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 661
Topic: 10. Pathology and Oncology
A 55-year-old male presents with a painful, 8 cm destructive, calcified lesion in his right ilium. Core needle biopsy confirms a Grade 2 conventional chondrosarcoma. What is the most appropriate definitive management?
Correct Answer & Explanation
. Wide surgical resection alone
Explanation
Conventional chondrosarcoma is notoriously resistant to both chemotherapy and radiation. The mainstay of treatment for intermediate/high-grade or pelvic chondrosarcomas is wide surgical resection alone.
Question 662
Topic: Bone Tumors
A 16-year-old male presents with knee pain and a palpable mass. Radiographs show a "sunburst" periosteal reaction and Codman's triangle in the distal femoral metaphysis. Biopsy confirms high-grade, intramedullary osteosarcoma without systemic metastasis. What is the standard of care for definitive management?
Correct Answer & Explanation
. Neoadjuvant chemotherapy followed by wide surgical resection and adjuvant chemotherapy.
Explanation
The standard treatment for high-grade osteosarcoma consists of multi-agent neoadjuvant chemotherapy, followed by wide surgical resection (limb-salvage when feasible), and subsequent adjuvant chemotherapy. Osteosarcoma is highly radioresistant, making radiation therapy generally ineffective for primary local control.
Question 663
Topic: 10. Pathology and Oncology
A 14-year-old girl presents with a rapidly expanding, painful lytic lesion in the proximal tibia. MRI demonstrates multiple cystic spaces with fluid-fluid levels. Biopsy confirms an aneurysmal bone cyst (ABC). What underlying genetic alteration is most commonly associated with primary ABCs?
Correct Answer & Explanation
. USP6 (t(16;17)) gene rearrangement
Explanation
Primary aneurysmal bone cysts are neoplastic processes driven by rearrangements of the USP6 gene, most commonly t(16;17). This rearrangement leads to upregulation of USP6, driving the destructive and expansile growth characteristic of ABCs.
Question 664
Topic: 10. Pathology and Oncology
An 8-year-old boy presents with progressive thigh pain, fever, and weight loss. Radiographs reveal a permeative diaphyseal lesion in the femur with a prominent "onion-skin" periosteal reaction. Cytogenetic testing reveals a t(11;22) chromosomal translocation. What fusion protein is generated by this mutation?
Correct Answer & Explanation
. EWS-FLI1
Explanation
Ewing sarcoma is classically characterized by the t(11;22)(q24;q12) translocation. This chromosomal abnormality results in the fusion of the EWSR1 gene on chromosome 22 with the FLI1 gene on chromosome 11, creating the EWS-FLI1 fusion protein.
Question 665
Topic: 10. Pathology and Oncology
A 50-year-old male presents with a 6-month history of dull, aching pain in his left proximal humerus, not relieved by rest. Radiographs reveal a lytic lesion with punctate and ring-and-arc calcifications within the medullary cavity, associated with cortical thickening and periosteal reaction. Which of the following is the most appropriate initial diagnostic step?
Correct Answer & Explanation
. CT-guided core needle biopsy
Explanation
Correct Answer: BThe patient's age, insidious pain, and radiographic findings (lytic lesion with chondroid matrix calcifications, cortical thickening, and periosteal reaction) are highly suspicious for a chondrosarcoma, particularly a low-grade lesion. A CT-guided core needle biopsy is the most appropriate initial diagnostic step to confirm the diagnosis, grade the tumor, and guide definitive surgical planning. This is crucial before committing to a definitive surgical procedure.Observation with serial radiographsis inappropriate given the suspicious features of malignancy.Immediate wide en bloc resectionis the definitive treatment but should only be performed after a confirmed diagnosis and precise staging.Intralesional curettageis inadequate for chondrosarcoma due to high recurrence rates and is generally contraindicated for malignant lesions.Empiric systemic chemotherapyis not indicated as chondrosarcomas are largely resistant to chemotherapy, and a definitive diagnosis is required before any systemic treatment.
