Pathology of Folliculosebaceous Cystic Hamartoma

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Dr Sampurna Roy MD 2022

Answer - Folliculosebaceous Cystic Hamartoma

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:

- 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 and 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.