A rare case of isolated myeloid sarcoma of the small gut with inv(16)(p13;q22) without bone marrow involvement
A 27-year-old woman presented with recurrent, colicky abdominal pain associated with occasional vomiting for 2 months. There was no history of fever, jaundice, hematemesis, or melena. She had been hospitalized several times and treated conservatively. The patient was conscious, alert, oriented, and afebrile, and her vitals were within normal limits. No pallor, edema, jaundice, clubbing, or superficial lymph node enlargement were present. Her abdomen was soft, non-tender, and not distended. Other systemic examinations revealed no abnormality. Contrast enhanced computerized tomography of the abdomen showed a soft tissue mass lesion () in the left side of the mesentery with adherent small gut loops.\nExploratory laparotomy was performed. There was moderate ascites without liver nodules or peritoneal deposits. There was an 8.0×7.0 cm globular mass with serosal involvement in the ileum, located 40 cm proximal to the ileo-cecal junction causing luminal obstruction and proximal dilatation, with no apparent mucosal involvement and thickening of the adjacent small bowel. The involved Ileal segment was resected with a 10 cm proximal and a 5 cm distal margin, and a side-to-side ileo-ileal anastomosis was performed. On gross examination of the specimen, there was a tumor, 6 cm in diameter, extending outwards into the mesentery and protruding into the intestinal lumen. The cut surface was grayish and fleshy. A total of 10 tiny lymph nodes were seen in the mesentery. Microscopically, the small intestine showed a tumor composed of sheets of atypical large cells with moderate to scanty cytoplasm, a high nucleo-cytoplasmic ratio, and occasional prominent nucleoli. A fair number of eosinophils were also observed (, ). The tumor cells infiltrated the muscle coat of the intestine and extended up to the serosa. A morphological diagnosis of high grade NHL, large cell type vs. granulocytic sarcoma were differential diagnoses. The surgical resection margins or the lymph nodes were not involved. On IHC analysis, the tumor cells were positive for the leukocyte common antigen, CD117, CD34, myeloperoxidase (MPO), and CD43 and negative for CD20, CD3, CD5, CD10, and CD23. Thus, a final diagnosis of GS (MS) of the small gut was made. A peripheral blood smear showed apparently normal WBC counts with normal differential and platelet counts. Bone marrow aspiration showed normocellular marrow with tri-lineage differentiation. Blast counts were not increased. Conventional cytogenetics showed a normal 46, XX chromosomal pattern. Subsequently, the marrow material was assessed for the presence of common translocations by multiplex RT-PCR and inv(16)(p13;q22); CBFB-MYH11 was detected.\nIn this case, the bone marrow did not show any morphological involvement; however, the detection of the molecular marker of inv(16)(p13;q22) fulfills the criteria of AML diagnosis as defined by the World Health Organization in 2008 []. Routine biochemical parameters including serum potassium, calcium, phosphorus, and magnesium were within the reference ranges. Viral markers were negative. After proper counseling, the patient was treated with standard "3+7" daunomycin and cytarabine as remission induction followed by 3 cycles of consolidation therapy with high dose cytarabine []. The clinical course of the patient was uneventful during chemotherapy except for 2 occasions of febrile neutropenia, which were managed successfully by antimicrobials. Post consolidation, inv(16)(p13;q22) was negative from bone marrow. Post chemotherapy, she is on regular follow up and doing well.