Nodular melanoma, light micrograph. Nodular melanoma (NM) accounts for 3-4% of all melanoma cases. It occurs in a relatively younger age group (5th or 6th decades) than other melanoma subtypes and is of shorter duration. It appears as a smooth firm elevated nodule or a polypoid mass covered by epidermis. The colour ranges from tan (amelanotic variants), brown, blue to black. The atypical melanocytes are arranged in sheets or infiltrating nests and show moderate cytologic atypia. Several of them contain brown melanin pigment.