Objective: Anaplastic large cell lymphoma (ALCL) is a rare subtype of non-Hodgkin's lymphoma that is difficult to diagnose on fine needle aspiration cytology (FNAC). Detailed descriptions about the cytomorphological features of ALCL are few and do not illustrate the various categories of cells, which we have done in this study.
Methods: Eight FNAC specimens from seven patients with biopsy-proven ALCL over a period of 6 years were reviewed. Cytomorphological details were analysed and the various cell types identified were enumerated on Papanicolaou and May-Grünwald-Giemsa (MGG)-stained smears.
Results: Of the seven cases, five were of conventional type, one of the lymphohistiocytic variant and one of the small cell variant. Aspiration from the conventional type showed a mixed population of lymphoid cells with many plasma cells. The tumour cells were intricately admixed within and distributed as single cells without grouping. Distinct hallmark cells, doughnut cells, embryo cells, tennis racket cells, cells with wreath-like nuclei, Reed-Sternberg-like cells and nondescript cells were seen. Nucleoli were rounded, occasionally tubular in shape. The tumour cells showed abundant blue cytoplasm on MGG stain with a perinuclear hoff. Aspiration from the lymphohistiocytic and small cell variants showed a small number of similar characteristic giant cells. All cases were confirmed as ALK-1 positive.
Conclusions: The morphological spectrum of ALCL is wide and it may be misdiagnosed as a metastatic poorly differentiated malignant tumour on FNAC. Identification of unusual giant cells on FNAC helps in establishing a diagnosis on an early lymph node biopsy.