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10. Pathology and Oncology MCQs

Practice Set 261 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 5201

Topic: 10. Pathology and Oncology

A 10-year-old male with an osteosarcoma of the distal femur is planned for limb salvage. The tumor extends into the epiphysis, crosses the physis, and involves the articular cartilage. What type of reconstruction, if selected, would primarily rely on preserved soft tissue and muscle attachments for function of the new 'knee joint'?

. Endoprosthetic replacement
. Allograft reconstruction
. Autogenous fibula graft
. Rotationplasty
. Arthrodesis

Correct Answer & Explanation

. Rotationplasty

Explanation

Rotationplasty, specifically a Van Nes rotationplasty for distal femoral or proximal tibial tumors, involves resecting the tumor, rotating the distal limb 180 degrees, and reattaching it. The key advantage is that the patient's ankle joint acts as the new knee joint, and crucially, the patient's existing calf muscles (now anterior) and foot muscles provide active motion and control for the prosthetic limb. This leads to excellent functional outcomes, especially in children, with superior proprioception and endurance compared to conventional above-knee prostheses. Endoprosthetic and allograft reconstructions primarily rely on implant stability and remaining musculature, but don't create a 'new knee joint' from a native joint. Arthrodesis results in a stiff joint.

Question 5202

Topic: 10. Pathology and Oncology

What is the primary role of a Technetium-99m bone scintigraphy (bone scan) in the staging of osteosarcoma?

. To delineate the intramedullary extent of the primary tumor.
. To assess tumor necrosis after neoadjuvant chemotherapy.
. To detect synchronous multifocal disease or distant skeletal metastases.
. To evaluate neurovascular bundle involvement.
. To confirm the diagnosis of osteosarcoma before biopsy.

Correct Answer & Explanation

. To detect synchronous multifocal disease or distant skeletal metastases.

Explanation

A Technetium-99m bone scintigraphy (bone scan) is routinely used in the staging of osteosarcoma to detect synchronous multifocal lesions or distant skeletal metastases. Osteosarcoma is highly osteoblastic, and areas of increased osteoblastic activity show 'hot spots' on the scan. MRI is superior for intramedullary extent and neurovascular involvement. Tumor necrosis is assessed histologically from the resected specimen. Bone scans are sensitive but not specific for diagnosis, which requires biopsy.

Question 5203

Topic: 10. Pathology and Oncology

A 14-year-old male with an osteosarcoma of the distal femur presents with a pathological fracture. What is the most appropriate management strategy?

. Immediate surgical stabilization of the fracture, followed by definitive tumor resection.
. Initiate neoadjuvant chemotherapy immediately, then proceed with definitive tumor resection and fracture management.
. Above-knee amputation as pathological fracture is an absolute contraindication to limb salvage.
. Palliative radiation therapy to the fracture site to alleviate pain.
. Casting the limb for fracture healing, then re-evaluating for tumor treatment.

Correct Answer & Explanation

. Immediate surgical stabilization of the fracture, followed by definitive tumor resection.

Explanation

A pathological fracture in osteosarcoma increases the risk of local recurrence and systemic metastasis, but it is not an absolute contraindication to limb salvage. The general consensus is to stabilize the pathological fracture surgically with internal fixation to relieve pain, restore alignment, and prevent further tumor dissemination. This is often followed by neoadjuvant chemotherapy, and then definitive wide en bloc tumor resection including the fracture site and hardware. Immediate amputation is generally not necessary unless limb salvage becomes unfeasible due to significant contamination or other factors. Initiating chemotherapy without stabilizing the fracture would be problematic due to pain and potential for further complications. Palliative radiation is not the primary treatment goal. Casting is insufficient for tumor control or stabilization of a pathological fracture in this context.

Question 5204

Topic: 10. Pathology and Oncology

Which type of biopsy is generally preferred for suspected osteosarcoma to ensure adequate tissue for diagnosis and reduce the risk of tumor cell seeding?

