Histopathological Characterization and Development of Objective Diagnostic Criteria in Mycosis Fungoides

Background: Mycosis Fungoides is a subtype of Cutaneous T Cell Lymphomas, often difficult to diagnose in its early stages due to its histopathological resemblance to inflammatory dermatoses. Objectives: To refine and enhance the diagnostic criteria for Mycosis Fungoides by utilizing digital scanning and analysis systems for the quantitative evaluation of immunohistochemical markers. Methods: A retrospective longitudinal observational descriptive study based on the reevaluation and comparison of diagnostic criteria (histological and immunohistochemical) of patients with a clinical suspicion of MF, creating two groups: patients whose diagnosis, despite requiring numerous biopsies, was finally Mycosis Fungoides (MF Group), and patients who, despite clinical suspicion, always had a diagnosis of Inflammatory Dermatoses (Control Group). The study was conducted on 62 patients with clinical suspicion of MF who underwent punch biopsies between 2000 and 2022 at Severo Ochoa University Hospital. Histological and immunohistochemical markers (CD2, CD3, CD4, CD5, CD7, CD8, TOX) were assessed using APERIO AT2 LEICA BIOSYSTEMS scanner and CIVAGENIUS software, ensuring objective and reproducible results. Results: Basal epidermotropism, lymphocytic atypia, and peri-lymphocytic halo showed strong associations with MF diagnosis. Significant differences were observed in the CD3/CD8 and CD5/CD8 ratios between Mycosis Fungoides and Inflammatory Dermatoses groups. High TOX antibody expression correlated with early-stage MF diagnosis. These findings suggest the potential of combining marker ratios and TOX expression with digital analysis to improve diagnostic accuracy. Conclusions: Digital scanning and automated analysis systems significantly enhance the precision and efficiency of Mycosis Fungoides diagnosis. Implementing these methods in routine practice can reduce diagnostic delays and improve patient outcomes by differentiating Mycosis Fungoides from similar dermatological conditions more effectively.