Concept
Dysplastic nevus syndrome, also known as familial atypical multiple mole–melanoma (FAMMM) syndrome, is an inherited cutaneous condition described in certain families, and characterized by unusual nevi and multiple inherited melanomas. First described in 1820, the condition is inherited in an autosomal dominant pattern, and caused by mutations in the CDKN2A gene. In addition to melanoma, individuals with the condition are at increased risk for pancreatic cancer. The diagnosis of dysplastic nevus syndrome is based on clinical presentation and family history. Treatment consists of resection of malignant skin lesions (melanoma). Screening for pancreatic cancer may be considered, particularly if there is a family history. Dysplastic nevus syndrome is characterized by unusual nevi and multiple inherited melanomas. List of genes mutated in pigmented cutaneous lesions The CDKN2A gene is located on chromosome 9p21.3. Two main transcripts, isoforms '1' and '4', each contain three exons and span 7288 and 26740 bp, respectively. They encode proteins of 156 and 173 amino acids; isoform '1' encodes p16(INK4a), while isoform '4' encodes p14(ARF), a protein that is structurally unrelated to p16(INK4) but acts in cell cycle G1 control by stabilizing the tumor suppressor protein p53. Dysplastic nevus syndrome is inherited in an autosomal dominant manner. The penetrance for melanoma in kindreds with CDKN2A mutations is estimated at 58% to 92% by 80 years of age and varies with geography. The penetrance in CDKN2A mutation carriers for pancreatic cancer has been estimated to be 17% by 75 years of age. As noted above, there is wide variation in published estimates of the penetrance of CDKN2A mutations. The histopathologic characteristics of melanoma in FAMMM kindreds are not different from those seen in sporadic cases of melanoma and, thus, are not useful in diagnosing the syndrome. Superficial spreading melanoma (SSM) and nodular melanoma are the most frequently encountered histological melanoma subtypes in patients with CDKN2A mutations, which is consistent with the relative early age of onset.
