Myeloid Sarcoma (MS) is a common condition characterized by proliferation of immature myeloid cells in extramedullary sites. It most often develops in patients with Acute Myelogenous Leukaemia (AML), myeloproliferative neoplasms or myelodysplastic syndromes. MS in AML may precede the disease, appear during the onset or as a relapse, especially in patients after bone marrow transplantation (BMT). Although MS can present in various parts of the body, the most common sites are lymph nodes, central nervous system, bones and soft tissues. MS of the gynaecologic tract is rare, especially in the cervix and uterus.

We report an unusual case of EM relapse in the uterus without evidence of a bone marrow (BM) recurrence, two years after an allogeneic BMT.

A nulliparous female 32 years old patient was currently attending the hematologic service at a quaternary Brazilian Naval Hospital since 2018, due to AML. She had no specific molecular mutation in the diagnosis. The patient was submitted to an unrelated BMT after her second complete remission in 2020 and had a relapse nine months after, with loss of variable number of tandem repeats (VNTR) from the donor and minimum residual disease (MRD) positive. Donor's Lymphocytes were infused twice and chemotherapy with a hypomethylating agent and BCL-2 inhibitor Venetoclax was established. The patient achieved her third complete remission and was in follow-up until she presented herself with complains of neuropathic and acute abdominal pain. Clinical examination revealed several soft tissue tumorations resembling MS. During the investigation, an abdominal pelvic magnetic resonance imaging (MRI) peculiarly demonstrated a large uterine mass with compression of the right ureter and pyelocalyceal dilation. Gynaecological clinical exam showed a large violaceus mass about four cm with anterior and right vaginal wall infiltration. The first diagnostic hypothesis was primary cervical cancer stage IV.

The biopsy revealed a massive infiltration of immature myeloid cells with the expression of anti-ERG and myeloperoxidase antibodies, confirming MS. The immunophenotypical analysis of the bone marrow aspirates showed the patient still had a complete remission with MRD negative and a VNTR with full donor chimerism. The patient started systemic chemoterapy with a hypomethylating agent and BCL-2 inhibitor Venetoclax.

Decision making on the treatment of cervical MS is challenging due to the absence of gynaecological classification guidelines. In patients in this age group with no offspring, the choice of therapy should consider the fertility issue, covering from hysterectomy to radiation, with or without a second BMT.

Finally, MS should be a differential diagnosis in a patient with a uterine mass and a previous medical history of AML and BMT.