Question 666
Topic: 10. Pathology and Oncology
A 45-year-old female is diagnosed with a Grade 2 conventional chondrosarcoma of the distal femur. Imaging shows no evidence of metastatic disease. What is the most crucial principle in the surgical management of this tumor?
Correct Answer & Explanation
. Wide en bloc resection with clear surgical margins
Explanation
Correct Answer: CWide en bloc resection with clear surgical margins is the gold standard and most crucial principle in the surgical management of conventional chondrosarcoma, especially for Grade 2 lesions. These tumors are highly resistant to chemotherapy and radiation, making surgical extirpation the primary curative modality. Achieving clear margins is paramount for local control and to prevent recurrence.Intralesional curettageormarginal excisionis associated with unacceptably high local recurrence rates for Grade 2 chondrosarcoma.Adjuvant chemotherapyandpreoperative radiation therapyare generally ineffective for conventional chondrosarcoma and are not considered primary treatment modalities, though they might be considered in very specific, high-risk, or unresectable cases, or for certain variants like mesenchymal chondrosarcoma.
Question 667
Topic: 10. Pathology and Oncology
When attempting to differentiate a benign enchondroma from a low-grade central chondrosarcoma in an appendicular skeleton lesion, which of the following radiographic features on plain film or CT is most suggestive of chondrosarcoma?
Correct Answer & Explanation
. Cortical scalloping greater than 2/3 of the cortical thickness
Explanation
Correct Answer: CCortical scalloping greater than 2/3 of the cortical thickness, or actual cortical breakthrough/destruction, is a strong indicator of a low-grade chondrosarcoma rather than an enchondroma. This signifies an infiltrative and slowly aggressive growth pattern. While lobulated morphology and internal calcifications (e.g., punctate or ring-and-arc) can be seen in both benign and low-grade malignant cartilaginous lesions, significant cortical erosion points towards malignancy.An intact sclerotic rimusually favors a benign lesion like an enchondroma.A well-defined lucent lesion in the diaphysisis a non-specific finding.High signal intensity on T2-weighted MRIis characteristic of cartilaginous lesions due to their high water content but does not reliably differentiate benign from low-grade malignant.
Question 668
Topic: 10. Pathology and Oncology
A 68-year-old male with Hereditary Multiple Exostoses (HME) presents with increasing pain and a palpable mass in a previously asymptomatic lesion on his distal femur. Radiographs show a thickened cartilaginous cap. What specific finding on imaging is most concerning for malignant transformation into a secondary peripheral chondrosarcoma?
Correct Answer & Explanation
. A cartilaginous cap thickness exceeding 2 cm in an adult
Explanation
Correct Answer: CIn a patient with Hereditary Multiple Exostoses, an increase in pain and a cartilaginous cap thickness exceeding 1-2 cm (with 2 cm often used as a more definitive cutoff in adults) on an osteochondroma are highly suspicious for malignant transformation into a secondary peripheral chondrosarcoma. This is the most reliable radiographic and pathological distinguishing feature.The presence of a cartilage capis normal for an osteochondroma.A lobulated contourcan be seen in both benign and malignant cartilaginous lesions.Location in the appendicular skeletonis common for osteochondromas and does not, by itself, indicate malignancy.Pain with activitycan be a symptom of malignant transformation but is also seen in benign osteochondromas due to bursitis, fracture, or nerve impingement; therefore, it is less specific than cap thickness.
Question 669
Topic: 10. Pathology and Oncology
Which of the following is considered the single most important prognostic indicator in conventional chondrosarcoma?
