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10. Pathology and Oncology MCQs

Practice Set 260 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 5181

Topic: 10. Pathology and Oncology

In a patient with a suspected chondrosarcoma, which of the following statements about bone scintigraphy (bone scan) is most accurate?

. It is specific for chondrosarcoma diagnosis.
. It can reliably differentiate between enchondroma and low-grade chondrosarcoma.
. It is primarily used to detect multifocal disease or skeletal metastases.
. It is superior to MRI for assessing local tumor extent.
. It is not indicated for cartilaginous tumors due to low metabolic activity.

Correct Answer & Explanation

. It is primarily used to detect multifocal disease or skeletal metastases.

Explanation

Bone scintigraphy (bone scan) is highly sensitive for detecting areas of increased bone turnover, which can occur in both benign and malignant bone lesions. Its primary role in chondrosarcoma is for screening for multifocal disease (e.g., in syndromes like MHE or Ollier's) or detecting skeletal metastases. It is not specific for diagnosis, cannot reliably differentiate low-grade chondrosarcoma from enchondroma (as both can show increased uptake), and is inferior to MRI for local tumor extent assessment. While chondrosarcomas generally have lower metabolic activity than other sarcomas, they still typically show uptake on bone scan.

Question 5182

Topic: 10. Pathology and Oncology

What is the typical growth pattern of a low-grade conventional chondrosarcoma?

. Rapidly destructive with extensive soft tissue involvement.
. Slow-growing, often expanding the cortex and permeating marrow spaces.
. Aggressively permeative, skipping entire bone segments.
. Strictly contained within the cartilage cap, never invading bone.
. Purely exophytic, arising from the periosteum.

Correct Answer & Explanation

. Slow-growing, often expanding the cortex and permeating marrow spaces.

Explanation

Low-grade conventional chondrosarcomas are typically slow-growing tumors. They gradually expand the bone, leading to cortical thickening or erosion, and have a characteristic infiltrative growth pattern where tumor cells permeate the marrow spaces. Rapid destruction or aggressive skipping patterns are more typical of high-grade or other aggressive sarcomas. While juxtacortical chondrosarcomas are exophytic, conventional chondrosarcomas are intramedullary. The cartilage cap refers to osteochondromas, not conventional chondrosarcomas.

Question 5183

Topic: 10. Pathology and Oncology

A 28-year-old male presents with a painful mass in the pubic symphysis. Imaging shows a large lesion with chondroid matrix. Biopsy reveals a mesenchymal chondrosarcoma. Which adjuvant treatment is most appropriate for this patient following wide surgical resection?

. No adjuvant therapy is typically needed.
. Systemic chemotherapy.
. Radiation therapy alone.
. Targeted therapy with IDH inhibitors.
. Local cryoablation.

Correct Answer & Explanation

. Systemic chemotherapy.

Explanation

Mesenchymal chondrosarcoma is a high-grade, aggressive tumor that, unlike conventional chondrosarcoma, is responsive to chemotherapy. Therefore, systemic chemotherapy is typically recommended as an adjuvant therapy following wide surgical resection to address micrometastatic disease and improve survival. Radiation therapy may also be used, especially for positive margins or unresectable disease, but chemotherapy is often primary for systemic control. IDH inhibitors are not indicated for mesenchymal chondrosarcoma. Local cryoablation is not adequate for such an aggressive tumor.

Question 5184

Topic: 10. Pathology and Oncology

Which of the following factors would lead to the poorest prognosis for a patient with chondrosarcoma?

. Primary tumor located in a long bone.
. Histological diagnosis of Grade I conventional chondrosarcoma.
. Negative surgical margins (R0 resection).
. Presence of distant metastases at presentation.
. Patient age less than 40 years.

Correct Answer & Explanation

. Presence of distant metastases at presentation.

Explanation

The presence of distant metastases at presentation is the most significant negative prognostic factor for any sarcoma, including chondrosarcoma. It indicates advanced disease and is associated with significantly poorer survival rates compared to localized disease, regardless of tumor grade or location. Grade I conventional chondrosarcoma with negative margins in a long bone generally has a good prognosis. Patient age can be a factor but is secondary to metastatic disease.

Question 5185

Topic: 10. Pathology and Oncology

A 60-year-old female presents with a painful shoulder mass. Biopsy reveals a Grade II chondrosarcoma of the proximal humerus. Preoperative workup should include which of the following for staging?