. Fine Needle Aspiration (FNA)
. Incisional biopsy
. Excisional biopsy
. Core needle biopsy
. Brush biopsy

Correct Answer & Explanation

. Core needle biopsy

Explanation

Core needle biopsy is generally preferred for suspected osteosarcoma. It provides sufficient tissue for histological diagnosis, immunohistochemistry, and molecular studies, while being minimally invasive and allowing for precise planning of the biopsy tract. It causes less tissue disruption and contamination compared to an incisional biopsy. FNA often yields insufficient material for definitive diagnosis of sarcomas. Excisional biopsy is rarely performed for large, aggressive bone tumors due to extensive morbidity and potential for positive margins/contamination. Brush biopsy is not suitable for bone tumors.

Question 5205

Topic: Bone Tumors

What is the primary mechanism of action of Cisplatin in the treatment of osteosarcoma?

. Inhibition of dihydrofolate reductase
. Intercalation into DNA, leading to strand breaks
. Cross-linking DNA, forming adducts that inhibit DNA synthesis and repair
. Microtubule stabilization, inhibiting cell division
. Topoisomerase I inhibition

Correct Answer & Explanation

. Cross-linking DNA, forming adducts that inhibit DNA synthesis and repair

Explanation

Cisplatin is an alkylating-like agent (a platinum-based compound). Its primary mechanism of action involves binding to DNA and forming intra- and inter-strand cross-links and adducts. These DNA adducts interfere with DNA replication and transcription, ultimately leading to apoptosis. Methotrexate inhibits dihydrofolate reductase. Doxorubicin intercalates into DNA and inhibits topoisomerase II. Taxanes (like paclitaxel) stabilize microtubules. Topoisomerase I inhibitors include irinotecan and topotecan.

Question 5206

Topic: 10. Pathology and Oncology

In the context of osteosarcoma, what defines a 'wide margin' of surgical resection?

. Removal of the tumor with a cuff of normal tissue greater than 1 cm.
. Resection of the tumor within the pseudocapsule, but without gross tumor spillage.
. Removal of the tumor with an intact cuff of normal tissue at least 2 cm thick, free of tumor cells.
. Removal of the tumor and a portion of the surrounding reactive zone.
. Resection of the tumor ensuring no visible tumor cells at the cut edges on macroscopic inspection.

Correct Answer & Explanation

. Removal of the tumor with an intact cuff of normal tissue at least 2 cm thick, free of tumor cells.

Explanation

A 'wide margin' in oncologic surgery refers to the removal of the tumor along with a surrounding cuff of normal, uninvolved tissue that is free of tumor cells on microscopic examination. For osteosarcoma, this typically implies a margin of at least 2-3 cm of healthy tissue, both axially and circumferentially, through uninvolved tissue planes. Resection within the pseudocapsule (marginal resection) is inadequate for high-grade sarcomas and carries a high risk of local recurrence. A 1 cm margin may be considered acceptable in some specific situations (e.g., vital structures), but 2 cm is a more standard target for a 'wide' margin. Removing only the reactive zone is also inadequate.

Question 5207

Topic: Bone Tumors

A patient with osteosarcoma develops new onset hearing loss and tinnitus during chemotherapy. Which agent is the most likely culprit?

. Methotrexate
. Ifosfamide
. Doxorubicin
. Cisplatin
. Cyclophosphamide

Correct Answer & Explanation

. Cisplatin

Explanation

Cisplatin is well-known for its ototoxicity, causing sensorineural hearing loss (tinnitus and high-frequency hearing loss) which can be permanent and cumulative. It also causes nephrotoxicity and peripheral neuropathy. Methotrexate causes renal toxicity and mucositis. Ifosfamide causes hemorrhagic cystitis and neurotoxicity. Doxorubicin causes cardiotoxicity. Cyclophosphamide is associated with hemorrhagic cystitis (like ifosfamide) and myelosuppression.

Question 5208

Topic: Bone Tumors

Which osteosarcoma variant is considered an intermediate-grade surface tumor, typically presenting in the diaphysis of long bones with a cartilaginous cap and less aggressive behavior than conventional osteosarcoma?

