The Adnexal Malformation-folliculosebaceous Cystic Hamartoma

Anubha Bajaj1*

1 Histopathologist, AB Diagnostics, New Delhi, India

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Anubha B. The Adnexal Malformationfolliculosebaceous Cystic Hamartoma. Biomed Res Rev. 2020 Feb;3(2):121


Folliculosebaceous Cystic Hamartoma (FSCH) was initially scripted by Kimura et al in 1991 and is cogitated as an exceptional, non neoplastic, cutaneous adnexal malformation comprised of distended follicular and sebaceous glandular unitsoccurring in association with mesenchymal elements [1]. Nomenclature of folliculosebaceous cystic hamartoma emerges from cogent histological features comprised of follicular, cystic articulations appearing with adjacent, multiple sebaceous lobules accompanied with modifications of mesenchymal stroma. Folliculosebaceous cystic hamartoma requires a segregation from asymptomatic, flesh coloured nodules or papules, particularly when originating within the face and scalp [1].  

Disease Characteristics

Folliculosebaceous cystic hamartoma is an infrequent, benign, cutaneous, nodular neoplasm essentially arising from the hair follicle. On account the multitudinous, mature, ectodermal articulations and an admixture of mesodermal elements, the neoplasm is cogitated as a hamartoma or can be contemplated asan extension of or akin to sebaceous trichofolliculoma. Folliculosebaceous cystic hamartoma demonstrates a female preponderance, emerges in adulthood and progresses gradually. Folliculosebaceous cystic hamartoma is commonly exhibited betwixt 4 years to 84 years and exemplifies a mean age of occurrence at 51 years while the neoplasm is infrequent in infants beneath < one year [2,3]. Folliculosebaceous cystic hamartoma can concur with neurofibromatosis and the tumefaction can be misinterpreted as neurofibroma. Giant folliculosebaceous cystic hamartoma can arise as a congenital lesion or appears in infants, enlarges within the pubertal phase and is frequently discerned upon the face or adjunctive areas [2,3].

Clinical Elucidation

Folliculosebaceous cystic hamartoma enunciates nodules which are commonly situated upon the head, scalp,earlobe, superior dorsal region, posterior thigh, genital region, nose whereas centric region of the faceis a frequent location. An estimated 30% lesions arise within the nasal and paranasal region. Uncommonly, lesions on the scrotum and nipple can be discerned [2,3]. Majority of lesions are configured as solitary, rubbery, firm or soft, flesh coloured, sessile or pedunculated, polyps, papules or exophytic nodules with a smooth exterior and an adherence to the superimposed cutaneous surface. The magnitude usually varies from 0.5 centimetre to 1.5 centimetre whereas the dimensions generally beneath < 3 centimetres. The superficial cutaneous surface demonstrates multiple nodules admixed with scattered, distended pores exuding a viscous, oily discharge. Clinical segregation from various, benign cutaneous tumours such as a sessile papilloma, intradermal nevi, sebaceous hyperplasia, lipoma, dermoid cyst and neurofibroma is mandated [2,3].  

Histological Elucidation

On gross examination, a flesh coloured or pinkish white, pedunculated or sessile nodule of variable diameter is exemplified which elevates the superimposed epidermis. Cut surface demonstrates multiple cysts impacted with whitish yellow substance. The neoplasm can be appropriately categorized as a hamartoma upon a cogent histological examination. Diagnostic morphological features of folliculosebaceous cystic hamartoma are delineated as sebaceous lobules adherent to infundibular cystic articulations, circumscribed with bundles of collagen, an admixture of mature adipocytes and an augmentation of miniature venules with a superimposed hyperkeratotic, acanthotic, stratified squamous epithelial lining [4,5]. The dermal region depicts multiple, distended pilo-sebaceous units delineating an infundibular variety of keratinization along with enunciation of several, radiating sebaceous lobules. Aforesaid cystic follicular arrangements are enveloped by mesenchymal tissue. Enhancement of muscular element abutting the sebaceous lobules is exemplified. Secondary hair follicles are absent. Folliculo-cystic configurations are surrounded by dense aggregates and bundles of laminated collagen admixed with abundant adipose tissue and an accompaniment of vascular proliferation [4,5]. The neoplasm is predominantly lobular and articulated, enlarged cystic structures are preponderantly layered by mature, stratified squamous epithelium, identical to the infundibular epithelium. Multiple, mature sebaceous lobules appear circumscribed. Rudimentary hair follicles can be discerned within the mid-centric dermis. Folliculo-sebaceous cystic structures encompassed within the fibro-vascular stroma demonstrate aggregates of adipose tissue cells and elements of neural tissue. Collagen bundles configured within the reticular dermis are preponderantly enhanced and appear amidst sebaceous follicles. Foci which recapitulate angio-fibromas can be observed. A moderately disseminated perifollicular lymphocytic infiltrate is delineated [4,5]. The well circumscribed, dermal lesion is comprised of numerous follicular articulations and sebaceous lobules accompanied by distended, cystic spaces which directly extend to the superficial epidermis. The epithelial articulations are circumscribed by a fibro-hyaline stroma in concurrence with a fibrous component demonstrating an admixture of adipocytes [4,5] (Figures 1-8).

Figure 1: Folliculosebaceous cystic hamartoma demonstrating a lobular architecture with squamous epithelium lined cystic spaces and surrounding bundles of collagen.

Figure 2: Folliculosebaceous cystic hamartoma with radiating cords and cystic spaces lined with stratified squamous epithelium and an enveloping stroma of fibro-vascular tissue and sebaceous lobules.

Figure 3: Folliculosebaceous cystic hamartoma depicting variously sized, epithelium lined cystic spaces, a circumscribing fibrous tissue stroma, a mild perivascular lymphocytic infiltrate and an absence of secondary hair follicles. 

Figure 4: Folliculosebaceous cystic hamartoma delineating lobules of epithelium lined cystic spaces, encompassing fibrous tissue stroma, occasional sebaceous lobule and a mild, perivascular lymphocytic infiltrate

Figure 5: Folliculosebaceous cystic hamartoma with a lobular array of epithelium lined cystic architecture surrounded by bundles of collagen, scant inflammatory exudate and rudimentary hair follicles.

Figure 6: Folliculosebaceous cystic hamartoma with epithelium layered cystic spaces of varying magnitude, abutting sebaceous lobules and an admixture of collagenous tissue.