Nodular or clear cell hidradenoma denotes an asymptomatic, exceptional, gradually progressive, benign, solid or cystic, intra-dermal adnexal neoplasm of sweat gland origin with eccrine or apocrine differentiation. Initially scripted by Mayer in 1941, the tumefaction describes with a dual subtype as hidradenoma with eccrine or period differentiation and hidradenoma with apocrine or clear cell differentiation . Frequent betwixt fourth and eight-decade, peak incidence of the disorder is cogitated within sixth decade although clear cell hidradenoma can appear in the first decade. Of undetermined genesis, the cutaneous neoplasm arises from eccrine dermal adnexal glands although apocrine derivation is occasionally delineated. Clear cell hidradenoma or the nodular hidradenoma is a frequent histological subtype. The nomenclature includes captions such as eccrine acrospiroma, solid-cystic hidradenoma, clear cell acrospiroma, clear cell myoepithelioma, eccrine sweat gland adenoma, nodular hidradenoma, clear cell hidradenoma, cystic nodule hidradenoma, and eccrine acrospiroma.
Eccrine acrospiroma elucidates as a solitary, firm, nodule with a preferable localization in the head and neck, face and upper extremities although lesions can be cogitated on the chest, shoulder, upper torso, upper or lower extremities. A female to male ratio of 1.7 :1 and a mean age of presentation at 37.2 years is exemplified. An estimated proportion of lesions are cogitated at the head (30.3%), upper limb (25.8%) and trunk (20.2%) [2,3]. Paediatric adnexal tumours demonstrate a predominantly follicular or apocrine/ eccrine genesis. Pilomatrixoma is a frequent and most encountered skin adnexal tumefaction situated in head and neck region. Tumours with sebaceous differentiation are distinctly infrequent. Hidradenoma is generally elucidated betwixt 20 to 50 years of age. Clear cell hidradenoma can occur as a polypoidal umbilical mass, congenital neck swelling or as axillary nodules in infants. Hidradenoma emerge as a gradually progressive, solitary, asymptomatic, firm, mobile tumefaction or nodule [3,4]. A few of the tumour nodules can demonstrate a serous effluvium or may ulcerate. No anatomical site is exempt from the appearance of the tumour. Lesions are disclosed in vulva in females, peri-anal region inmales, scalp, head and neck, face, lower eyelid, external auditory canal, knee and foot. The tumefaction can be associated with hyper-oestrogenaemia as oestrogen and progesterone receptors are discerned on the tumour cells. Hyper-oestrogenaemia can engender multitudinous lesions at various sites [4,5].
Tumefaction of hidradenoma appears as solitary or multiple lesions. A female preponderance is noted with implication of middle-aged individuals. Adult females can exhibit lesions confined to the vulva. Although the disorder is predominantly cogitated in adults, nodular hidradenoma can arise in children. The nodules are frequently asymptomatic, evolve gradually and rarely demonstrate clinical symptoms such as pain and serous discharge. Solid or cystic, well demarcated, asymptomatic, minimally progressive, endophytic, rarely exophytic nodules of varying magnitude are cogitated usually of dimension betwixt 0.5 centimetres to 3.0 centimetres. The tumefaction enunciates a minimal possibility of malignant transformation and probable ulceration. The generally solitary nodules are skin coloured or crimson and frequently elucidated on the scalp, face, thorax, abdomen and proximal extremities [5,6]. Unconventional clinical appearance is cogently described with tumours exceeding 3 centimetres in diameter, erosion of the superficial surface, a preponderant cystic component and aberrant locations such as the plantar region.
Clear cell hidradenoma is a well circumscribed, un-encapsulated tumour as delineated on gross and morphological examination. Clear cell hidradenoma comprises of lobules of tumour cells situated in the dermis with extensions into subcutaneous fat. The tumefaction is segregated from the epidermis by a dormant Grenz zone. The neoplasm, characteristically confined to the upper dermis, demonstrates a congregation of dual population of miniscule or enlarged, monomorphic or polyhedral epithelial cells with copious clear or eosinophilic cytoplasm and miniature nuclei [6,7]. The dimorphic cell population elucidates polygonal cells with abundant glycogen thereby inducing a clear appearance to thecytoplasm admixed with elongated, darkly stained, miniature
cells cogitated at the periphery.
