Anaplastic large cell T-cell lymphoma: insights from cytological and immunological profiles across ten diverse cases.

While the latest WHO classification of hematological neoplasms helps refine the diagnostic criteria for anaplastic large cell lymphomas (ALCL), their diagnosis can still be challenging. This retrospective series of 10 ALCL cases illustrates the cytological appearance and immunological profile obtained through flow cytometry (FCM) from various sample types, including lymph node biopsies (LN), peripheral blood (PB), cerebrospinal fluid (CSF), and pleural fluid (PF). ALCL exhibits a polymorphic cytological appearance, ranging from "doughnut" cells to Hodgkin-like cells, very large cells, and small cells, with this polymorphism being particularly pronounced in ALK (-) forms. The detection of cytotoxic CD4+ T-cells by FCM aids in confirming the diagnosis, especially in small cell forms, which typically correspond to circulating phases. Cytological orientation, particularly for LNB, helps optimize the FCM panel to be used and ensures that ALCL, which frequently shows a loss of pan-T markers, is not overlooked. In conclusion, while the final diagnosis is histological, cytological analysis combined with FCM provides an initial diagnostic orientation for ALCL and guides complementary genetic analyses.