. Parosteal osteosarcoma
. Periosteal osteosarcoma
. High-grade surface osteosarcoma
. Intracortical osteosarcoma
. Telangiectatic osteosarcoma

Correct Answer & Explanation

. Periosteal osteosarcoma

Explanation

Periosteal osteosarcoma is an intermediate-grade surface osteosarcoma that typically arises from the periosteum, often found in the diaphysis of long bones (especially tibia and femur). It has a predominantly chondroblastic differentiation, presenting with a cartilaginous cap and spiculated periosteal reaction. Its prognosis is generally better than conventional osteosarcoma but worse than parosteal osteosarcoma. Parosteal is low-grade. High-grade surface osteosarcoma is aggressive. Intracortical osteosarcoma is rare. Telangiectatic is intramedullary and highly aggressive.

Question 5209

Topic: 10. Pathology and Oncology

What is the most accurate method for assessing the extent of tumor necrosis after neoadjuvant chemotherapy in a resected osteosarcoma specimen?

. Gross pathological examination alone
. MRI signal changes pre- and post-chemotherapy
. Microscopic evaluation of multiple representative sections by a pathologist
. PET scan SUV uptake reduction
. Serum alkaline phosphatase level changes

Correct Answer & Explanation

. Microscopic evaluation of multiple representative sections by a pathologist

Explanation

The most accurate method for assessing tumor necrosis (chemotherapy response) is through microscopic evaluation of multiple representative sections from the resected tumor by a dedicated musculoskeletal pathologist. The percentage of necrotic tumor cells relative to viable tumor cells is calculated. Gross examination is insufficient. MRI and PET can suggest response but are not definitive for quantifying necrosis. Serum alkaline phosphatase changes can indicate disease activity but are not directly measuring necrosis.

Question 5210

Topic: 10. Pathology and Oncology

Which of the following is NOT a standard component of systemic neoadjuvant chemotherapy regimens for high-grade osteosarcoma?

. High-dose Methotrexate with Leucovorin rescue
. Cisplatin
. Doxorubicin
. Ifosfamide
. Vincristine

Correct Answer & Explanation

. Vincristine

Explanation

Standard neoadjuvant chemotherapy regimens for high-grade osteosarcoma typically include a combination of high-dose Methotrexate with Leucovorin rescue, Cisplatin, Doxorubicin (Adriamycin), and often Ifosfamide. Vincristine is a vinca alkaloid commonly used in other sarcomas (e.g., Ewing sarcoma) but is not a standard component of the primary chemotherapy regimen for conventional osteosarcoma.

Question 5211

Topic: 10. Pathology and Oncology
A 15-year-old male presents with a painful swelling in the proximal tibia. Biopsy confirms high-grade osteosarcoma. MRI demonstrates significant involvement of the proximal tibial physis, extending into the joint, but no neurovascular involvement. Which Enneking surgical stage best describes this scenario?
. Stage IA
. Stage IB
. Stage IIA
. Stage IIB
. Stage III

Correct Answer & Explanation

. Stage IIB

Explanation

The Enneking surgical staging system classifies tumors based on grade (G), local extent (T), and presence of metastases (M). A high-grade osteosarcoma is G2. Involvement of the physis and extension into the joint indicates that the tumor has breached its natural anatomical compartment and is thus extra-compartmental (T2). The absence of stated metastases means M0. Therefore, a high-grade (G2), extra-compartmental (T2) tumor without metastases is Stage IIB. Stage IA/IB are low-grade. Stage IIA is high-grade, intra-compartmental. Stage III implies metastases.

Question 5212

Topic: Bone Tumors

What is the typical age range for the primary peak incidence of conventional osteosarcoma?

. Under 5 years old
. 5-10 years old
. 10-25 years old
. 30-50 years old
. Over 60 years old

Correct Answer & Explanation

. 10-25 years old

Explanation

Conventional osteosarcoma has a bimodal age distribution, with the primary and largest peak incidence occurring in adolescents and young adults, typically between 10 and 25 years of age. A second, smaller peak occurs in older adults, often associated with predisposing factors like Paget's disease or prior radiation therapy. It is uncommon in very young children or middle-aged adults without predisposing factors.