. Only local radiographs of the shoulder.
. MRI of the shoulder and CT scan of the chest.
. PET-CT scan of the entire body.
. Bone scan only.
. Ultrasound of regional lymph nodes.

Correct Answer & Explanation

. MRI of the shoulder and CT scan of the chest.

Explanation

Preoperative staging for a Grade II chondrosarcoma should include local imaging with MRI to precisely delineate tumor extent for surgical planning, and a CT scan of the chest to rule out lung metastases, which is the most common site of distant spread. While a PET-CT can provide additional information, CT chest for lung metastases and local MRI are the core staging modalities. Bone scan and regional lymph node ultrasound are less routinely critical for conventional chondrosarcoma in this context.

Question 5186

Topic: 10. Pathology and Oncology
What is the primary role of percutaneous biopsy in the diagnosis of chondrosarcoma?
. To provide definitive treatment.
. To distinguish between Grade I and Grade III lesions without risk of sampling error.
. To obtain tissue for histological diagnosis and grading prior to definitive surgical planning.
. To assess tumor response to neoadjuvant chemotherapy.
. To definitively rule out infection.

Correct Answer & Explanation

. To obtain tissue for histological diagnosis and grading prior to definitive surgical planning.

Explanation

The primary role of percutaneous biopsy (core needle biopsy or incisional biopsy if core is insufficient) in chondrosarcoma is to obtain tissue for accurate histological diagnosis and grading prior to definitive surgical planning. This is crucial as management strategies vary significantly based on the diagnosis and grade. It is not for definitive treatment, can have sampling error in distinguishing grades (especially low vs. high), and is not solely for assessing therapy response or ruling out infection (though it can help).

Question 5187

Topic: 10. Pathology and Oncology

A patient undergoing neoadjuvant chemotherapy for osteosarcoma develops signs of methotrexate toxicity, including severe mucositis and myelosuppression. Which agent is primarily used to 'rescue' the patient from methotrexate toxicity?

. Filgrastim
. Leucovorin
. Mesna
. Dexrazoxane
. Allopurinol

Correct Answer & Explanation

. Leucovorin

Explanation

Leucovorin (folinic acid) is the cornerstone of methotrexate rescue therapy. It is a reduced folate that bypasses the dihydrofolate reductase enzyme, allowing normal cells to synthesize nucleic acids and continue proliferation, thereby counteracting the effects of methotrexate. Filgrastim (G-CSF) stimulates neutrophil production but is not a direct antidote to methotrexate toxicity. Mesna is used to prevent hemorrhagic cystitis with cyclophosphamide and ifosfamide. Dexrazoxane protects against doxorubicin-induced cardiotoxicity. Allopurinol prevents hyperuricemia from tumor lysis syndrome, not direct methotrexate toxicity.

Question 5188

Topic: 10. Pathology and Oncology

Which histological subtype of osteosarcoma is characterized by abundant reactive bone formation, often mistaken for a benign lesion on initial biopsy, and typically carries a better prognosis?

. Telangiectatic osteosarcoma
. Chondroblastic osteosarcoma
. Fibroblastic osteosarcoma
. Parosteal osteosarcoma
. Small cell osteosarcoma

Correct Answer & Explanation

. Parosteal osteosarcoma

Explanation

Parosteal osteosarcoma is a low-grade surface osteosarcoma characterized by a slow growth pattern, excellent prognosis, and a classic radiographic appearance of a dense, lobulated mass arising from the cortical surface, often with a 'string sign' (radiolucent line between tumor and cortex). It is predominantly composed of well-differentiated fibrous tissue and mature bone. Telangiectatic osteosarcoma is highly aggressive, lytic, and mimics aneurysmal bone cyst. Chondroblastic and fibroblastic osteosarcomas are conventional high-grade subtypes with typical aggressive behavior. Small cell osteosarcoma is rare and also highly aggressive.

Question 5189

Topic: 10. Pathology and Oncology

A 20-year-old male with a history of retinoblastoma in childhood presents with a new lesion in his proximal tibia consistent with osteosarcoma. What genetic condition links these two malignancies?

