patients have presented with skin rash or itching on or around the involved breast. Using the Ann Arbor staging system, 83% of patients present with stage 1 localized disease while the remaining 10, 0, and 7% of patients present with what is normally regarded as more aggressive stage II, III, or IV diseases, respectively. Thus, about 17% of individuals present with a more aggressive disease that has spread from its original breast implant site to nearby lymph nodes, to areas outside of the capsule, or to more distal tissues. Diagnosis In most individuals with BIA-ALCL, the affected breast has a thickened capsule around the implant and effusion fluid between the capsule and implant. Neoplastic cells are located in and typically limited to the capsule and effusion. Histological examination of the capsules shows large anaplastic cells but cells with all the features of ALCL "hallmark" are often difficult to detect. In addition to these neoplastic cells, the capsule lesions contain, sometimes in a large excess that makes diagnosis difficult, a variety of non-malignant cells such as small lymphocytes, histiocytes, and granulocytes (the granulocytes are mostly eosinophils). The histology of palpable masses exhibit a different pathological picture: the tumor masses have multinodular areas that consist of necrosis or fibrous tissue interspaced with areas that consist of large neoplastic cells that have abundant cytoplasm and abnormally shaped nuclei within a fibrotic and chronic inflammatory cell background. Again, typical ALCL-defining "hallmark" cells may be difficult to find in these masses. The effusions show abundant, uniform-appearing, non-cohesive large cells with irregularly-shaped nuclei, prominent nucleoli and abundant cytoplasm. The histology and pathological features of diseased lymph nodes and tissues outside of the breast implant are indistinguishable from those seen in ALK-negative ALCL. The neoplastic cells in the capsules, effusions, and tissues strongly and uniformly express CD30, CD4 (75–84% of cases), EMA (48–90%), CD43 (86-95%), CD45 (44-74%), and in a far fewer percentage of cases various other marker proteins. These cells do not express ALK and often lack the characteristic surface marker proteins of T-cells. Identification of the status of these markers helps diagnose the disease. Gene and molecular abnormalities No chromosome translocations, chimeric genes, or fusion proteins have been described in BIA-ALCL although the neoplastic cells in the disease have been described to have gene copy number variations involving gains in gene copies on the p arm of chromosome 19 and losses of gene copies in