A Case of Localized Follicular Hamartoma: An Ultrastructural and Immunohistochemical Study
April 2000
in “
Journal of Cutaneous Pathology
”
localized follicular hamartoma nevoid plaque squamoid cells basaloid cells interfollicular epidermis upper hair follicles keratin expression infundibular epithelium S-100-positive cells Factor XIIIa-positive dendritic cells immature melanocytes Merkel cells stromal dendritic cells cytoplasmic processes anchoring fibrils basal lamina secondary hair germs
TLDR The hamartoma is an abnormal hair growth with limited development in the upper hair follicle.
The document reported a case of a 22-year-old woman with a nevoid plaque termed localized follicular hamartoma, which appeared at puberty on one side of her face and scalp. The plaque consisted of numerous skin-colored to light brown papules, sometimes with a single hair. Histological examination revealed branched epithelial nests of squamoid and/or basaloid cells connected to the interfollicular epidermis and upper portions of hair follicles, with normal lower follicle structures. Immunohistochemical analysis showed keratin expression similar to infundibular epithelium, with S-100-positive cells in the nests and stroma, and numerous Factor XIIIa-positive dendritic cells near the nests. Ultrastructural analysis identified immature melanocytes and Merkel cells in the nests, and stromal dendritic cells with cytoplasmic processes adhering to anchoring fibrils or basal lamina. The findings suggested the hamartoma was an abortive growth of secondary hair germs with limited differentiation to the upper follicular portion.
