Clinical example of BIA-ALCL. Patient is a 42-year-old woman who presented with a late periprosthetic seroma of the left breast capsule (A) ∼7 years following cosmetic augmentation-mastopexy with bilateral textured breast implants. A fine needle aspirate (FNA) of the periprosthetic effusion demonstrated clonal expansion of CD30⁺ large anaplastic T cells. (B) A preoperative PET/CT scan demonstrated a posterior capsule wall mass invading the chest wall. (C) Specimen from a bilateral explantation; total capsulectomy with excision of the skin involvement demonstrated a posterior mass on the capsule. Complete surgical excision is essential as residual disease is associated with disease progression.