Correct Answer & Explanation
. Histological grade (Grade 1, 2, or 3)
Explanation
Correct Answer: CThe histological grade (Grade 1, 2, or 3) is the single most important factor in determining the prognosis of conventional chondrosarcoma. It directly correlates with the tumor's metastatic potential, local recurrence risk, and overall patient survival. Higher grades (Grade 2 and especially Grade 3) are associated with a significantly worse prognosis.Whiletumor sizeandlocation(axial lesions generally having a worse prognosis due to difficulty in achieving wide margins) do impact management and can influence prognosis, they are secondary to the histological grade.Patient ageandduration of symptomsare less direct prognostic indicators compared to the tumor's intrinsic biological aggressiveness as reflected by its grade.
Question 670
Topic: 10. Pathology and Oncology
A 60-year-old patient with a history of a resected Grade 1 chondrosarcoma of the rib presents with a new, rapidly growing mass at the previous surgical site. Biopsy reveals a high-grade pleomorphic sarcoma with no cartilaginous matrix. What is the most likely diagnosis?
Correct Answer & Explanation
. Dedifferentiated chondrosarcoma
Explanation
Correct Answer: CThe scenario describes a recurrence of a previously resected low-grade chondrosarcoma, but this time with a high-grade, non-cartilaginous sarcomatous component (pleomorphic sarcoma). This abrupt change in histology from a well-differentiated conventional chondrosarcoma to a high-grade, non-cartilaginous sarcoma is the hallmark of dedifferentiated chondrosarcoma. This variant carries a very poor prognosis.Recurrent Grade 1 conventional chondrosarcomawould retain its low-grade cartilaginous features, which is not consistent with a high-grade pleomorphic sarcoma.Post-radiation sarcomawould require a history of radiation to the area, which is not mentioned in the vignette.Metastatic carcinomais less likely given the history of a primary bone sarcoma at the same site.A new primary osteosarcomais possible but less likely than dedifferentiation given the direct history of chondrosarcoma at the same site.
Question 671
Topic: 10. Pathology and Oncology
A 50-year-old patient undergoes wide en bloc resection for a Grade 2 conventional chondrosarcoma of the proximal femur. Postoperative MRI at 6 months shows no evidence of local recurrence. What is the most appropriate long-term follow-up strategy for this patient?
Correct Answer & Explanation
. CT scan of the chest, abdomen, and pelvis every 6 months for 2 years, then annually.
Explanation
Correct Answer: CFollow-up for resected chondrosarcoma, especially Grade 2 or higher, typically involves surveillance for both local recurrence and distant metastases. The lungs are the most common site of metastasis. A comprehensive strategy involves regular imaging. For a Grade 2 chondrosarcoma, aggressive surveillance is warranted, usually involving CT of the chest, abdomen, and pelvis every 6 months for 2 years, then annually, to detect both lung and other potential metastases, as well as local recurrence (often with MRI of the local site).No further imagingis negligent for a malignant tumor.Annual chest X-rayis insufficient as CT is more sensitive for detecting lung metastases.MRI of the local site and chest X-rayis better but still insufficient due to the lower sensitivity of X-ray compared to CT for lung metastases.Bone scan every year indefinitelyis not the primary imaging modality for detecting chondrosarcoma metastases, which are typically hematogenous to the lungs.
Question 672
Topic: 10. Pathology and Oncology
Which of the following genetic mutations is most commonly associated with the development of central enchondromas and conventional central chondrosarcomas, including those seen in Ollier's disease and Maffucci syndrome?
Correct Answer & Explanation
. IDH1/IDH2
Explanation
Correct Answer: BSomatic mutations in Isocitrate Dehydrogenase 1 and 2 (IDH1/IDH2) genes are found in a significant proportion (approximately 50-70%) of central enchondromas and conventional central chondrosarcomas (Grades 1 and 2). They are considered early events in chondrosarcoma development and are also highly prevalent in enchondromas and chondrosarcomas associated with Ollier's disease and Maffucci syndrome. These mutations are key oncogenic drivers in chondrogenesis.TP53is a tumor suppressor gene associated with many cancers, including high-grade sarcomas, but not specifically central chondrosarcoma.MYC amplificationandTERT promoter mutationsare found in some aggressive tumors but are not as common or specific as IDH mutations in central chondrosarcoma.H3F3Amutations are characteristic of chondroblastoma, not central chondrosarcoma.
