Differential diagnosis of angioimmunoblastic T-cell lymphoma with seropositivity for anti-HTLV antibody from adult T-cell leukemia/lymphoma

Angioimmunoblastic lymphoma (AITL) is a nodal peripheral T-cell lymphoma characterized by a proliferation of arborizing vessels and hyperplastic follicular dendritic cells as well as a polymorphous lymphoid infiltrate including neoplastic cells with clear cytoplasm. Adult T-cell leukemia/lymphoma (ATLL) is caused by the retrovirus human T-cell leukemia virus type I (HTLV-I), and the neoplastic cells are usually large and pleomorphic. Recently, a rare morphologic variant of ATLL with AITL-like features has been reported. Here, we presented a case of peripheral T-cell lymphoma with morphological features of AITL in Taiwan, a country non-endemic for HTLV, and the patient was seropositive for anti-HTLV antibody, which raised the possibility of ATLL with AITL-like features. Immunohistochemically, there were hyperplastic follicular dendritic meshworks by CD21 immunostaining, and the neoplastic cells expressed CD10, programmed death-1, and CXCL13. Furthermore, Southern blot analysis using DNA extracted from the nodal tissue was negative for HTLV-I proviral integration. Our investigations indicated that in an HTLV-I non-endemic area, a peripheral T-cell lymphoma with typical morphologic and immunophenotypic features of AITL could be confidently diagnosed as AITL even if the patient was seropositive for anti-HTLV antibody.