Clear cell metamorphosis and/or squamous metaplasia can
be a predominant feature within the tumour cell accumulates.
Focal apocrine elements are evidently displayed. The tumour
exhibits diverse composites and nodules of benign epithelial
cells articulating miniscule ductules and duct lumina generally
cogitated within the upper dermis. Duct like configurations
recapitulate the eccrine ducts. Additionally, slit like spaces lined
by concentric layer of squamous epithelial cells are exemplified.
Numerous cystic spaces are elucidated on account of tumour cell
degeneration. Apocrine secretion can be delineated within the
ductular lumen due to decapitation of cytoplasmic vacuoles [7,8].
Squamous, sebaceous or mucinous epithelial differentiation
can be enunciated in specific lesions. The cellular component
is variable, although clear cell predominance emerges in
proportionately one third instances. Distinctive lesions are
enveloped in an intact dermal integument or can demonstrate
focal and superficial ulceration with discharge of serous fluid.
The tumefaction exhibits singularly solid or cystic elements or an
admixture of solid and cystic components in varying proportions
or a clear cell predominance. Solid areas enunciate epithelial
lobules comprised of preponderant polyhedral cells with a
basophilic cytoplasm and clear cells with glycogen containing
cells with a clear cytoplasm. Clear cells contain glycogen or a
diastase resistant substance which stains with periodic acid
Schiff’s (PAS) reagent. Lipid vacuoles are not elucidated.
Clear cells denote a metabolic variant of epidermoid cells,
rather than an aberrant category of tumour differentiation.
Stroma intervening within the lobules enunciate delicate,vascularised cords of fibrous tissue or dense hyalinised tissue.
Myxoid and chondroid stroma are infrequent. Exophytic growth
with superficial surface erosion of the tumour is observed [8,9].
As the histological description and annotation is competent,
confirmation with immune histochemistry is not a cogent,
essential exercise. Malignant transformation is infrequent and
is characterized by morphological parameters such as nuclear
atypia, necrosis and atypical mitosis. A distinctive histological
enunciation may not accurately predict the clinical behaviour of
clear cell hidradenoma (Figure 1-14).
Clear cell hidradenoma necessitates a distinction from
a concordant lesion such as haemangioma, glomus tumour,
cutaneous lymphoma, dermatofibrosarcoma protuberans,
leiomyoma, follicular cyst, trichilemmoma or adjunctive sweat
gland or adnexal tumours which are clinically indistinguishable
[9,10]. Clear cell neoplasm confined to the dermis necessitate
a segregation from metastatic malignancies and primary
skin tumours with follicular, sebaceous and sweat gland
differentiation. Clear cell hidradenoma in adults require a
demarcation from metastatic renal cell carcinoma. However,
nodules of hidradenoma are devoid of the classic pulsating
vascular prominence as delineated in malignant deposits of
renal cell carcinoma [10,11]. Although clear cell hidradenoma,
also termed as eccrine acrospiroma, is predominantly a
benign neoplasm, the nodules can be subjected to malignant
transformation. Engendered malignancy is cogitated as “clear
cell hidradenocarcinoma” or “malignant clear cell hidradenoma”.
The malignant counterpart is an exceptional neoplasm and is
characterized by an infiltrative tumour perimeter, cellular atypia
and innumerable atypical mitosis [11,12].
A comprehensive surgical extermination is a pre-requisite
in managing clear cell hidradenoma as the nodules are
endowed with an enhanced potential of tumour recurrence. Awide tumour perimeter on surgical excision is mandated for
a detailed histological confirmation which ensures minimal
probable reoccurrence and evaluating prospective malignant
transformation. A surgical eradication of the neoplasm
with a broad perimeter is the preferred therapy. Malignant
transformation is infrequent although neoplasm such as
clear cell hidradenocarcinoma tend to reappear. Tumefaction
undergoing malignant conversion demonstrate an aggressive
clinical course, disseminated disease with adjuvant, enhanced