Comprehensive review of morphological diagnosis of adult T-cell leukemia-lymphoma

Abstract

Introduction: Adult T-cell leukemia-lymphoma (ATL) is a rare hematological malignancy associated with human T-cell leukemia virus type 1 (HTLV-1) infection. Accurate diagnosis and classification of ATL clinical subtypes rely on the identification of abnormal lymphocytes in peripheral blood smears. However, the diverse morphology of ATL cells and lack of standardized evaluation criteria worldwide can pose challenges.

Area covered: This review consolidates expert opinions from clinical laboratory technologists experienced in the diagnosis of ATL. Here, we present the characteristic features of ATL cells and the common pitfalls encountered in clinical practice. In acute-type ATL, the 'flower cell' with its deeply lobulated, petal-like nucleus is a hallmark feature. While highly diagnostic, flower cells may not be abundant in all samples, and cells with minimal nuclear atypia can coexist. Chronic-type ATL is often characterized by small ATL cells with nuclear indentations or twists and hyperchromatic chromatin. Smoldering-type ATL cells share a similar morphology but generally exhibit milder nuclear atypia.

Expert opinion: This review would facilitate the identification of ATL cells in routine clinical practice and serves as a foundation for future discussion and standardization of morphological criteria for ATL diagnosis.

Keywords: ATL cell criteria; Adult T-cell leukemia-lymphoma; Shimoyama’s criteria; comparative analogy; morphological diagnosis.