Bulky naevocytoma of the perineum: a singular variant of congenital giant pigmented naevus.

We describe two instances of a previously unrecognized variant of congenital giant pigmented naevus (GPN), presenting as a bulky naevocytic tumour in the perineal region. In both cases the lesion was present at birth and attained massive dimensions. In addition to the characteristic histological patterns found in GPN, which included extensive areas with a neural appearance, these tumours presented an uncommon tendency to form pseudo-follicular structures lined by naevus cells. No features suggestive of malignant transformation were found. Because GPN may associate with an underlying malignancy, accurate diagnosis of this lesion is important in clinical practice.