Diagnostic Approach of Mycosis Fungoides and Unusual Benign Mimickers

Abstract

Background: Diagnosis of mycosis fungoides (MF) and its mimickers is a major diagnostic challenge in era of Dermatopathology. Objective: To draw a diagnostic stepwise approach to minimize this challenge focusing on the benign (unusual) mimickers of infectious etiology. Patients/methods: This retrospective study included 94 paraffin blocks of patients with clinical suspicious of MF or its mimickers, during the period from Jan 2019-July 2021. The hematoxylin and eosin (H&E) stained sections and their associated clinical presentations were reviewed. Ancillary studies were performed upon the preliminary clinical diagnosis of each case. Deeper serial sections with selected special stains were done for benign mimickers. Primary (CD3/CD4/CD7/CD68) and secondary (CD20/CD8/CD30) panels of immunohistochemistry (IHC) markers were performed for most of the cases. Results: A wide spectrum of MF mimickers was identified, our cases were categorized into 3 groups: the first is classic MF ( 24) and its variants (5), the second is benign mimickers [subgrouped into infectious (31) & non infectious (21)] and the third is heterogeneous group; (other lymphomas/parapsoriasis) (13). A suggested stepwise diagnostic approach with selected IHC panels characterizes each group. Conclusion:A constellation of diagnostic clinical data, diagnostic histopathological clues and the suggested stepwise approach minimize the misdiagnosis of classic MF and conclusively identify the infectious mimickers.