Occurrence of ocular melanoma thirteen years after skin melanoma: two separate primaries or metastatic disease? A case solved with NRAS and CDKN2A (INK4A-ARF) mutational analysis

The differential diagnosis between primary uveal melanoma and cutaneous melanoma metastasis in the eye may be difficult, both clinically and histologically. We report successful application of combined mutational analysis of the NRAS and the CDKN2A gene to discriminate between these two entities. The patient had a history of a superficial spreading cutaneous melanoma of the left shoulder. Nine years later, she developed a lymph node metastasis in the left axilla, and 13 years later she presented with an atypical, pigmented tumor in the uvea. Histologically, the origin of the uveal melanoma could not be determined with certainty. We performed molecular analysis on the skin melanoma, the lymph node metastasis and the uveal melanoma. We detected an NRAS codon 61 mutation (c.182A>G, p.Gln61Arg) in all three tumor specimens. This mutation was absent in the normal control tissue of the patient, thereby excluding a germline mutation. To confirm a clonal relationship between the tumors, we also performed CDKN2A mutational analysis. We detected a CDKN2A mutation ((p16) c.238C>T, p.Arg80X, (p14) c.404C>T, p.Pro135Leu)) in the tumor samples, but not in the normal control tissue of the patient. We concluded that the uveal melanoma is a metastasis from the cutaneous melanoma removed 13 years before.