Diagnostic spectrum of nodular melanoma

Nodular melanoma represents 10 to 30% of all melanomas and circa 50% of those with a Breslow thickness greater than 2 mm. The main cause of death among malignant cutaneous tumors, it pre- sents a high metastatic potential even in the early growth stages, making an early diagnosis funda- mental. It is more common in men than in women, its onset is in later age, in any part of the body, more often on the neck and head. Due to its clinical characteristics (symmetrical, nodular, amelanotic/hypomelanotic or highly pig- mented lesion) nodular melanoma is difficult to diagnose with the ABCD rule (Asymmetry, irregu- lar Borders, Color variation and Diameter). For this reason it is preferred to use the EFG rule which takes into consideration Elevation, Firmness and rapid Growth pattern. Histologically, nodular melanoma is characterized by the lacking of atypical melanocytes in the epi- dermis (up to 3 crests) beyond the lateral margins of the malignant dermal cellular component, with theca cells and/or confluent aggregates without maturation phenomena. The dermoscopic structures mainly related to nodular melanoma are asymmetry of the pigmen- tation pattern, blue-white veil, blue-black areas, milky red areas, irregular dots and globules, atyp- ical vascular pattern. Recently reflectance confocal microscopy has permitted a close dermoscopic-confocal correla- tion of melanocytic and non-melanocytic skin lesions. RCM features of nodular melanoma show atrophic or thin epidermis, sheet-like struc- tures at the dermo-epidermal junction and the presence of single or variable-in-size clusters of atypical melanocytes in the upper dermis in prox- imity or overlapping enlarged and convoluted vessels. In the diagnostic challenge of nodular melanoma, integration between clinical parameters and non- invasive skin techniques are needed to warranty a correct evaluation of pigmented, hypopigmented or achromic nodular lesion.