa, and the stromal cells are the true neoplastic component. Fibrous dysplasia has characteristic 'Chinese character' trabeculae of immature woven bone. Chondrosarcoma would show malignant cartilage, and osteomyelitis would show inflammatory infiltrates and necrosis.

Question 5014

Topic: Bone Tumors

What is the characteristic appearance of the periosteum associated with an Aneurysmal Bone Cyst on plain radiographs?

. Solid periosteal reaction (Codman's triangle).
. Absent periosteal reaction.
. Thin, 'blown-out' or 'eggshell' periosteal shell.
. Lamellated periosteal reaction (onion skin).
. Sunburst periosteal reaction.

Correct Answer & Explanation

. Thin, 'blown-out' or 'eggshell' periosteal shell.

Explanation

Aneurysmal Bone Cysts are typically expansile, causing thinning and ballooning of the overlying cortex and periosteum, often described as a 'blown-out' or 'eggshell' appearance. This indicates a relatively slow but continuous expansion that allows the periosteum to form a reactive shell. Solid periosteal reaction (Codman's triangle) and sunburst appearance are often associated with aggressive or malignant lesions like osteosarcoma. Lamellated (onion skin) is seen with Ewing sarcoma or osteomyelitis. Absent periosteal reaction is unlikely in a rapidly expanding lesion.

Question 5015

Topic: Bone Tumors

A 20-year-old male with a history of an Aneurysmal Bone Cyst in the proximal tibia, treated with curettage and cryotherapy 5 years ago, now presents with recurrence. The new lesion is smaller but symptomatic. What is the most appropriate next step in management?

. Initiate systemic chemotherapy.
. Perform a second curettage with adjuvant, potentially more aggressive.
. Observe with serial imaging, as recurrence typically resolves spontaneously.
. Administer palliative radiation therapy.
. Amputation of the affected limb.

Correct Answer & Explanation

. Perform a second curettage with adjuvant, potentially more aggressive.

Explanation

For a recurrent Aneurysmal Bone Cyst, especially if symptomatic, a second surgical intervention (repeat curettage) with adjuvant therapy is often the most appropriate next step. The adjuvant may be more aggressively applied or a different one used. While embolization could be an option depending on the lesion, systemic chemotherapy is not indicated, observation is inappropriate for a symptomatic recurrence, palliative radiation is reserved for very specific refractory or inaccessible cases, and amputation is a last resort rarely necessary for ABCs.

Question 5016

Topic: 10. Pathology and Oncology

Which of the following is NOT a common differential diagnosis for an Aneurysmal Bone Cyst, especially when considering lesions with fluid-fluid levels?

. Telangiectatic Osteosarcoma
. Giant Cell Tumor (with secondary ABC changes)
. Unicameral Bone Cyst (UBC)
. Chondroblastoma
. Ewing Sarcoma

Correct Answer & Explanation

. Telangiectatic Osteosarcoma

Explanation

Telangiectatic osteosarcoma is a critical differential due to its malignant nature and identical fluid-fluid levels. Giant Cell Tumor and Unicameral Bone Cyst can sometimes have secondary aneurysmal components or be considered in the differential depending on location and age. Chondroblastoma, while often epiphyseal and sometimes cystic, rarely presents with prominent fluid-fluid levels and has a distinct chondroid matrix. Ewing Sarcoma is a small round blue cell tumor with very different radiographic features (e.g., onion-skin periosteal reaction) and typically lacks fluid-fluid levels, making it a less common differential for ABC compared to the others.

Question 5017

Topic: Bone Tumors

In evaluating an Aneurysmal Bone Cyst, which finding on CT scan provides unique information compared to plain radiographs?

. Overall lesion size and location.
. Presence of fluid-fluid levels.
. Detailed assessment of cortical destruction and integrity.
. Identification of soft tissue extension.
. Differentiation of solid versus cystic components.

Correct Answer & Explanation

. Detailed assessment of cortical destruction and integrity.

Explanation

While MRI is superior for fluid-fluid levels and soft tissue extension, and plain radiographs show overall size/location, CT excels in providing a detailed assessment of cortical destruction, integrity, and any subtle bone matrix. It is particularly useful for surgical planning to understand the extent of cortical thinning and potential breaches. Differentiation of solid versus cystic components is best done with MRI.

Question 5018

Topic: Bone Tumors

A 16-year-old competitive athlete with an Aneurysmal Bone Cyst in the distal tibia is considering surgery. What is a key consideration for returning to high-impact sports after successful surgical treatment?

. Immediate return to sports upon wound healing.
. A period of activity restriction to allow for bone remodeling and consolidation.
. Lifelong avoidance of high-impact activities.
. Only possible if prosthetic replacement was performed.
. No specific restrictions are needed as long as pain-free.

Correct Answer & Explanation

. A period of activity restriction to allow for bone remodeling and consolidation.

Explanation

After surgical treatment of an Aneurysmal Bone Cyst, especially in a weight-bearing bone, a period of activity restriction is crucial to allow for sufficient bone remodeling and consolidation within the defect. The bone defect from curettage, even with bone grafting, takes time to regain full structural integrity. Premature return to high-impact activities carries a significant risk of pathological fracture. Lifelong avoidance is usually unnecessary, and prosthetic replacement is rarely performed for ABCs.

Question 5019

Topic: 10. Pathology and Oncology

What is the primary reason why en bloc resection is generally avoided for Aneurysmal Bone Cysts in non-expendable bones, if possible?

. Higher recurrence rates compared to curettage.
. Increased risk of malignant transformation.
. Potential for significant functional deficits and complex reconstruction.
. Inability to achieve clear margins.
. Higher cost of procedure.

Correct Answer & Explanation

. Potential for significant functional deficits and complex reconstruction.

Explanation

En bloc resection, while offering the lowest recurrence rates, is generally avoided for Aneurysmal Bone Cysts in non-expendable bones (e.g., long bones of the extremities, spine) if intralesional methods can be successfully employed. This is because en bloc resection typically involves sacrificing significant amounts of normal tissue, leading to potential for substantial functional deficits and requiring complex reconstruction (e.g., endoprosthesis, allograft-autograft reconstruction). Curettage with adjuvant therapy aims to preserve maximum normal tissue and function. En bloc resection provides excellent local control, so higher recurrence rates are incorrect.

Question 5020

Topic: Bone Tumors

Which of the following describes the most common anatomical location of Aneurysmal Bone Cysts?

. Diaphysis of long bones.
. Epiphysis of long bones.
. Metaphysis of long bones and posterior elements of vertebrae.
. Small bones of the hands and feet.
. Skull and facial bones.

Correct Answer & Explanation

. Metaphysis of long bones and posterior elements of vertebrae.

Explanation

Aneurysmal Bone Cysts most commonly occur in the metaphysis of long bones (e.g., femur, tibia, humerus) and the posterior elements of the vertebrae. They can also occur in flat bones (e.g., pelvis, scapula) and, less frequently, in the small bones of the hands and feet or the skull. Epiphyseal involvement, though possible, is less common than metaphyseal involvement. Diaphyseal location is also less common.

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