Folliculocystic and Collagen Hamartoma: A Distinct Hamartoma Associated With Tuberous Sclerosis Complex

Histological Patterns of Skin Lesions in Tuberous Sclerosis Complex: A Panorama

Tuberous Sclerosis Complex (TSC) is a multisystem genetic disease characterized by cutaneous and extracutaneous hamartomas. The diagnosis is based on the association of major and minor criteria, defined by a consensus conference updated in 2012. The clinical examination of the skin is crucial because seven diagnostic criteria are dermatological: four major (hypomelanotic macules, angiofibroma or fibrous cephalic plaques, ungual fibromas, shagreen patches) and three minor criteria (confetti skin lesions, dental enamel pits, intraoral fibromas). Skin biopsy is commonly performed to assert the diagnosis of TSC when the clinical aspect is atypical. Histopathology of TSC cutaneous lesions have been poorly reported until now. In this article, we review the histologic features described in the literature and share our experience of TSC skin biopsies in our pediatric hospital specialized in genetic disorders. Both hypomelanotic lesions and cutaneous hamartomas (angiofibroma/fibrous cephalic plaques, ungual fibromas, shagreen patches) are discussed, including the recent entity called folliculocystic and collagen hamartoma, with a special emphasis on helpful clues for TSC in such lesions.

Folliculocystic and Collagen Hamartoma: A Subset of Fibrous Cephalic Plaque

Tuberous sclerosis complex is known to cause a variety of cutaneous hamartomas, most commonly hypomelanotic macules, angiofibromas, shagreen patches, and fibrous cephalic plaques. In recent years, a new cutaneous hamartoma that bears physical and histological resemblance to fibrous cephalic plaque has been proposed called folliculocystic and collagen hamartoma. The primary difference between the two diagnoses is the histologic presence of infundibular cysts in the latter. However, some authors have called into question if the two diagnoses are truly distinct. In this case report, we present a patient with tuberous sclerosis complex and fibrous cephalic plaque with infundibular cysts and propose that the presence of cysts should be incorporated into the possible histologic features of fibrous cephalic plaque.

Miliary fibromas in tuberous sclerosis complex

BACKGROUND

Tuberous sclerosis complex (TSC) is a hamartoma syndrome characterized by multiple skin lesions, such as angiofibromas, shagreen patch and miliary fibromas (MiF).

OBJECTIVE

To determine the clinical and histological features of MiF.

METHODS

A retrospective analysis was conducted on 133 adults with TSC. Photography was used to characterize the appearance and location of MiF. Histological features in five skin samples from four individuals were evaluated by a board-certified dermatopathologist.

RESULTS

MiF were observed in 19 of 133 (14%) individuals with TSC. MiF were 1- to 3-mm skin-coloured, sessile papules scattered on the back and rarely buttocks or thighs. Most were scattered in a bilaterally symmetric distribution, but others were asymmetric or associated with a shagreen patch. Histological features of MiF included expansion of the papillary and periadnexal dermis with variable hamartomatous abnormalities involving adjacent epithelial components.

CONCLUSIONS

MiF are distinct from other cutaneous lesions in TSC such as shagreen patches and angiofibromas. Recognition of this entity is important in defining the spectrum of TSC disease and reassuring individuals with TSC that these lesions are benign.