Background: Breast cancer in the male transgender patient is a great challenge for the medical team, because it is completely different from the usual clinical scenario and there is a lack of scientific knowledge and protocols for managing this special medical situation. Case presentation: We present a 32-year-old transmasculine patient, who developed a palpable nodule on the left breast during the androgen hormonal treatment. Imaging showed a BIRADS5 nodule and core biopsy detected a luminal B breast invasive carcinoma (IDC) with androgen receptor expression. He underwent a gender reaffirmation oncological mastectomy, chemotherapy and hormonal therapy. Conclusion: In the transgender male scenario, the surgical technique should take into consideration the patient’s aesthetical desire and the oncological result. In this context, it is controversial if the hormonal and oncological therapies should also be changed.