Rapid progression from MDS to AML with gastric submucosal tumour as an extramedullary infiltration.

We present a rare case of myeloid sarcoma in the stomach of an elderly woman initially diagnosed with anaemia. Myeloid sarcoma, an unusual extramedullary manifestation of acute myeloid leukaemia (AML), primarily affects lymph nodes, bones, spine and skin, with gastrointestinal involvement being infrequent. Despite normal results from the initial endoscopy, a follow-up examination after 4 months revealed multiple submucosal gastric tumours. These developments coincided with worsening of anaemia and an increase in peripheral myeloblasts. Pathological evaluation and immunohistochemical staining confirmed gastric extramedullary infiltration associated with AML. This case highlights the importance of comprehensive diagnostic processes when suspecting leukaemic transformations, especially in myelodysplastic syndrome (MDS). Due to financial constraints, additional critical studies such as cytogenetics and next-generation sequencing were not performed. Nonetheless, this rare case demonstrates the visual observation of rapid progression from MDS to AML and concurrent early myeloid sarcoma development in an elderly patient.