1 Histopathologist, AB Diagnostics, New Delhi, India
Corresponding author details:
Copyright: © 2020 Anubha B. This is an openaccess article distributed under the terms of the Creative Commons Attribution 4.0 international License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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 . 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 .
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].
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].
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.