Question 5213

Topic: 10. Pathology and Oncology

Which diagnostic finding is characteristic of Ewing sarcoma but NOT typically seen in conventional osteosarcoma?

. Sunburst periosteal reaction
. Codman's triangle
. T(11;22) chromosomal translocation
. Intramedullary growth
. Soft tissue mass component

Correct Answer & Explanation

. T(11;22) chromosomal translocation

Explanation

The t(11;22)(q24;q12) chromosomal translocation, leading to the EWSR1-FLI1 fusion gene, is the defining genetic hallmark of Ewing sarcoma. While both osteosarcoma and Ewing sarcoma can present with sunburst periosteal reaction, Codman's triangle, intramedullary growth, and a soft tissue mass component, the specific translocation is unique to Ewing sarcoma and distinguishes it genetically from osteosarcoma.

Question 5214

Topic: Bone Tumors

After surgical resection of a high-grade osteosarcoma, what is the recommended frequency and duration for surveillance chest CT scans to detect pulmonary metastases?

. Annually for 5 years, then every 2 years.
. Every 6 months for 2 years, then annually for 3 years.
. Every 3 months for 2 years, then every 6 months for 3 years, then annually up to 10 years.
. Only if symptoms of pulmonary metastasis develop.
. Every 2 years for life.

Correct Answer & Explanation

. Every 3 months for 2 years, then every 6 months for 3 years, then annually up to 10 years.

Explanation

The most common site of recurrence for osteosarcoma is the lung, usually within the first 2-3 years post-treatment. A rigorous surveillance protocol is crucial. A common recommendation is chest CT scans every 3 months for the first 2 years, then every 6 months for the next 3 years, and then annually up to 10 years or longer, depending on the institution and risk factors. The goal is early detection of resectable metastases to improve survival. Waiting for symptoms would be too late for curative metastasectomy.

Question 5215

Topic: 10. Pathology and Oncology

Which of the following prognostic factors has been shown to be consistently adverse in osteosarcoma?

. Tumor located in the distal femur
. Localized disease at presentation
. Female gender
. Axial skeleton involvement (e.g., spine, pelvis)
. Good response to neoadjuvant chemotherapy (>90% necrosis)

Correct Answer & Explanation

. Axial skeleton involvement (e.g., spine, pelvis)

Explanation

Osteosarcomas arising in the axial skeleton (spine, pelvis, scapula, jaw) consistently carry a worse prognosis compared to appendicular tumors. This is often due to difficulty in achieving wide surgical margins, higher rates of positive margins, and later presentation. Distal femur is the most common site and does not inherently confer a worse prognosis. Localized disease and a good response to chemotherapy are favorable prognostic indicators. Gender is not a consistent prognostic factor.

Question 5216

Topic: 10. Pathology and Oncology

A 12-year-old male with an osteosarcoma of the proximal tibia has received neoadjuvant chemotherapy. What is the preferred type of surgical margin for definitive resection to minimize local recurrence?

. Intralesional
. Marginal
. Wide
. Contaminated
. Enucleation

Correct Answer & Explanation

. Wide

Explanation

For high-grade malignant tumors like osteosarcoma, a 'wide margin' is the preferred surgical margin to minimize the risk of local recurrence. This means resecting the tumor with an intact cuff of healthy, uninvolved tissue surrounding it in all planes, ensuring no microscopic tumor cells are left behind. Intralesional (within the tumor) and marginal (within the reactive zone/pseudocapsule) resections are associated with very high rates of recurrence for high-grade sarcomas. Contaminated is not a surgical margin. Enucleation is for benign lesions.

Question 5217

Topic: 10. Pathology and Oncology

Which condition is characterized by multiple cartilaginous tumors within the bone, primarily affecting the long bones, and carries a risk of malignant transformation into chondrosarcoma, rather than osteosarcoma?

