Trichilemmal carcinoma is an exceptional, malignant cutaneous adnexal neoplasm derived from extraneous root sheath of the hair follicle. The external hair follicular root sheath is comprised of clear cells with vacuolated cytoplasm and abundant intracellular glycogen. Trichilemmal carcinoma was initially scripted by Headington as a “historically invasive, atypical clear cell neoplasm of adnexal keratinocytes contiguous with superimposed epidermis and/or follicular epithelium” . Trichilemmal carcinoma is discerned upon cogent histopathological examination with complementary and confirmatory immune histochemical reactions [1,2].
As a malignant version of trichilemmoma, trichilemmal carcinoma demonstrates a predilection for sun exposed, hair bearing cutaneous surfaces. Trichilemmal carcinoma as a cutaneous adnexal tumour exemplifies a lesion distribution within zones of sunlight exposure or a concomitant appendageal origin and occurs predominantly upon the head and neck region [1,2]. Apart from distribution of lesions upon regions of sunlight exposure, trichilemmal carcinoma appears in burn scars or elderly subjects subjected to radiography for discernment of pulmonary lesions such as tuberculosis. Nevertheless, pathogenesis of trichilemmal carcinoma remains poorly explained [1,2]. A recent, abrupt stage of tumour growth is encountered within a phase of delayed tumour progression. Despite an aggressive pattern of tumour evolution, trichilemmal carcinoma delineates an indolent clinical course, which is primarily indicative of a benign neoplastic process, amenable to comprehensive surgical excision [2,3]. Trichilemmal carcinoma demonstrates a minimal metastatic potential, deep-seated tumour infiltration and occasional localized reoccurrence of the tumefaction, although the neoplasm is devoid of distant metastasis. Localized cervical or regional lymph node metastasis and distant metastasis are infrequently encountered in trichilemmal carcinoma. As investigative modalities for discerning trichilemmal carcinoma are inadequately denominated, biological behaviour and prognostic outcomes are challenging to predict . Metastatic trichilemmal carcinoma is associated with an inferior prognosis. Possible emergence of tumour reoccurrence and lymph node metastasis can be proportionate to aforesaid manifestations
of squamous cell carcinoma. Median follow up of trichilemmal carcinoma usually is 63.8 months and varies from one month to 147 months. On account of exceptional nature of the neoplasm, significant data is unavailable [3,4].
Trichilemmal carcinoma arises as a solitary, indolent neoplasm although multiple lesion can emerge upon non-exposed cutaneous surfaces. Trichilemmal carcinoma is a gradually progressive neoplasm cogitated within an elderly population, appearing as a pale, tan or reddish papule, indurated plaque or a nodule. The lesion is generally discerned upon scalp, forehead, face, neck, trunk, upper extremities, temporal or occipital region, nape or lower lip and demonstrates a varying magnitude betwixt 0.4 centimetre to 8 centimetres with a mean dimension of 2.8 centimetres. Majority (80%) of lesions demonstrate a clear, tumour-free margin. Prior to appropriate detection, the tumefaction can occur from 2 months to up to 50 years, followed by rapid tumour progression [3,4]. As trichilemmal carcinoma can be frequently misinterpreted as a benign lesion, a clinical demarcation is necessitated from neoplasms such a squamous cell carcinoma, basal cell carcinoma, nodular variant of malignant melanoma or a kerato-acanthoma .
Trichilemmal carcinoma is an exceptional, malignant neoplasm delineating histological features of an intermediate to high grade malignancy. Grossly, the lesions are polypoid, exophytic, ulcerated, nodular or haemorrhagic [4,5]. On microscopy, trichilemmal
carcinoma demonstrates diverse configurations such as solid,
lobular or a trabecular pattern of growth. Sharply defined,
infiltrative tumour lobules depict a pushing tumour perimeter
and a hyaline membranous envelop which can be highlighted
by a periodic acid Schiff’s (PAS) stain. Cellular constituents
configuring the lobules are enlarged tumour cells impacted with
clear or pale-staining, eosinophilic cytoplasm which is reactive
to periodic acid Schiff’s (PAS) stain with diastase sensitivity and
non-reactive to mucin stains. Peripheral palisading of cells, subnuclear
vacuolization and numerous mitotic figures are observed.
Foci of pilar subtype of keratinization and few dyskeratotic cells
are discerned. Zones of actinic damage demonstrate superficial
cutaneous ulceration. The tumour delineates a pagetoid form
of dissemination or infiltration into the deep-seated dermis
can be enunciated [4,5]. Immune reactivity to cytokeratin along
with immune non-reactive carcinoembryonic antigen (CEA) and
epithelial membrane antigen (EMA) are exemplified .
Trichilemmal carcinoma requires a segregation from various
clear cell carcinomas arising from the cutaneous surfaces.
Trichilemmoma and clear cell hidradenoma are benign tumours
which lack an infiltrative pattern of tumour growth and cytological
atypical . Trichilemmal carcinoma and malignant proliferating
trichilemmal tumour are described as two distinct entities wherein
malignant proliferating trichilemmal tumour is engendered from
a pre-existing trichilemmal cyst and is accompanied by a distinct
metastatic potential .
Trichilemmal carcinoma is amenable to a comprehensive
surgical extermination with a broad perimeter of uninvolved,
circumscribing soft tissue. As the appropriate therapeutic
management is a complete surgical eradication of the neoplasm
with a clear, tumour free surgical margin, a subsequent, periodic
surveillance is advantageous, especially in the absence of
cogent adjuvant therapy . Histologically tumour free surgical
perimeter is critical for assessing features such as localized
tumour infiltration or a potential, localized tumour reoccurrence.
Localized tissue reconstruction with rotation flap and skin
grafting can be adopted following adequate surgical eradication
of the neoplasm. Regardless of a comprehensive surgical excision
with a tumour free margin, tumour reoccurrence can appear
within an estimated 8% instances [7,8]. Adequate surgical
extermination of the neoplasm with satisfactory eradication
of the surgical border is a safe, cost-effective and an efficacious
methodology of treating trichilemmal carcinoma. Post- operative
follows up is mandated to facilitate a preliminary discernment
of disease reoccurrence and distant metastasis [7,8]. Optimal
treatment of trichilemmal carcinoma with metastasis lacks
consensus and an established chemotherapeutic or adjunctive
treatment regimens are absent. Regional lymph node and distant
metastasis are accompanied by a mortality rate of roughly (8%)
following a surgical extermination and cogent chemotherapy
with cisplatin and vindesine is recommended. Combination
therapy with cisplatin and cyclophosphamide can induce with a
partial remission as it controls the tumour progression although
alleviation of the tumefaction is absent . Concurrence of 5-
fluouracil with cisplatin is accompanied by an inferior prognosis.
Moreover, administration of cisplatin with adriamycin and
vindesine (CAV treatment) recapitulates the therapeutic regimen
of high grade, advanced squamous cell carcinoma. Reoccurring
lesions of trichilemmal carcinoma associated with distant
metastasis are generally refractory to therapy. Administration of
cogent chemotherapy can curb tumour progression. Following
adequate surgical of the neoplasm, tumour reoccurrence is usually
absent for a period of few months. Definitive, discernible distant
metastasis is optimally treated with systemic chemotherapy
comprised of a combination of cisplatin and vindesine or cisplatin
with cyclophosphamide [7,8] (Figures 1-9).