Leukaemic Ascites and Peritoneal Myeloid Sarcoma: Rare but Not Impossible

A myeloid sarcoma is an extramedullary tumour arising from infiltration by leukemic cells at an anatomic site other than the bone marrow. Most commonly it precedes acute myeloid leukaemia but occasionally occurs simultaneously. It may also be associated with myeloproliferative neoplasms, myelodysplastic syndrome and the blast phase of chronic myeloid leukaemia. The most common sites for extramedullary tumours are bone, periosteum, soft tissue, lymph node and skin. Although this disease can affect a wide range of body sites, there are very few reports of peritoneal myeloid sarcoma or cavity effusion. The authors present the case of a 68-year-old man with myelodysplasia-related acute myeloid leukaemia and peritoneal myeloid sarcoma with myeloid ascites. The definitive diagnosis is challenging, requires a high level of suspicion, and relies on the exclusion of all alternative diagnoses and especially on complementary tests such as flow cytometry and immunohistochemistry analysis of ascitic fluid in order to detect the immature myeloid cells. LEARNING POINTS: Myeloid sarcomas are extramedullary leukemic tumours that occur before or simultaneously with acute myeloid leukaemia, other myeloproliferative neoplasms or myelodysplastic syndrome. Myeloid sarcomas are most often seen in bone, soft tissue, lymph node and skin, but can present in most locations. Peritoneal myeloid sarcoma and leukemic ascites, although very rare, must be searched for when a patient with acute leukaemia presents with newly diagnosed ascites, through ascitic fluid flow cytometry and immunophenotypic analysis.