1 Histopathologist, AB Diagnostics, New Delhi, India
Corresponding author details:
Anubha Bajaj
Histopathologist
AB Diagnostics
New Delhi,India
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 [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].
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.
Figure 7: Folliculosebaceous cystic hamartoma demonstrating
an admixture of epithelial and mesenchymal elements and a
preponderantly lobular architecture.
Figure 8: Folliculosebaceous cystic hamartoma exhibiting enlarged,
cystic arrangements with a squamous epithelial lining, adjacent
collagen bundles and sebaceous lobules with mild perivascular
infiltrate and absent hair follicles.
Folliculosebaceous cystic hamartoma requires a demarcation
from lesions such as sebaceous gland hyperplasia, steatocystoma,
nevus lipomatosus superficialisor a cutaneous dermoid cyst, whereas
the cystic hamartoma delineates an admixture of adipocytes and
fibrous stroma. Various papulo-nodular or cyst like cutaneous lesions
require segregation from folliculosebaceous cystic hamartoma [6,7].
Nevus sebaceous of Jadassohn demonstrates miniature, aberrant,
budding sebaceous glands appearing adjacent to hyperplastic,
stratified squamous epithelium with papillomatous articulations.
Sebaceous trichofolliculoma resembles folliculosebaceous cystic
hamartoma on morphological grounds although a distinction
is possible. Multiple, refractile, vellus hair shafts are cogitated
in sebaceous trichofolliculoma along with numerous sebaceous
lobules in the absence of a centric, cyst-like cavity. Characteristically,
mesenchymal stroma is absent in sebaceous trichofolliculoma
although proliferation of nerve fibres along with adjunctive
mesenchymal components can be enunciated [6,7]. Differentiation
betwixt folliculosebaceous cystic hamartoma and sebaceous
trichofolliculoma is challenging as the lesions primarily exemplify an
infundibular cyst with encompassing sebaceous lobules. However,
sebaceous trichofolliculoma depicts distinctive features such as
excavated lesions on clinical examination and emergence of hair
shafts within follicular structures. On the contrary, folliculosebaceous
cystic hamartoma is represented as papules or nodules and is
devoid of hair shafts within follicular structures [6,7]. Histological
manifestations of folliculosebaceous cystic hamartoma emerge
on account of secondary follicular regression encountered within
sebaceous trichofolliculoma and aforesaid lesion is considered asa
delayed phase of trichofolliculoma. Nevertheless, occurrence of
congenital folliculosebaceous cystic hamartoma remains unexplained.
Therefore, the lesions are contemplated to be composed of diverse
histo-genesis. Additionally, exclusion of congenital cutaneous lesions
is necessitated from folliculosebaceous cystic hamartoma [8,9].
A comprehensive, surgical extermination of the neoplasm with
a wide perimeter of uninvolved tissue is mandated. On further
monitoring, individuals are asymptomatic and devoid of reoccurrence
of the neoplasm [8,9].
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