OBJECTIVETo study the clinicopathologic features and differential diagnosis of small cell variant of peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS).

METHODSThe clinicopathologic features of 5 cases of small cell variant of PTCL, NOS were retrospectively reviewed, with immunohistochemical study, T-cell receptor (TCR) gene rearrangement analysis and evaluation for Epstein-Barr virus (EBV) status.

RESULTSAll the 5 patients were males. The mean age was 52.6 years. The median duration before diagnosis was 1 month. Clinically, 3 patients presented in stage IV and 2 in stage III. Four of them had generalized lymphadenopathy and splenomegaly. Hepatomegaly and massive effusion were found in 1 and 2 cases, respectively. Marrow involvement was detected in 3 of the 4 patients with bone marrow biopsy performed and one of them also accompanied by lymphocytosis. Histologically, the involved lymph nodes showed partial or complete effacement of nodal architecture and replacement by a monomorphous population of small lymphoid cells. Scanty large lymphoid cells were also identified in 4 cases. Increase in number of blood vessels was noticed in two of them as well. Immunohistochemically, the lymphoma cells in all cases expressed two or more of the T-cell markers and CD43. The staining for CD20, TdT, CD56 and granzyme B was negative. CD99 expression was noted in 3 of the 4 cases. The Ki-67 index ranged from 5% to 15%. Clonal TCRgamma gene rearrangement was detected in the 4 cases studied and one of them also showed TCRbeta gene rearrangement. In-situ hybridization for EBV-encoded RNA was negative in the 4 cases studied. Follow up information was available in 3 of the 5 cases. All of the 3 patients died of the disease, with an average survival of 21.7 months.

CONCLUSIONSmall cell variant of PTCL, NOS represents a rare disease entity which often presents in advanced tumor stage and carries a poor prognosis.