Breast implant-associated ALCL (BIA-ALCL) is a rare, but likely under-reported entity, which most commonly presents with an effusion developing between the breast implant and the host fibrous capsule that surrounds it. It has been described in association with breast implants used for post-cancer reconstructive surgery and when implanted for purely cosmetic reasons. Two different presentations are seen; presentation with an effusion alone +/- co-existing capsular contracture, without an associated mass, and presentation with a mass lesion +/- an effusion. These two presentations are associated with very different outcomes, with women presenting with effusion alone having an excellent long-term survival, even in the absence of specific therapy other than implant removal. In these women, no further therapy other than implant removal is likely necessary. In contrast, women presenting with a mass lesion have a higher rate of relapse and may require more aggressive therapy.