A perianal presentation of myeloid sarcoma.

Myeloid sarcoma is a rare tumour associated with acute myeloid leucaemia (AML). Infrequently, it can occur in myelodysplastic/myeloproliferative overlap syndrome conditions such as chronic monomyelocytic leucaemia (CMML), where it often heralds the transformation towards an AML. We discuss a rare presentation of myeloid sarcoma in the perianal region of a 51-year-old man, who was seen by various clinicians and treated for haemorrhoids and perianal abscess. There were no gross abnormalities in initial haematological investigations and the patient was systemically well. A histological biopsy demonstrated myeloid sarcoma and bone marrow aspirate, and trephine confirmed CMML transforming to AML. Treatment of myeloid sarcoma is dependent on whether there is associated AML in the bone marrow. Dual chemotherapy with cytarabine and daunorubicin remains the gold standard treatment in these patients. Sending histology samples of atypical lesions when performing incision and drainage procedures is extremely important, as it contributes to early detection of rare and malignant tissue diagnoses.