. Neurofibromatosis type 1
. Multiple hereditary exostoses
. Li-Fraumeni syndrome
. Ollier's disease
. Germline mutation of the RB1 gene

Correct Answer & Explanation

. Germline mutation of the RB1 gene

Explanation

Patients with hereditary retinoblastoma have a germline mutation in the RB1 tumor suppressor gene. This predisposes them to a significantly increased risk of developing secondary cancers, particularly osteosarcoma, later in life. This is a classic example of the 'two-hit' hypothesis. Neurofibromatosis type 1 is associated with neurofibromas, optic gliomas, and sarcomas (MPNSTs), but not specifically osteosarcoma after retinoblastoma. MHE and Ollier's disease are associated with chondrosarcoma. Li-Fraumeni syndrome involves germline TP53 mutations and is associated with various cancers including sarcomas, but the direct link with retinoblastoma and subsequent osteosarcoma is the RB1 gene.

Question 5190

Topic: 10. Pathology and Oncology

Which of the following is considered the most significant poor prognostic indicator for conventional high-grade osteosarcoma?

. Patient age between 10-20 years
. Distal femoral location
. Absence of metastatic disease at presentation
. Less than 90% tumor necrosis after neoadjuvant chemotherapy
. Alkaline phosphatase levels within normal limits

Correct Answer & Explanation

. Less than 90% tumor necrosis after neoadjuvant chemotherapy

Explanation

The most significant poor prognostic indicator for osteosarcoma is a poor response to neoadjuvant chemotherapy, typically defined as less than 90% (or sometimes 95%) tumor necrosis in the resected specimen. This indicates that the tumor is relatively resistant to the standard chemotherapy regimen and correlates with higher rates of recurrence and metastasis. Age and location (distal femur is common) are not inherently poor prognostic indicators compared to tumor response. The absence of metastatic disease at presentation is a favorable prognostic factor. Elevated alkaline phosphatase can be a poor prognostic indicator, so normal levels are relatively favorable or neutral.

Question 5191

Topic: Bone Tumors

A 12-year-old is undergoing limb salvage surgery for a distal femoral osteosarcoma. The surgeon plans to use an expandable endoprosthesis. What is the main advantage of this type of implant in a growing child?

. Lower risk of infection compared to other implants.
. It allows for limb lengthening to compensate for growth discrepancies.
. Superior bone integration due to porous coating.
. It eliminates the need for future revision surgeries.
. Reduced cost compared to fixed-length prostheses.

Correct Answer & Explanation

. It allows for limb lengthening to compensate for growth discrepancies.

Explanation

Expandable endoprostheses (also known as growing prostheses or modular growing prostheses) are designed to lengthen over time, either surgically or non-invasively, to match the growth of the contralateral limb. This is their main advantage in skeletally immature patients, as it helps prevent significant limb length discrepancy. They do not inherently have a lower infection risk, superior bone integration (unless specifically designed with unique coatings), or eliminate the need for future revisions (they often have a limited lifespan). They are typically more expensive than fixed-length prostheses due to their complex mechanisms.

Question 5192

Topic: Bone Tumors

Which osteosarcoma subtype is most likely to be purely lytic on radiographs, often mimicking an aneurysmal bone cyst, and typically has a very aggressive clinical course?

. Parosteal osteosarcoma
. Periosteal osteosarcoma
. High-grade surface osteosarcoma
. Telangiectatic osteosarcoma
. Low-grade central osteosarcoma

Correct Answer & Explanation

. Telangiectatic osteosarcoma

Explanation

Telangiectatic osteosarcoma is a rare but highly aggressive variant characterized by a predominantly lytic, hemorrhagic, and cystic appearance, often leading to misdiagnosis as an aneurysmal bone cyst. It shows minimal osteoid formation. Parosteal and periosteal osteosarcomas are surface tumors, with parosteal being low-grade and periosteal intermediate-grade, both with distinct features and generally better prognosis than conventional osteosarcoma. High-grade surface osteosarcoma is also aggressive but usually has some visible matrix. Low-grade central osteosarcoma is rare and has a better prognosis but is still an intramedullary lesion.

Question 5193

Topic: 10. Pathology and Oncology
In the Enneking surgical staging system for musculoskeletal sarcomas, what does a Stage IIB tumor represent?
. Low-grade, intra-compartmental tumor
. Low-grade, extra-compartmental tumor
. High-grade, intra-compartmental tumor
. High-grade, extra-compartmental tumor
. Metastatic disease

Correct Answer & Explanation

. High-grade, extra-compartmental tumor

Explanation

The Enneking surgical staging system classifies musculoskeletal sarcomas based on grade (G), local extent (T), and presence of metastases (M). Stage IIB denotes a high-grade (G2), extra-compartmental (T2) tumor with no regional or distant metastases (M0). Stage I is low-grade, Stage II is high-grade. 'A' indicates intra-compartmental (T1), and 'B' indicates extra-compartmental (T2). Stage III denotes any tumor with metastasis (M1).

