The Difficulties and Ease of Diagnosing Anaplastic Large Cell Lymphomas on Cytology.

Introduction and Objectives: Anaplastic large cell lymphoma (ALCL), a unique non-Hodgkin lymphoma (NHL), is a CD30-positive neoplasm of T-cell lineage. Its distinctive yet variable cytomorphology makes diagnosing fine needle aspiration cytology (FNAC) challenging. This study was undertaken to study the cytomorphology and the utility of immunocytochemical (ICC) stains on cytology in ALCL and to discuss their morphological differential diagnosis. Materials and Methods: The present study was conducted in the Department of Pathology of a tertiary care center. A retrospective review was done from January 2017 to July 2022, and all histopathologically and immunohistochemically (IHC) diagnosed cases of ALCL were taken and correlated with the cytological diagnosis. Results: Twenty-one cases of histopathology examination and IHC-proven cases of ALCL were retrieved from the departmental archives and reviewed. The ages ranged from 3 to 80 years (median age 28 years). Commonly noted cytomorphologic features included singly dispersed large pleomorphic cells, hallmark cells, and Reed-Sternberg-like cells. CD15, CD30, epithelial membrane antigen, and anaplastic lymphoma kinase-1 were some of the ICC stains used in this study. All 21 cases had cytology correlation. Fourteen cases had concordant cyto-histological correlation. Seven cases of histopathologically proven ALCL were reported as Hodgkin lymphoma (HL) in three, ALCL/anaplastic diffuse large B-cell lymphoma, HL/ALCL, poorly differentiated carcinoma, and NHL in one case each on cytology. Conclusion: ALCL has a reasonably distinct cytomorphologic appearance and ICC staining pattern, and a careful interpretation of both helps arrive at a reliable FNAC diagnosis.