Breast implant-associated anaplastic large-cell lymphoma (BIA-ALCL) is a rare peripheral T cell lymphoma. BIA-ALCL is a disease of the fibrous capsule surrounding the implant and occurs in patients after both breast reconstruction and augmentation. More than 300 cases have been reported so far, including two in a transgender patient. Here we describe BIA-ALCL presented with a mass in a transgender patient and the first case of BIA-ALCL in the Czech Republic. In 2007, a 33-year-old transgender male to female underwent bilateral breast augmentation as a part of his transformation to female. In June 2014, the patient developed a 5-cm tumorous mass in her left breast. Magnetic resonance imaging of the chest revealed a ruptured implant and a tumorous mass penetrating into the capsule and infiltrating the pectoral muscle. An R0 surgery was indicated-the implant, silicone gel and capsule were removed, and the tumorous mass was resected together with a part of the pectoral muscle. Histology revealed anaplastic large-cell lymphoma. The patient underwent standard staging procedures for lymphoma including a bone marrow trephine biopsy, which confirmed stage IE. The patient was treated with the standard chemotherapy for systemic ALCL-6 cycles of CHOP-21. The patient was tumor-free at the 2-year follow-up. BIA-ALCL has been reported mostly in women who received implants for either reconstructive or aesthetic augmentation. This is the third report of BIA-ALCL in a transgender person, the first in the Czech Republic. Level of Evidence V This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .