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. In this case, the patient has undergone complete resection of the tumor with clean margins and there is no evidence of metastasis or neurofibromatosis type 1. Given these factors, observation is the most appropriate approach as there is no indication for adjuvant chemotherapy or radiotherapy. Chemotherapy with doxorubicin and ifosfamide (Choice A) is typically reserved for cases with high-risk features such as incomplete resection or metastasis. Radiotherapy (Choice B) may be considered in certain cases, but in this scenario where surgery was curative and there is no evidence of spread, it is not necessary. Chemotherapy plus radiotherapy (Choice C) may be overly aggressive and carry unnecessary risks for a patient who has already had successful surgery. Thus, observation is the most appropriate approach in this situation.

Correct Answer: b

Rationale: Correct Answer: B - Decreased red blood cell count Rationale: 1. Anemia is defined by a decrease in red blood cells, causing decreased oxygen-carrying capacity. 2. A decreased red blood cell count is a key indicator of anemia. 3. Other choices are incorrect: A. Increased hematocrit is not expected in anemia, as it indicates a higher concentration of red blood cells. C. Decreased serum iron may be seen in iron-deficiency anemia but is not a universal finding in all types of anemia. D. Decreased hemoglobin is a common finding in anemia but is not as specific as a decreased red blood cell count.

Correct Answer: C

Rationale: Rationale: A low reticulocyte production index indicates decreased bone marrow response to anemia. Aplastic anemia is characterized by bone marrow failure leading to pancytopenia, causing anemia. Thalassemia results in microcytic anemia, not macrocytic. Vitamin B12 deficiency causes macrocytic anemia due to impaired DNA synthesis. Sideroblastic anemia leads to microcytic anemia due to defective heme synthesis. Therefore, the most likely cause of anemia in this patient with a low reticulocyte production index and normal mean cell volume is aplastic anemia.

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 a characteristic of Vitamin K deficiency. Vitamin K is essential for the synthesis of clotting factors II, VII, IX, and X. Hemophilia A (Choice A) is a genetic disorder resulting in a deficiency of clotting factor VIII, leading to prolonged activated partial thromboplastin time only. Thrombocytopenia (Choice B) is a condition characterized by low platelet count, which can lead to bleeding but does not affect clotting factors. Von Willebrand disease (Choice C) is a genetic disorder affecting von Willebrand factor and platelet function, not clotting factors.

Correct Answer: A

Rationale: The correct answer is A because Burkitt's lymphoma is associated with the translocation of the c-myc gene on chromosome 8, not chromosome 18. This translocation results in the overexpression of c-myc, leading to uncontrolled cell proliferation. Choice B is incorrect as Burkitt's lymphoma commonly presents with jaw or facial bone involvement in HIV patients. Choice C is incorrect as Burkitt's lymphoma is commonly seen in African children due to Epstein-Barr virus infection, not necessarily after malaria exposure. Choice D is incorrect as Burkitt's lymphoma is histologically characterized by a "starry sky" appearance due to the presence of numerous macrophages engulfing debris from apoptotic cells.