SkIndia Quiz 41: Asymptomatic Skin-Colored Papule on the Scalp Skin.

A 33-year-old woman presented with an asymptomatic skin-colored papule with a central, outward woolly tuft, clinically appearing as white hair on the scalp skin. On physical examination, a 1 cm skin-colored papule with woolly hair tuft arising from the lesion was found on the hairy skin [Figure 1]. No radiological investigation was done. The patient had a 2-year history of lesion, and the length of the white woolly tuft hair was the same as the normal hair. The patient had no history of systemic diseases and no family history of skin diseases. There was also no history of any trauma. The papular hairy skin lesion was completely excised with woolly rope-like central hair. On histopathological analysis, dermis was unremarkable and epidermis showed dilated follicle with multiple hair follicles in different phases of maturation [Figure 2a and b].

Figure 1

On physical examination, a 1 cm skin-colored papule with woolly hair tuft arising from the lesion was found on the hairy skin

Figure 2

On histopathological analysis, dermis was unremarkable and epidermis showed dilated follicle with multiple hair follicles in different phases of maturation (H and E, ×40) (a). High power confirming the above features (H and E, ×100) (b)

Answer

Trichofolliculoma.

Discussion

Trichofolliculoma is a rare pilar tumor and intermediate in differentiation between a hair follicle nevus, which is simple hyperplasia of the hair follicle, and a trichoepithelioma, which lacks maturation of the hair follicle.[1]

It usually presents as a solitary nodule approximately 0.5 cm in diameter in the head and neck region with central umbilication and a tuft of fine hairs protruding from it.[12] Trichofolliculoma is mostly seen in the head and neck regions.[1] Although the exact etiology of trichofolliculoma remains unknown, it is considered to represent immature differentiation of pluripotent skin cells toward hair follicles.[2] Trichofolliculoma clinically presents as small-sized lesions ranging between 0.2.0.5 cm in diameter, which are often whitish-red pearly papules. In some cases, a central follicular ostium or punctum may be identifiable and a small wool-like tuft of hair may protrude from the surface.[3] The present case showed woolly hair tuft arising from the lesion.

A tuft of white vellus hairs yields a distinctive morphological appearance to trichofolliculoma.[1] Trichofolliculoma may affect individuals of any age, but it is mostly seen in adults.[2] It is not associated with family history or other systemic diseases and is not a component of a syndrome.[13] Trichofolliculoma has no distinguishing clinical features; therefore, it is commonly confused with other syndromes such as milium, hair follicle nevus, keratoacanthoma, trichoepithelioma, syringoma, epidermoid cyst, and basal cell carcinoma.[4] Trichofolliculoma can be distinguished from hair follicle nevus based on the pathological findings of a central cyst-like structure surrounded by a proliferation of hair follicles.[24]

Trichofolliculoma is mostly diagnosed with histopathological analysis.[5] Trichofolliculoma is histopathologically characterized by a central dilated infundibulum of a primary follicle and secondary follicles radiating from the infundibular wall of the primary follicle. The secondary follicles are often small sized and resemble vellus hair follicles, and the tumor may have little stroma or may be embedded in a fibrous orb.[45] Trichofolliculoma is a benign condition; however, a case with malignant transformation following perineural invasion has been reported.[5] Surgical excision is the treatment of choice for trichofolliculoma.[2] The prognosis of trichofolliculoma is often good but the lesion may lead to recurrence, though rarely.[3] The skin lesion of the presented case was completely excised. After 6-month follow-up, no recurrence was observed. This case is a classic case, though less commonly seen among appendageal tumors. Dermatologists should be aware of lesions with white vellus hairs in order to diagnose trichofolliculoma.