. Hereditary multiple exostoses (HME)
. Fibrous dysplasia
. Osteogenesis imperfecta
. Ollier's disease (multiple enchondromatosis)
. Paget's disease of bone

Correct Answer & Explanation

. Paget's disease of bone

Explanation

Ollier's disease (multiple enchondromatosis) is a non-hereditary disorder characterized by multiple enchondromas, which are benign cartilaginous tumors. These lesions have a significant risk (up to 25-50%) of malignant transformation into chondrosarcoma, not osteosarcoma. Hereditary multiple exostoses (HME) also predispose to chondrosarcoma. Fibrous dysplasia can rarely transform into osteosarcoma. Osteogenesis imperfecta is a brittle bone disease. Paget's disease predisposes to osteosarcoma.

Question 5218

Topic: 10. Pathology and Oncology

Which imaging finding on MRI is highly suspicious for a skip lesion in a patient with a primary osteosarcoma of the distal femur?

. A signal abnormality in the adjacent soft tissues.
. Periosteal edema and reactive changes.
. A separate, distinct intramedullary tumor focus in the proximal femur.
. Increased signal intensity within the tumor after neoadjuvant chemotherapy.
. Presence of a pathological fracture line.

Correct Answer & Explanation

. A separate, distinct intramedullary tumor focus in the proximal femur.

Explanation

A skip lesion is defined as a separate, distinct focus of osteosarcoma within the same bone or a contiguous bone, discontinuous from the primary tumor but originating from it. Therefore, a separate intramedullary tumor focus (e.g., in the proximal femur, distinct from a distal femoral primary) on MRI is the characteristic finding. Adjacent soft tissue involvement, periosteal edema, or pathological fracture are features of the primary tumor or its local complications. Increased signal intensity post-chemo would typically indicate a poor response or recurrence, not a skip lesion.

Question 5219

Topic: 10. Pathology and Oncology

Which treatment strategy is generally employed for resectable solitary or oligometastatic pulmonary metastases from osteosarcoma after initial systemic chemotherapy and primary tumor resection?

. Palliative radiation therapy to the lung nodules.
. Switching to a different systemic chemotherapy regimen.
. Surgical metastasectomy (wedge resection or segmentectomy).
. Close observation with frequent CT scans.
. Whole lung radiation therapy.

Correct Answer & Explanation

. Surgical metastasectomy (wedge resection or segmentectomy).

Explanation

For resectable solitary or oligometastatic pulmonary metastases from osteosarcoma, surgical metastasectomy (wedge resection or segmentectomy) is the standard of care and offers the best chance for long-term survival. Patients who undergo successful complete resection of lung metastases have significantly better survival rates. While further systemic chemotherapy might be considered, surgery is the first-line for resectable lesions. Palliative radiation or observation are generally reserved for unresectable or diffuse metastatic disease. Whole lung radiation is typically reserved for diffuse, unresectable disease, or patients who have undergone multiple metastasectomies, and has significant toxicity.

Question 5220

Topic: 10. Pathology and Oncology

What is the typical clinical presentation of conventional osteosarcoma in adolescents?

. Insidious onset of diffuse muscle weakness.
. Painless, rapidly growing soft tissue mass.
. Localized pain and swelling, often worse at night, sometimes with a palpable mass.
. Sudden onset of fever and malaise with joint effusions.
. Asymptomatic until a pathological fracture occurs.

Correct Answer & Explanation

. Localized pain and swelling, often worse at night, sometimes with a palpable mass.

Explanation

The typical clinical presentation of conventional osteosarcoma in adolescents is localized pain and swelling at the tumor site. The pain is often dull, aching, and characteristically worse at night or with activity, and may not respond to conservative measures. A palpable mass may develop as the tumor grows. Insidious onset of muscle weakness, painless rapidly growing soft tissue masses (unless a very large soft tissue component), and acute febrile illness with joint effusions are less typical primary presentations. While a pathological fracture can occur, most patients present with pain and swelling before that stage.

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