Adult T‐cell leukemia/lymphoma (ATLL) is a postthymic lymphoproliferative neoplasm of T cells caused by human T‐cell lymphotropic virus (HTLV‐1). Most cases are found in Japan, the Caribbean basin, and West Africa.

To identify diagnostic parameters for cytology in this neoplasm, the authors undertook a retrospective review of all ATLL samples from 1990 to 2000.

One hundred fourteen samples from 34 patients with the diagnosis of ATLL were reviewed: 80 cerebrospinal fluids, 7 pleural effusions, 4 bronchoalveolar lavages, 2 peritoneal effusions as well as fine‐needle aspirations of 15 lymph nodes, 4 subcutaneous lesions, and 2 breast nodules. Twenty‐one patients were women and 13 were men, with an age range of 30 to 71 years. Morphologically, all specimens were characterized by the presence of a polymorphous population of lymphocytes ranging from small bland‐appearing lymphocytes to large atypical ones with bizarre, multilobulated nuclei (flower‐like or clover leaf cells) with coarse chromatin and prominent nucleoli. The cytoplasm was deeply basophilic with occasional vacuoles. Immunocytochemistry was performed on 17 specimens from 14 patients. In all cases tested, tumor cells were immunoreactive for CD3, CD4, CD5, and CD25 and were nonimmunoreactive for CD7 and CD8. Flow cytometry was performed on 12 specimens from 9 patients. The tumor cells in all cases tested were positive for CD2, CD3, CD4, CD5, and CD25 and were negative for CD7.

Despite the polymorphous nature of ATLL, diagnosis can be established by close attention to nuclear cytologic features in conjunction with ancillary studies such as immunocytochemistry and/or flow cytometry. Cancer (Cancer Cytopathol) 2002. © 2002 American Cancer Society. Cancer (Cancer Cytopathol) 2002. © 2002 American Cancer Society.