Primary breast lymphoma (PBL) is a very rare form of non-Hodgkin's lymphoma (NHL). A primary T-cell lymphoma in the breast with no previously identified lymphomatous lesions is an even rarer form of this malignancy.A biopsy of a breast mass in a 60-year-old Caucasian man showed a morphologic-immunophenotypic profile with features characteristic of an ALK-positive (AKT+), anaplastic large cell lymphoma. Fluorescence in situ hybridization (FISH) analysis of fixed, paraffin-embedded tissue of this lesion was performed at our institution for IRF4/DUSP22 gene rearrangement. No rearrangement was detected. The patient presented with mutations in the following genes; BCOR_p.Q600X, DNMT3A_p.F609fs, NOTCH1_p.P2320fs, and IDH2_p.R140Q. However, the patient's consultation was complicated by the fact that he had been diagnosed with breast cancer at a local hospital and had come to our institution for further consultation. The histology findings were confirmed by immunohistochemistry and FISH. Computed tomography and positron emission tomography did not reveal nodules elsewhere in the body, which allowed the staging of the patient to be completed. However, although the patient had previously received the chemotherapy CCOP regimen (ie, cyclophosphamide, vincristine, prednisolone acetate) he did not go into remission in a timely manner and relapsed after six months, followed by a drastic deterioration in his condition after four months, resulting in his death in less than one month.This report of a male patient describes a case of a rare T-cell lymphoma of the breast that occurs considerably more frequently in female patients. The differential diagnosis of the histology of this tumor showed mutations that occur more often in lymphoblastic lymphoma or leukemia. This rare malignancy and associated mutations led to the death of this patient during treatment.© 2023 Wang et al.