A case of unilateral, systematized linear hair follicle nevi associated with epidermal nevus-like lesions

Hair Follicle Nevus With Features of Comedo Nevus: An Expanding Spectrum

Hair follicle nevus (HFN) is a rare hamartomatous lesion of the folliculosebaceous unit, with or without admixed fibroadipose or muscular tissue. It typically has a congenital presentation in the preauricular area of infants and is frequently confused with an accessory tragus. Acquired tumors with similar histopathologic features have been described infrequently during adolescence and adult life. We report yet another unique presentation of this unusual lesion in a 4-year-old girl who had a long-standing tumor of the nasal columella that started growing rapidly after trauma. Histopathologic examination revealed increased numbers of hair follicles, some of which were associated with diminutive sebaceous glands, with no associated central cystic structure. In addition, the infundibula of the follicles were dilated and filled with keratinous debris. Although these hamartomas are common in the head and neck region, to our knowledge, this is the first report of a HFN at this anatomic location. In addition, this tumor has an overall architecture of a HFN but is accompanied by features of a comedo nevus. We also present a review of the literature and summarize the current diagnostic criteria for HFN.

Hair follicle nevus in a 2-year old

We report a 2-year-old boy with an elastic soft, flatly elevated, skin-colored nodule on his nasal ala. Histologic examination revealed numerous small hair follicles in several stages of maturation in the dermis. Serial sections did not show any cartilage or a central epithelial lined cystic structure. Based on clinico-pathologic findings, we diagnosed this lesion as a hair follicle nevus. Hair follicle nevus is quite rare. Histologically, it is very important not to find cartilage or a central epithelial lined cystic structure for distinction from an accessory auricle and from a trichofolliculoma, respectively. Awareness of the clinical and pathologic characterization of hair follicle nevus is an aid to a correct diagnosis.

Multiple Myofibromas and an Epidermal Verrucous Nevus in a Child with Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is a common neurocutaneous autosomal dominant genetic disorder affecting primarily tissues derived from the embryonic neural crest. Two hallmark features of NF1 are the wide range of potentially affected tissues and the enormous phenotypic variability of disease traits even among patients from the same family. We present a boy fulfilling the diagnostic criteria for NF1 with two unusual lesions: infantile myofibromatosis and a verrucous epidermal nevus. To our knowledge this association has never been described before.