Sclerosing Extramedullary Hematopoietic Tumor of the Breast

Abstract Introduction/Objective Sclerosing extramedullary hematopoietic tumor (SEMHT) is a rare tumor that occurs in patients with chronic myeloproliferative conditions. SEMHT can be seen in abdominal organs, retroperitoneum and mesentery. It can also be regarded as an advanced manifestation of myelofibrosis. SEMHT can occur singly or as multiple masses and manifests later in the disease course of CMPD. The differential diagnosis includes breast cancer, soft tissue tumor, and extramedullary hematopoiesis. Here we present a case of SEMHT in the breast. Methods/Case Report This is a 80-year-old female, who has a history of left breast ductal carcinoma in situ who underwent lumpectomy and received radiation in 2020. The patient also has Polycythemia Vera and MF. Bone marrow aspiration, Trephine biopsy imprints and Trephine and clot biopsies showed persistent myelofibrotic myeloid neoplasm involving a cellular bone marrow with marked fibrosis (MF Grade 3), megakaryoblastic hyperplasia, atypical megakaryocytes. In 3/2023, there were two small masses found in upper outer right breast by ultrasound measuring 4 mm and 3 mm in diameter. Breast biopsy sections showed scattered rare atypical cells within fibrotic stroma. They were only positive for Vimentin and Androgen Receptor (rare) within the performed immunohostochemistry panel. Ki67 proliferation index was 20%. The biopsy report was signed out as aytpical mesenchymal tumor. Resection was recommended. The resection showed same atypical cells within large sclerotic stroma. These atypical cells were scattered in the breast tissue along with sinusoidal capillarization. The atypical cells were atypical megakaryocytes highlighted with CD61. Erythrocyte precursors are highlighted with glycophorin a. Based on the clinical history and histologic features, SEMHT diagnosis was made. Results (if a Case Study enter NA) NA due to being a case study. Conclusion SEMHT is a rare tumor, that can occur in patients with CMPD. It can occur within different locations in the body, including breast. SEHMT should be kept in mind for an accurate diagnosis of the tumor and correct management of the patients.