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Folliculosebaceous cystic hamartoma (FSCH),  first described by Kimura et al in 1991, is a rare cutaneous hamartoma composed of dilated folliculosebaceous units associated with mesenchymal elements. Some authors have presented evidence suggesting that this lesion is very closely related to trichofolliculoma.

Clinical presentation:    Majority of lesions present as 0.5-1.5-cm papules or exophytic nodules. Lesions are usually rubbery to firm in consistency. Typically arise in adulthood but the giant variant appears to be congenital and enlarges during puberty.

Site:  Face or scalp, ear and upper back. 

Microscopic features:

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Lobular neoplasm ; large cystic structure lined by squamous epithelium similar to the infundibular epithelium ;  surrounded by multiple mature sebaceous lobules ;  rudimentary hair follicules may be present in the middle of the dermis ; the folliculosebaceous cystic structures are set in a fibrovascular stroma containing fat cells & neural tissue ; marked increase in reticular dermal collagen bundles and between sebaceous follicles ;  some areas resemble angiofibroma ; moderate perifollicular lymphocytic infiltrate.

Differential diagnosis:   

Sebaceous gland hyperplasia ;  Steatocystoma ; Nevus sebaceus of Jadassohn  ; Small aberrant sebaceous glands, budding in close association with a hyperplastic papillomatous epidermis ;  Sebaceous trichofolliculoma- Histopathologically , FSCH shares several similar features to sebaceous trichofolliculoma, but it is usually possible to differentiate these two tumours  ; Dermoid cyst of skin.
 

 Abstract:

Two cases of folliculosebaceous cystic hamartoma.Clin Exp Dermatol. 2006;31(1):68-70.

Folliculosebaceous cystic hamartoma arising within a port-wine stain. Clin Exp Dermatol. 2005;30(5):509-11.

Folliculosebaceous cystic hamartoma with hair shaft fragments.Eur J Dermatol. 2005;15(2):105-6

Giant nevus lipomatosus superficialis with multiple folliculosebaceous cystic hamartomas and dermoid cysts. J Eur Acad Dermatol Venereol. 2005;19(1):84-6.

Giant folliculosebaceous cystic hamartoma of the upper extremity. J Cutan Pathol. 2004;31(3):287-90.

Genital variant of folliculosebaceous cystic hamartoma. Dermatology. 1998;197(3):258-60.

Folliculosebaceous cystic hamartoma.Pathology. 1998;30(2):212-4.

Folliculosebaceous cystic hamartoma with a neural component: an immunohistochemical study. J Dermatol. 1997;24(7):451-7.

Folliculosebaceous cystic hamartoma: a clinical pathologic study. J Am Acad Dermatol. 1996;34(1):77-81.

Folliculosebaceous cystic hamartoma with perifollicular mucinosis. Am J Dermatopathol. 1996;18(1):58-62.

Giant folliculosebaceous cystic hamartoma. J Cutan Pathol 1994; 21 : 170-2.

Folliculosebaceous cystic hamartoma. Reported case with a neural component. Am J Dermatopathol 1993;15:277-9.

Folliculosebaceous cystic hamartoma associated with rosacea. J Dermatol. 1993;20(11):712-4.

Folliculosebaceous cystic hamartoma. A distinctive malformation of the skin. Am J Dermatopathol 1991;13:213-20.