An otherwise healthy 18-year-old female is diagnosed with high-risk neuroblastoma after presenting with fatigue and bony pain. Imaging findings demonstrate a left adrenal mass with multiple osseous metastases. She successfully completes standard therapy for high-risk neuroblastoma, but experiences several episodes of disease recurrence and ultimately dies of her disease 10 years after her initial diagnosis. During her treatment, her tumor was sent for molecular analysis. Of the following, what molecular aberration was most likely to have been detected?

Correct Answer: C

Rationale: The correct answer is C: ATRX mutation. In neuroblastoma, ATRX mutations are associated with poor prognosis and increased risk of disease recurrence. This mutation disrupts chromatin remodeling, leading to genomic instability and aggressive tumor behavior. ETV6-NTRK3 gene fusion (Choice A) is more commonly associated with pediatric mesenchymal tumors. PTPN11 mutation (Choice B) is typically found in Noonan syndrome and other malignancies, not neuroblastoma. WT1 mutation (Choice D) is more commonly seen in Wilms tumor, not neuroblastoma. In summary, the ATRX mutation is the most likely molecular aberration detected in this case based on the clinical presentation and outcomes of the patient.

Correct Answer: D

Rationale: The correct answer is D: Thrombomodulin. Thrombomodulin binds to thrombin and changes its function from procoagulant to anticoagulant by activating protein C. This leads to the downregulation of fibrinogen formation. Protein C (choice A) and its cofactor Protein S (choice B) are involved in the anticoagulant pathway but do not directly alter thrombin's function. Antithrombin (choice C) inhibits thrombin and other coagulation factors, but it doesn't specifically change thrombin's function from procoagulant to anticoagulant.

Correct Answer: B

Rationale: The correct answer is B. Platelet transfusions are rarely successful in patients with autoimmune thrombocytopenia. Rationale: 1. Patients with autoimmune thrombocytopenia have low platelet levels due to immune destruction. 2. Platelet transfusions may not be effective as the underlying autoimmune process continues to destroy transfused platelets. 3. Reviewing transfusion records of these patients would likely show low success rates of platelet transfusions. Summary of Incorrect Choices: A: Frozen storage of platelets increasing units available is not directly related to the success of platelet transfusions in autoimmune thrombocytopenia. C: Platelet units do carry a risk of transmitting hepatitis C infection, so this conclusion is incorrect. D: Preference for pooled donor platelets over single-donor platelets does not address the success of platelet transfusions in autoimmune thrombocytopenia.

Correct Answer: D

Rationale: The correct answer is D: Transmembrane iron exporter. Ferroportin is a transmembrane protein that functions as an iron exporter, allowing iron to move out of cells. This is crucial in iron metabolism as it facilitates the release of iron from cells into the bloodstream for transport to other tissues. A: A form of storage iron in intestinal mucosal cells - This is incorrect as ferroportin is not involved in storing iron in cells. B: A transport protein in the plasma - This is incorrect as ferroportin is not primarily a plasma protein but rather a transmembrane protein. C: A receptor protein on the surface of erythroid progenitors - This is incorrect as ferroportin is not a receptor protein but an exporter protein.

Correct Answer: A

Rationale: The correct answer is A: Extremity. Rhabdomyosarcoma in extremities has a worse prognosis due to difficulties in achieving complete surgical resection and higher risk of metastasis. Extremity tumors are often larger and more challenging to remove completely, leading to a higher chance of recurrence and poor outcomes. Prostate (B) and neck (D) sites are more favorable as they are easier to access for surgery and have lower rates of metastasis. Infratemporal fossa (C) is also a difficult site, but extremity tumors generally have a worse prognosis due to their anatomical and surgical challenges.