Introduction. Myeloid sarcomas (MS) are extramedullary manifestations of myeloid neoplasms, associated with conditions like acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and myeloproliferative neoplasms (MPN). MS presents as tumor masses in various body sites, often expressing myeloid or monocytic markers. This case report details an unusual biphasic MS relapse with a significant “intravascular” component. Materials and methods. A 59-year-old male with a history of JAK2-V617F positive MDS/MPN underwent allogeneic hematopoietic stem cell transplantation and presented with abdominal pain, skin lesions, and systemic symptoms. Biopsy of colonic masses was performed, and subsequent analysis was carried out. Results. The biopsy revealed a neoplasm with solid and intravascular components. The solid part was mainly composed of monocytic lineage cells expressing specific markers, with a small population of myeloid blasts. In contrast, the “intravascular” component was mainly myeloid blasts expressing different markers. Genetic analysis uncovered JAK2 (V617F) and KRAS (G12C) mutations. Despite treatment, the disease progressed, and the patient eventually passed away. Conclusions. Myeloid sarcomas are challenging to diagnose, often being mistaken for large cell lymphomas. They can manifest as isolated extramedullary relapses, with a unique molecular profile. This case stands out due to its biphasic nature, featuring distinct components with differing characteristics, which has not been documented previously in English literature. It underscores the intricate and diverse nature of myeloid sarcomas, emphasizing the need for further research to comprehend their biology and behavior effectively.