A 12-year-old patient has been referred to you following complete resection with clean margins of a high-grade malignant peripheral nerve sheath tumor of the shoulder region. The tumor measured approximately 4 cm in greatest dimension. A CT scan of the chest and a bone scan were within normal limits. The patient does not have evidence of neurofibromatosis type 1 (NF1). Which of the following treatment approaches would you recommend?

Correct Answer: D

Rationale: The correct answer is D: Observation. Given the complete resection with clean margins, normal chest CT, bone scan, and absence of NF1, observation is appropriate. Chemotherapy or radiotherapy may be considered in the presence of residual disease, positive margins, or metastasis. Chemotherapy with doxorubicin and ifosfamide may cause unnecessary toxicity without clear benefit in this scenario. Radiotherapy may be reserved for cases with high-risk features. Combining chemotherapy and radiotherapy may lead to increased toxicity without proven benefit. Observation allows monitoring for disease recurrence while minimizing unnecessary treatment side effects.

Correct Answer: b

Rationale: The correct answer is B: Decreased red blood cell count. Anemia is characterized by a decrease in the number of red blood cells, leading to a lower than normal red blood cell count. In anemia, the body cannot transport enough oxygen to tissues, leading to symptoms such as fatigue and shortness of breath. Increased hematocrit (A) and decreased hemoglobin (D) are related to anemia but not specific enough to be conclusive. Decreased serum iron (C) may be seen in iron-deficiency anemia but is not always present in all types of anemia.

Correct Answer: C

Rationale: The correct answer is C: Aplastic anemia. Aplastic anemia is characterized by a low reticulocyte production index due to bone marrow failure, leading to decreased red blood cell production and subsequently causing anemia. Thalassemia (choice A) is a genetic disorder resulting in abnormal hemoglobin production, not bone marrow failure. Vitamin B12 deficiency (choice B) can lead to macrocytic anemia, not a low reticulocyte production index. Sideroblastic anemia (choice D) is characterized by abnormal iron metabolism in the bone marrow, not bone marrow failure.

Correct Answer: D

Rationale: The correct answer is D: Vitamin K deficiency. Prolonged prothrombin time and activated partial thromboplastin time indicate impaired blood clotting, which is characteristic of vitamin K deficiency. Vitamin K is essential for synthesizing clotting factors II, VII, IX, and X. Hemophilia A (choice A) is a genetic disorder resulting in deficiency of clotting factor VIII, not vitamin K-dependent factors. Thrombocytopenia (choice B) is a condition characterized by low platelet count, not affecting clotting factor synthesis. Von Willebrand factor disease (choice C) involves a deficiency or dysfunction of von Willebrand factor, not related to vitamin K deficiency.

Correct Answer: A

Rationale: The correct answer is A because Burkitt's lymphoma is associated with translocation of c-myc gene on chromosome 8, not chromosome 18. This translocation leads to uncontrolled cell proliferation. Choice B is incorrect because Burkitt's lymphoma commonly presents with jaw or facial bone involvement in HIV patients. Choice C is incorrect as the association between Epstein Barr infection and malaria exposure in African children increases the risk of Burkitt's lymphoma. Choice D is incorrect because Burkitt's lymphoma is histologically characterized by a 'starry sky' appearance due to macrophages engulfing apoptotic tumor cells, not due to the presence of the c-myc translocation.