Question 5194

Topic: 10. Pathology and Oncology

A 15-year-old with osteosarcoma of the distal femur undergoes neoadjuvant chemotherapy. Post-chemotherapy MRI shows a decrease in tumor size and signal intensity. After resection, pathology reveals 95% tumor necrosis. What is the prognostic implication of this finding?

. It suggests a poor response to chemotherapy and indicates a need for intensified adjuvant therapy.
. It is an excellent prognostic factor, indicating a favorable response to chemotherapy and better survival.
. It has no significant prognostic value and does not alter post-operative management.
. It implies the tumor was originally low-grade, despite initial diagnosis.
. It signifies that chemotherapy was unnecessary and surgery alone would have sufficed.

Correct Answer & Explanation

. It is an excellent prognostic factor, indicating a favorable response to chemotherapy and better survival.

Explanation

A high percentage of tumor necrosis (typically >90-95%) following neoadjuvant chemotherapy is considered an excellent prognostic factor in osteosarcoma. It indicates a favorable response to chemotherapy and is strongly correlated with improved event-free survival and overall survival. Conversely, poor necrosis (<90%) is a significant poor prognostic indicator. It does not imply a low-grade tumor, nor does it suggest chemotherapy was unnecessary; rather, it affirms the effectiveness of the chosen regimen. It informs, but doesn't necessarily 'alter', post-operative management, but rather guides prognostication.

Question 5195

Topic: Bone Tumors

Which of the following conditions is a known predisposing factor for the development of secondary osteosarcoma in adults?

. Fibrous dysplasia
. Multiple enchondromatosis (Ollier's disease)
. Osteomyelitis
. Paget's disease of bone
. Osteopetrosis

Correct Answer & Explanation

. Paget's disease of bone

Explanation

Paget's disease of bone is a well-established risk factor for the development of secondary osteosarcoma, especially in elderly patients. The risk is estimated to be less than 1% but is significantly higher than in the general population. Other conditions like post-radiation therapy, fibrous dysplasia, bone infarcts, and chronic osteomyelitis (rarely) can also predispose to secondary osteosarcoma, but Paget's disease is a classic association. Multiple enchondromatosis (Ollier's disease) and Maffucci syndrome are associated with chondrosarcoma. Fibrous dysplasia very rarely transforms into osteosarcoma. Osteomyelitis itself is not a direct predisposing factor for osteosarcoma.

Question 5196

Topic: 10. Pathology and Oncology

A 13-year-old presents with a large osteosarcoma of the proximal tibia involving the physis and extending into the joint. What surgical option would provide the best local control while preserving maximum function in this scenario?

. Above-knee amputation
. Resection and non-vascularized allograft reconstruction
. Resection and modular endoprosthesis reconstruction
. Resection and rotationplasty
. Resection and custom 3D-printed implant

Correct Answer & Explanation

. Resection and rotationplasty

Explanation

For a large proximal tibial osteosarcoma involving the physis and extending into the joint, particularly in a child where limb length preservation is critical, rotationplasty (specifically Van Nes rotationplasty for distal femoral/proximal tibial tumors) is often considered. It involves resecting the tumor-bearing segment, rotating the distal limb 180 degrees, and reattaching it to the proximal femur. This allows the ankle joint to function as a knee joint for prosthetic fitting, providing excellent functional outcomes, especially for active children. Amputation provides local control but sacrifices function. Allograft and endoprosthetic reconstructions are options, but an endoprosthesis faces challenges with joint reconstruction and long-term durability in a young patient, and allografts have issues with non-union, fracture, and potential infection. A custom 3D-printed implant is a type of endoprosthesis, facing similar challenges. Rotationplasty, despite its cosmetic appearance, offers superior functional results for this specific scenario.

Question 5197

Topic: 10. Pathology and Oncology

During follow-up for a 17-year-old who had limb salvage surgery for osteosarcoma of the proximal humerus, a new solitary pulmonary nodule is detected on surveillance CT scan of the chest. What is the most appropriate next step in management?

