BIA-ALCL diagnosis: the relevance of cytology and flow cytometry in periprosthetic fluid analysis.

Breast implant-associated anaplastic large cell lymphoma (BIA-ALCL) is a rare T-cell non-Hodgkin lymphoma, representing less than 1% of breast neoplasms. Despite its low incidence, the increasing number of women with breast implants necessitates vigilance among clinicians and pathologists. BIA-ALCL presents in situ and invasive forms, with varying prognoses. The National Comprehensive Cancer Network guidelines recommend cytology, immunohistochemistry, and flow cytometry (FCM) for diagnosis. This retrospective study analyzed 16 periprosthetic fluid (PF) samples from suspected lymphoma cases between January 2018 and January 2024. Cytological and immunological analyses were performed using May Grünwald-Giemsa staining, and FCM with BD FACSCanto II and BD LYRIC cytometers. A 10 or 12-colour FCM panel including pan-T markers and CD30 was used. Of the 16 samples, 2 cases were diagnosed with BIA-ALCL. BIA-ALCL cases showed atypical CD4+ T-cells with large size and loss of CD3 and CD7. In contrast, the 14 reactive cases did not exhibit atypical cells. Key challenges included sample volume limitations, cell dilution, and distinguishing neoplastic cells from reactive ones, particularly in cases with low cell counts. FCM, combined with an extensive panel of pan-T markers and CD30, effectively differentiates anaplastic BIA-ALCL cells from reactive seroma. However, it should complement, not replace, traditional diagnostic methods. Recognizing pitfalls and correlating FCM findings with clinical and morphological data enhances diagnostic accuracy. FCM is a valuable tool for diagnosing BIA-ALCL but should be used alongside other methods. Accurate diagnosis depends on understanding sample-specific challenges and integrating FCM results with clinical context.