PELVIC ALVEOLAR RHABDOMYOSARCOMA WITH BONE MARROW INVOLVEMENT MISDIAGNOSED AS ACUTE MYELOID LEUKEMIA

A 17-year-old male presented with a 2-month history of generalized weakness, body pain, and weight loss. There was no fever or bleeding manifestations. There were no symptoms of a pelvic mass. At presentation he had bilateral submandibular and left axillary lymph node enlargement. The liver and spleen were palpable 2 cm each below the costal margin. The rest of the physical examination was normal. The hemoglobin, total leukocyte count, and platelet counts were 98 g/L, 6.4 × 109/L, and 112 × 109/L, respectively. Differential count showed 42% polymorphs, 48% lymphocytes, 2% monocytes, 1% eosinophil, 3% myelocytes, and 4% metamyelocytes. There were no blasts in the peripheral smear. A bone marrow aspirate revealed 82% blasts. Immunophenotype done on bone marrow showed MPO, CD13, and CD33 positivity in 91, 74, and 49% cells, respectively. A diagnosis of acute myeloid leukemia was made. He was induced with conventional “3+7” chemotherapy. Seven days later the bone marrow biopsy report was available, which showed round cell tumor infiltrate in small and large groups with intervening fibrosis suggestive of metastatic infiltration. MRI scans revealed diffuse marrow infiltrative process involving axial skeleton, bilateral iliac bones, ischium, and pubis. Similar lesions were noticed in bilateral femoral metaphysis and proximal shafts. A soft tissue mass was seen involving left lateral pelvic wall and pyriformis and obturator muscles. FNAC from this mass showed round cell