Prognostic Value of Skin Lesion Characteristics in Subcutaneous Panniculitis‐Like T‐Cell Lymphoma: A Retrospective Cohort Study Assessing the Applicability of T Category of the TNM Classification for Primary Cutaneous Lymphomas Other Than Mycosis Fungoides and Sézary Syndrome

BACKGROUND: Subcutaneous panniculitis-like T-cell lymphoma (SPTL) is a rare form of cutaneous lymphoma characterized by neoplastic T-cell infiltration of subcutaneous tissue, clinically mimicking panniculitis. This study aimed to evaluate the applicability and prognostic value of the T component of the Tumor-Node-Metastasis (TNM) classification system, as well as the prognostic significance of skin lesion characteristics in patients with SPTL. METHODS: Clinical characteristics and survival outcomes of patients with SPTL treated at a Korean academic medical center were retrospectively reviewed to assess the prognostic significance of TNM T staging and skin lesion features. RESULTS: Among 43 patients with SPTL, nine had concurrent hemophagocytic lymphohistiocytosis (HLH). Higher T categories were associated with an increased likelihood of HLH. Although overall survival (OS) did not differ significantly across T categories, higher T stage and presence of lipoatrophy correlated with poorer relapse-free survival (RFS). Of all clinical variables, only HLH was significantly associated with reduced OS. Decreased RFS was associated with lipoatrophy, HLH, and visceral or nodal involvement. Multivariable analysis identified T3 stage and HLH as independent prognostic factors of RFS. CONCLUSIONS: Patients with SPTL presenting with extensive skin involvement (T3) have a higher risk of disease relapses and are more likely to develop HLH.