Indolent T-lymphoblastic proliferation with disseminated multinodal involvement and partial CD33 expression.

Although indolent T-lymphoblastic proliferations (iT-LBP) are rare, this diagnosis should be excluded in any patient with an extrathymic proliferation of immature TdT+T cells. Unlike T-lymphoblastic leukemia/lymphoma, patients with iT-LBP do not require chemotherapy. We report a case of iT-LBP with disseminated multinodal involvement in an otherwise healthy 49-year-old woman. Multiple lymph node biopsies were performed over the course of several months demonstrating persistent and anatomically diffuse involvement. Over 18 months, and without therapy, she has remained healthy, and her lymphadenopathy significantly improved. No bone marrow or peripheral blood involvement was ever identified. Atypical T cells showed an immunophenotypic spectrum of T-cell antigen expression with partial CD33 on a subset of T cells detected by both flow cytometry and immunohistochemistry. Both T-cell clonality and Human Androgen Receptor Assay (HUMARA) studies, performed on lymph node biopsy specimens, were negative. This case represents the first detailed clinical, morphologic, molecular, and immunophenotypic description of disseminated multinodal involvement by nonclonal iT-LBP with partial CD33 expression on T cells.