Question 673
Topic: 10. Pathology and Oncology
A 62-year-old patient undergoes an unplanned intralesional excision for what was thought to be an enchondroma of the proximal femur. Final pathology reveals a Grade 2 chondrosarcoma with positive surgical margins. What is the most appropriate next step in management?
Correct Answer & Explanation
. Re-excision with wide margins
Explanation
Correct Answer: DAn unplanned intralesional excision of a Grade 2 chondrosarcoma with positive margins necessitates a planned re-excision with wide margins. This is crucial for achieving local control and preventing recurrence and potential dedifferentiation. The goal of chondrosarcoma surgery is complete removal with clear margins, which was not achieved in the initial unplanned procedure.Observation with serial imagingis inadequate for a Grade 2 malignant tumor with known positive margins.Adjuvant radiation therapy aloneis generally ineffective for conventional chondrosarcoma due to its radioresistance.Systemic chemotherapyis not a primary treatment for conventional chondrosarcoma due to its chemorefractory nature.Palliative careis not appropriate given the potential for cure with adequate surgical intervention.
Question 674
Topic: 10. Pathology and Oncology
What is the primary reason for the inherent resistance of conventional chondrosarcoma to conventional chemotherapy and external beam radiation therapy?
Correct Answer & Explanation
. Poor vascularity and hypoxic environment of cartilaginous tissue
Explanation
Correct Answer: CThe primary reason for conventional chondrosarcoma's resistance to chemotherapy and radiation therapy is attributed to the inherent poor vascularity and hypoxic environment of cartilaginous tissue. This physiological characteristic limits drug delivery to the tumor cells and reduces the effectiveness of radiation, which relies on oxygen-dependent free radical formation to damage DNA. Chondrosarcomas generally have a slow growth rate, and while multi-drug resistance proteins can play a role, the fundamental nature of cartilage is the key factor.Rapid proliferation rateis characteristic of many chemosensitive tumors, not chondrosarcoma.Whilelack of specific growth factor receptorsandhigh expression of multi-drug resistance proteinscan contribute, the poor vascularity and hypoxia are considered more fundamental.Inability of drugs to penetrate the cartilaginous matrixis a consequence of the poor vascularity and density, rather than a separate primary reason.
Question 675
Topic: 10. Pathology and Oncology
A 15-year-old male presents with a 4-month history of progressive right distal femoral pain, worse at night. Radiographs show a mixed lytic and blastic lesion with a sunburst periosteal reaction. MRI confirms a large intramedullary mass extending to the physis but not crossing it, with a significant soft tissue component. Staging CT chest is negative for metastases. Biopsy confirms high-grade osteosarcoma. Which of the following Enneking surgical stages best describes this patient's tumor?
Correct Answer & Explanation
. Stage IIB
Explanation
The Enneking surgical staging system classifies musculoskeletal sarcomas based on three parameters: histologic grade (G), local extent of the primary tumor (T), and presence of regional or distant metastases (M). Grade (G): The biopsy confirms 'high-grade osteosarcoma', which corresponds to G2. Local Extent (T): The MRI shows a 'large intramedullary mass with a significant soft tissue component'. This indicates that the tumor has extended beyond the bone cortex and into the surrounding soft tissues, placing it in an extra-compartmental location. Therefore, it is T2. Metastases (M): The 'Staging CT chest is negative for metastases', meaning M0. Combining these, a G2, T2, M0 tumor is classified as Stage IIB. Stage IA and IB are for low-grade tumors. Stage IIA is for high-grade, intra-compartmental tumors. Stage III is for any tumor with regional or distant metastases (M1).
