Histologic features of melanoma associated with germline mutations of CDKN2A, CDK4, and POT1 in melanoma-prone families from the United States, Italy, and Spain.

Background: CDKN2A, CDK4, and POT1 are well-established melanoma-susceptibility genes.

Objective: We evaluated melanoma histopathology for individuals with germline mutations of CDKN2A, CDK4, and POT1.

Methods: We assessed histopathology for melanomas diagnosed in melanoma-prone families (≥2 individuals with melanoma) from the United States, Italy, and Spain. Comparisons between mutation carriers and noncarriers (no mutation) were adjusted for age, sex, Breslow depth, and correlations among individuals within the same family.

Results: Histologic slides were evaluated for 290 melanomas (139 from 132 noncarriers, 122 from 68 CDKN2A carriers, 10 from 6 CDK4 carriers, and 19 from 16 POT1 carriers). Superficial spreading was the predominant subtype for all groups. Spitzoid morphology (>25% of tumor) was observed in 10 of 15 invasive melanomas (67%) from POT1 carriers (P < .0001 vs noncarriers). This finding was independently confirmed by 3 expert melanoma dermatopathologists in 9 of 15 invasive melanomas (60%). In situ and invasive melanomas from CDKN2A and CDK4 carriers were histologically similar to melanomas from noncarriers.

Limitations: Limited sample sizes for rare melanoma-susceptibility syndromes (CDK4, POT1).

Conclusion: Spitzoid morphology was associated with POT1 mutations suggesting that telomere dysfunction (POT1 mutations) may contribute to spitzoid differentiation in melanocytic tumors.