. Begin a new course of systemic chemotherapy immediately.
. Initiate palliative radiation therapy to the lung nodule.
. Perform a CT-guided biopsy of the nodule for histological confirmation.
. Surgically resect the pulmonary nodule if technically feasible.
. Observe with serial CT scans every 3 months.

Correct Answer & Explanation

. Surgically resect the pulmonary nodule if technically feasible.

Explanation

For a solitary, resectable pulmonary nodule in a patient with a history of osteosarcoma, surgical metastasectomy (wedge resection or segmentectomy) is generally the treatment of choice if there are no other active sites of disease and the patient's performance status allows. This offers the best chance for long-term survival. While a biopsy can confirm malignancy, in the context of osteosarcoma, the high likelihood of it being a metastasis (and the importance of timely resection) often leads directly to surgical excision if the lesion is accessible and deemed resectable. Systemic chemotherapy is typically reserved for multiple or unresectable metastases. Radiation is not curative for osteosarcoma lung mets. Observation is inappropriate for a potentially curable metastasis.

Question 5198

Topic: Bone Tumors

Which of the following conditions most commonly presents with osteosarcoma of the jaw, often in older adults?

. Li-Fraumeni syndrome
. Hereditary retinoblastoma
. Paget's disease of bone
. Multiple hereditary exostoses
. Fibrous dysplasia

Correct Answer & Explanation

. Paget's disease of bone

Explanation

Osteosarcomas of the jaw (mandible and maxilla) are distinct from appendicular osteosarcomas. They tend to occur in older adults and have different biological behaviors and prognoses. While Li-Fraumeni and hereditary retinoblastoma predispose to osteosarcoma, they are not specifically associated with a higher incidence in the jaw compared to the skeleton overall, and usually present at a younger age. Paget's disease of bone is a strong predisposing factor for secondary osteosarcoma in older adults, and the craniofacial skeleton (including the jaw) is a common site for Paget's disease. Therefore, Paget's disease is the most common predisposing factor for osteosarcoma of the jaw in older adults. MHE is linked to chondrosarcoma. Fibrous dysplasia can rarely undergo malignant transformation, but it's not the most common predisposing factor for jaw osteosarcoma in this age group.

Question 5199

Topic: Bone Tumors

A 16-year-old male presents with a painful mass in his distal femur. Radiographs show a dense, lobulated lesion arising from the external cortical surface, with a characteristic 'string sign' separating it from the underlying cortex. What is the most likely diagnosis?

. Conventional osteosarcoma
. Chondrosarcoma
. Ewing sarcoma
. Parosteal osteosarcoma
. Periosteal osteosarcoma

Correct Answer & Explanation

. Parosteal osteosarcoma

Explanation

The description of a dense, lobulated lesion arising from the external cortical surface, with a 'string sign' (a radiolucent line between the tumor and the underlying cortex), is pathognomonic for parosteal osteosarcoma. This subtype is typically low-grade, grows slowly, and has a much better prognosis than conventional osteosarcoma. Conventional osteosarcoma is intramedullary and aggressive. Chondrosarcoma produces cartilaginous matrix. Ewing sarcoma shows an 'onion-skin' periosteal reaction and usually a purely lytic appearance. Periosteal osteosarcoma is also a surface osteosarcoma but originates from the periosteum, has an intermediate grade, is less ossified, and lacks the 'string sign'.

Question 5200

Topic: Bone Tumors

Which component of the chemotherapy regimen for osteosarcoma is associated with hemorrhagic cystitis, and what prophylactic agent is used to prevent it?

. Methotrexate; Leucovorin
. Cisplatin; Amifostine
. Doxorubicin; Dexrazoxane
. Ifosfamide; Mesna
. Etoposide; Filgrastim

Correct Answer & Explanation

. Ifosfamide; Mesna

Explanation

Ifosfamide is an alkylating agent commonly used in osteosarcoma treatment, and its primary dose-limiting toxicity is hemorrhagic cystitis, caused by the metabolite acrolein. Mesna (2-mercaptoethane sulfonate sodium) is a uroprotectant that inactivates acrolein in the bladder, thereby preventing hemorrhagic cystitis. Leucovorin rescues from methotrexate toxicity. Amifostine reduces nephrotoxicity from cisplatin. Dexrazoxane protects against doxorubicin-induced cardiotoxicity. Filgrastim is a G-CSF used for myelosuppression, not specific to etoposide.

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