Diagnostic and prognostic significance of eccrinotropism in mycosis fungoides

Background: The differential diagnosis between an early-stage Mycosis Fungoides (MF) and dermatitis may be challenging. Eccrinotropism, the infiltration of eccrine glands by lymphocytes, has been reported in cases of both skin conditions. The aim of the study was to assess the diagnostic and prognostic meanings of eccrinotropism in early-stage MF. Methods: This retrospective study included 67 patients with histologically confirmed early-stage MF and 34 patients with chronic non-allergic idiopathic dermatitis. Histological and immunohistochemical analyses were conducted to assess the presence and intensity of eccrinotropism. Polymerase chain reaction (PCR) was used to evaluate clonal T-cell receptor (TCR) rearrangements in intraepidermal and eccrinotropic lymphocytes. Statistical analyses were performed to investigate the correlation between eccrinotropism and disease prognosis. Results: Eccrinotropism was identified in 71% of early-stage MF cases compared to 32% of dermatitis cases, with a statistically significant difference (P=0.008). Eccrinotropism ≥30% was correlated with early-stage MF and correlated with a relapsing-remitting clinical course (P=0.001). Phenotypic abnormalities and clonal TCR rearrangements were consistent between intraepidermal and eccrinotropic lymphocytes, confirming their shared malignant origin. Conclusions: Eccrinotropism is a valuable diagnostic feature distinguishing early-stage MF from dermatitis. Furthermore, a high degree of eccrinotropism correlates with a more severe, relapsing-remitting clinical course, underlining its prognostic importance. These findings support the inclusion of eccrinotropism as a diagnostic and prognostic marker in the clinical management of early-stage MF.