Basement membrane thickness helps to differentiate hypopigmented mycosis fungoides from clinical and pathological mimickers.

Abstract

Hypopigmented mycosis fungoides (HMF) is a relatively rare subtype of mycosis fungoides (MF). The diagnosis of HMF can be quite challenging in case of insufficient diagnostic criteria due to the diverse conditions that present with hypopigmented lesions. This study aimed to evaluate the usefulness of the assessment of the basement membrane thickness (BMT) in the diagnosis of HMF. A retrospective study was conducted on biopsy specimens of 21 HMF and 25 non-HMF cases who presented with hypopigmented lesions. The thickness of the basement membrane was evaluated in periodic acid-Schiff (PAS)-stained sections. The mean BMT was significantly higher in the HMF group than in the non-HMF group (P < 0.001). The best cut-off value of mean BMT for the detection of HMF verified in ROC analysis was 32.7 μm (P < 0.001) with a sensitivity of 85.7% and a specificity of 96%. Evaluation of BMT can be a useful tool to distinguish HMF from other causes of hypopigmented lesions in doubtful cases. We suggest the use of " BMT more than 33 μm" as a histopathologic criterion of HMF.