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.

内容摘要

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. 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. 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. Patients with SPTL presenting with extensive skin involvement (T3) have a higher risk of disease relapses and are more likely to develop HLH. Subcutaneous panniculitis‐like T‐cell lymphoma (SPTL) is a rare cutaneous lymphoma characterized by infiltration of subcutaneous adipose tissue by neoplastic cytotoxic T cells, clinically mimicking panniculitis. The World Health Organization–European Organization for Research and Treatment of Cancer classification of primary cutaneous lymphomas restricts SPTL to tumors with an αβ T‐cell receptor phenotype. In 2017, a Tumor–Node–Metastasis (TNM) classification system was introduced for primary cutaneous lymphomas, excluding mycosis fungoides and Sézary syndrome, to enable standardized anatomical assessment of disease extent. However, its prognostic relevance in SPTL has not been well established. This study assessed the clinical applicability and prognostic value of the T category of the TNM classification system and skin lesion characteristics in SPTL. Hemophagocytic lymphohistiocytosis (HLH) developed in 21% of patients. The TNM classification applied to SPTL and provided valuable prognostic insights. Although visceral and lymph node involvement rates during disease progression did not differ significantly among T categories, patients with higher T classification were more likely to develop HLH. T3 category (generalized skin involvement) was associated with significantly poorer relapse‐free survival (RFS) compared with the T1 (solitary lesion) and T2 (regional involvement) categories. Reduced RFS was also associated with lipoatrophy, HLH, and visceral/nodal involvement. Multivariable analysis identified HLH and T3 stage as independent predictors of poor RFS. These findings suggest that the extent of skin involvement, as reflected by the T category, may predict the risk of HLH and disease recurrence. Incorporating the T category into clinical decision‐making may help optimize treatment intensity and duration in SPTL management.