Prognostic Significance of <scp>TBX21</scp> and <scp>GATA3</scp> Subtype Classification in Indolent Adult T‐Cell Leukemia‐Lymphoma With Cutaneous Lesions

Chronic-type adult T-cell leukemia-lymphoma (ATL) without unfavorable prognostic factors and smoldering-type ATL are classified as indolent ATL. Indolent ATL patients often present with cutaneous lesions, but their clinical course is diverse. Smoldering-type ATL presenting with tumoral cutaneous lesions and without lung involvement has a poor prognosis and is designated as primary cutaneous tumoral (PCT) type. Indolent ATL prognostic index (iATL-PI) based on the soluble IL-2 receptor levels and its modified version have been proposed. Peripheral T-cell lymphoma, not otherwise specified (PTCL NOS) is classified into two prognostic subtypes, PTCL-TBX21 and PTCL-GATA3, using an immunohistochemistry (IHC) algorithm based on TBX21/CXCR3 and GATA3/CCR4 expression. Although ATL can also be classified into TBX21 and GATA3 subtypes, the prognostic significance of this classification in ATL remains unclear. To evaluate the prognostic significance of the IHC-based classification of TBX21 and GATA3 subtypes in indolent ATL with cutaneous lesions, we performed a single-center, retrospective cohort study involving 47 patients with indolent ATL with cutaneous lesions. We estimated survival according to the patients' characteristics, including the IHC subtype, and assessed their prognostic significance. Patients with GATA3 subtype showed significantly worse survival than those with TBX21 subtype. In multivariate analyses, GATA3 subtype was identified as an independent prognostic factor for overall survival, along with older age, PCT type, and modified iATL-PI. GATA3 subtype was also independently associated with poorer progression-free survival, in addition to PCT type and modified iATL-PI. These results indicate that the IHC-based classification into TBX21 and GATA3 subtypes is useful for predicting survival and progression in indolent ATL patients with cutaneous lesions.