To investigate the clinical presentation, clinicopathologic features, diagnosis and differential diagnosis of adult T cell leukemia/lymphoma (ATLL).

Four cases of ATLL from Fujian Cancer Hospital between October 2017 and May 2018 were analyzed using hematoxylin-eosin and immunohistochemical stains and polymerase chain reaction (PCR) for HTLV-1 provirus genes. The relevant literature was reviewed.

There were two males and two females, age range 38-80 years. All patients were from coastal cities of Fujian province. Clinical presentations including lymphadenopathy, hepatomegaly and splenomegaly were detected in most patients; skin lesion, hypercalcemia and lymphocytosis were also commonly detected.Histologically, there was diffuse effacement of the normal architecture by tumor cells infiltration. The inflammatory background is usually sparse, with scanty eosinophils. The atypical lymphoid cells were typically medium to large sized with pronounced nuclear pleomorphism, irregular nuclei, chromatin clumping and prominent nucleoli. Blast-like cells with transformed nuclei were present in variable proportions. Giant cells with convoluted or cerebriform nuclear contours may be present. Rare cases may be composed predominantly of anaplastic tumor cells. Characteristic "flower cells" with large multi-lobated nuclei can be seen. The tumor cells were strongly positive for CD2, CD3, CD5, CD4 and CD25, but negative for CD7, CD8 and cytotoxic molecules (including TIA-1, Granzyme B and perforin). In three cases, the large transformed cells were positive for CD30. In one case, the anaplastic large cells were diffusely and strongly positive for CD30. All cases were negative for EBER, but positive for HTLV-1 provirus.

ATLL is a rare type of T cell lymphoma with unique clinical and pathological features, and should be distinguished from peripheral T cell lymphoma, NOS, ALK negative anaplastic large cell lymphoma and mycosis fungoides. Hypercalcemia, systemic disease, characteristic "flower cells" and specific immunophenotypic profile of CD3⁺, CD4⁺, CD25⁺, and CD7^- are highly suggestive. However, ATLL can only be confirmed if the presence of HTLV-1 provirus.

Human T-lymphotropic virus 1; Leukemia-lymphoma, adult T-cell; Hypercalcemia; Diagnosis, differential