Question 676
Topic: Bone Tumors
A 12-year-old female is diagnosed with a high-grade osteosarcoma of the proximal tibia. Neoadjuvant chemotherapy is initiated. During treatment, she develops severe nausea, vomiting, and acute kidney injury with elevated creatinine. Which chemotherapy agent is the most likely cause of these specific toxicities?
Correct Answer & Explanation
. Cisplatin
Explanation
Correct Answer: DExplanation:Cisplatinis a platinum-based alkylating-like agent commonly used in osteosarcoma regimens. Its well-known dose-limiting toxicities include severe nausea and vomiting (highly emetogenic), nephrotoxicity (acute kidney injury), and ototoxicity (hearing loss, tinnitus). Therefore, the patient's symptoms are highly suggestive of cisplatin toxicity.Doxorubicin(Adriamycin) is an anthracycline associated with cumulative dose-dependent cardiotoxicity (dilated cardiomyopathy) and myelosuppression.Ifosfamideis an alkylating agent known for causing hemorrhagic cystitis (prevented by Mesna) and neurotoxicity.Methotrexate, especially high-dose, is associated with myelosuppression, mucositis, and nephrotoxicity, but severe nausea/vomiting are less prominent compared to cisplatin. Leucovorin is used for rescue.Etoposideis a topoisomerase II inhibitor primarily causing myelosuppression and mucositis.
Question 677
Topic: 10. Pathology and Oncology
A 17-year-old male undergoes limb salvage surgery for a distal femoral osteosarcoma. The reconstruction involves a massive allograft. During follow-up, he develops persistent pain, swelling, and erythema around the surgical site, along with elevated inflammatory markers. Aspiration of the joint reveals purulent fluid. What is the most appropriate initial management step?
Correct Answer & Explanation
. Perform an immediate surgical debridement and irrigation with hardware retention if possible.
Explanation
Correct Answer: DExplanation:The patient's presentation (persistent pain, swelling, erythema, elevated inflammatory markers, purulent fluid on aspiration) is highly indicative of a deep surgical site infection, a devastating complication following massive allograft reconstruction, especially in immunocompromised oncology patients. For a deep infection involving an allograft or prosthetic implant, immediate surgical debridement and irrigation are crucial. Cultures should be obtained during surgery to guide targeted antibiotic therapy. While antibiotics are necessary, they are rarely sufficient alone for deep infections involving implants or allografts. Delaying surgical intervention significantly increases the risk of chronic infection, allograft failure, and potentially amputation.A. Initiate a new course of systemic chemotherapy:This is inappropriate as the primary issue is infection, not recurrence. Chemotherapy would further compromise the immune system.B. Perform a CT-guided biopsy to rule out local recurrence:While recurrence is always a concern, the signs of acute inflammation and purulent fluid point strongly to infection. A biopsy would delay definitive treatment of the infection.C. Administer broad-spectrum intravenous antibiotics and obtain cultures:While antibiotics are essential, they are typically adjunctive to surgical debridement for deep implant-related infections.E. Observe with serial inflammatory markers and consider oral antibiotics:Observation and oral antibiotics are insufficient for a suspected deep infection with purulent fluid, which requires urgent surgical intervention.
Question 678
Topic: 10. Pathology and Oncology
A 68-year-old female with a long-standing history of Paget's disease affecting her left humerus presents with a rapidly enlarging, painful mass in the same bone. Radiographs show an aggressive, mixed lytic and blastic lesion. Biopsy confirms osteosarcoma. What is the most significant prognostic factor for this patient compared to an adolescent with conventional osteosarcoma?
Correct Answer & Explanation
. The presence of Paget's disease as a predisposing factor.
