Multiple Primary Melanoma Associated with CDKN2A Mutation-Case Report and Review of the Literature.

The CDKN2A gene remains understudied in melanoma compared to BRAF alterations. Inactivation of this tumor suppressor gene through homozygous deletions in the 9p21 chromosomal region leads to cellular proliferation and disrupts pro-apoptotic pathways. Genetic changes in CDKN2A are linked to multiple primary melanomas (MPM), with patients diagnosed with melanoma facing an elevated risk of developing additional primaries. We present the rare case of a 72-year-old Caucasian woman with nine metastasizing melanomas across diverse anatomical sites, posing a diagnostic challenge. Initial diagnosis in 2022 revealed ulcerated superficial spreading melanomas, progressing to intradermal and papillary dermal populations with neurotropism and angiotropism by early 2023. Lymph node metastases were identified, classifying the condition as pT3b N3b. Subsequent assessments in April 2023 revealed clinically suspicious melanocytic lesions diagnosed as intradermal and traumatized junctional nevi. In late 2023, cutaneous pigmented lesions and subcutaneous metastases were confirmed as nodular nevoid low-CSD multiple melanomas. Fluorescence in situ hybridization testing revealed homozygous CDKN2A deletion, necessitating close multidisciplinary collaboration for an optimized care plan for effective monitoring and intervention in this intricate clinical scenario. In summary, this case report highlights the diagnostic challenges of MPM in a single patient. Stressing the importance of immuno-histochemistry and CDKN2A genetic testing, our findings underscore the crucial role of these tools in accurately distinguishing malignant melanocytic proliferations from nevi and characterizing MPM cases.