Linear unilateral hamartomatous basal cell naevus with glandular and follicular differentiation.

Mosaicisms are characterized by genetic or functional differences between > or = 2 cell lines in one person, derived from a single zygote. Of the various clinical patterns of cutaneous mosaicism, linear lesions following Blaschko's lines are probably the most commonly encountered, Several cases of multiple basal cell carcinomas or basaloid hamartomatous lesions distributed in a segmentary distribution and following Blaschko's lines have been described. The various terms of 'linear unilateral basal cell naevus with comedones', 'linear unilateral basaloid follicular hamartoma', 'linear unilateral basal cell naevus', and 'basal-cell and linear unilateral adnexal hamartoma' have been used to define this apparently heterogeneous group of disorders. We report a 66-year-old woman with a linear unilateral lesion that appeared during puberty and that histologically showed an adnexal hamartomatous lesion with multiple superficial and nodular basal cell carcinomas. Focal areas of glandular and follicular differentiation were also noted. Molecular studies from these lesions ruled out loss of heterozygosity or mutations in patched gene.