Explanation
Correct Answer: CExplanation:Osteosarcoma arising in the setting of Paget's disease of bone (secondary osteosarcoma) carries a significantly worse prognosis compared to conventional osteosarcoma in adolescents. This is a well-established clinical fact. The reasons for this include:Older age:Patients are typically older, often with more comorbidities, which can limit aggressive treatment.Higher tumor grade:These tumors are often high-grade.Advanced stage at presentation:They are frequently diagnosed at a larger size and/or with metastases.Poorer response to chemotherapy:Secondary osteosarcomas, including those from Paget's, tend to respond less favorably to standard chemotherapy regimens compared to primary osteosarcomas in younger patients.Therefore, the presence of Paget's disease as a predisposing factor is a significant adverse prognostic indicator. The location in the humerus is less impactful than the underlying condition. Gender is not a consistent prognostic factor. A good response to chemotherapy would be a favorable prognostic factor, but it is less likely in this scenario. The absence of metastatic disease at presentation is always favorable, but the question asks for themost significantprognostic factorcomparedto an adolescent, which points to the underlying Paget's disease.
Question 679
Topic: 10. Pathology and Oncology
During pre-operative planning for a distal femoral osteosarcoma, the MRI reveals a separate, distinct intramedullary lesion in the proximal femur, approximately 5 cm away from the primary tumor, with normal intervening marrow. This finding is most accurately described as:
Correct Answer & Explanation
. A skip lesion.
Explanation
Correct Answer: CExplanation:A 'skip lesion' in osteosarcoma refers to a separate, distinct focus of tumor within the same bone or a contiguous bone, discontinuous from the primary lesion but originating from it. The description of a 'separate, distinct intramedullary lesion in the proximal femur, approximately 5 cm away from the primary tumor, with normal intervening marrow' perfectly fits the definition of a skip lesion. These are true intraosseous metastases and necessitate a wider surgical margin to ensure complete tumor removal, as they carry a high risk of local recurrence if not adequately resected.A. A reactive bone marrow edema pattern:While edema can occur, it would typically be contiguous with the primary tumor or related to stress, not a distinct tumor focus.B. A synchronous multicentric osteosarcoma:This refers to two or more primary osteosarcomas arising independently in different bones, not a separate focus within the same bone.D. A benign fibrous cortical defect:These are common benign lesions, typically small, cortical, and have characteristic radiographic features distinct from an intramedullary tumor.E. An artifact of the MRI sequence:While artifacts can occur, a distinct lesion with normal intervening marrow is a real finding that requires careful interpretation.
Question 680
Topic: 10. Pathology and Oncology
A 16-year-old male with a distal femoral osteosarcoma undergoes neoadjuvant chemotherapy. After resection, the pathology report indicates 85% tumor necrosis. What is the most accurate prognostic implication of this finding?
Correct Answer & Explanation
. This suggests a poor response to chemotherapy and is an adverse prognostic factor.
Explanation
Correct Answer: BExplanation:The percentage of tumor necrosis after neoadjuvant chemotherapy is one of the most significant prognostic factors in osteosarcoma. A good response to chemotherapy is typically defined asgreater than 90% (or sometimes 95%) tumor necrosisin the resected specimen. This correlates with improved event-free survival and overall survival. Conversely, a poor response, such as 85% necrosis, which is less than the 90-95% threshold, is considered an adverse prognostic factor. It indicates that the tumor was relatively resistant to the chemotherapy regimen, and these patients have a higher risk of local recurrence and distant metastasis.A. This indicates an excellent response to chemotherapy and a favorable prognosis:Incorrect. 85% is below the threshold for an 'excellent' response.C. This level of necrosis is considered average and has no significant prognostic value:Incorrect. It is below the favorable threshold and is prognostically significant.D. This implies the tumor was originally low-grade, despite initial diagnosis:Incorrect. Tumor necrosis reflects response to treatment, not the original grade.E. This means that adjuvant chemotherapy is no longer necessary:Incorrect. Adjuvant chemotherapy is almost always necessary for high-grade osteosarcoma, and a poor response might even prompt consideration of modifying the adjuvant regimen.
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