The Presence of Pigment Incontinence in Sinonasal Mucosal Melanoma.

Background: Regression is an immunological phenomenon described in cutaneous melanoma whereby tumor is replaced with tumor-infiltrating lymphocytes, granulation tissue, and mature fibroblasts often accompanied by pigment incontinence (accumulation of melanin in the upper dermis). Pigment incontinence results in grossly pigmented lesions that may be mistaken for viable tumor and has not been described in sinonasal mucosal melanoma (SNMM). This study investigates the presence of regression and pigment incontinence in patients with SNMM.

Methods: A retrospective chart review was conducted on SNMM patients from 2007 to 2023. Pathology slides from surgical resection were examined by two pathologists blinded to treatment information for the presence and extent of pigment-laden macrophages and other histopathologic features of regression.

Results: Seventeen patients with SNMM were included in this study who underwent surgical resection. Three patients received neoadjuvant therapy followed by surgical resection. Regression was present in 94% of patients and pigment incontinence was present in 65% of patients and occurred in both neoadjuvant treated patients and treatment naïve patients. All three patients with neoadjuvant treatment had evidence of pigment incontinence.

Discussion: This study highlights that SNMM often displays characteristics of regression. This study is one of the first to describe the presence of pigment incontinence in patients with SNMM. Pigment incontinence can be a part of the natural tumor life cycle and grossly pigmented lesions could easily be confused for melanoma especially after neoadjuvant therapy. Developing an understanding of regression and pigment incontinence within SNMM is important for diagnosis and clinical management.

Level of evidence: IV Laryngoscope, 2024.