Melanogenesis and MITF expression in primary melanomas: an immunohistochemical study

The Microphthalmia-associated transcription factor - MITF is a key regulator of melanogenesis, controlling melanin production and pigment phenotype in melanocytes. It also influences cell differentiation, proliferation, and survival. In melanoma, MITF immunohistochemical expression varies among tumor subpopulations, with reduced expression typically associated with less differentiation phenotype and increased invasive potential. This study aimed to assess the relationship between MITF immunohistochemical expression and melanoma pigmentation. In order to assess the association of MITF expression with pigmentation, we conducted a cross-sectional study involving 91 cases of primary cutaneous melanoma. Immunohistochemical expression of MITF (H-score > 5) was detected in 86 out of 91 primary melanomas (94.5%). A significant association was found between MITF expression and tumor pigmentation (p = 0.007). Among the five MITF-negative cases, three were desmoplastic and two were nodular melanomas. MITF is expressed in the vast majority of primary melanomas and shows a significant association with tumor pigmentation. These findings support the role of MITF as a key marker of melanocytic differentiation and reinforce its relevance in the phenotypic characterization of melanoma.