Clarion and Crystal-Clear Cell Acanthoma Reviewed

Clear cell acanthoma was portrayed primarily by Degos [1]. Clear cell acanthoma is also referred to as Degos’ acanthoma or pale cell acanthoma and is cogitated as an asymptomatic, benign epidermal tumor devoid of gender predilection. Clear cell acanthoma defines a distinct entity on clinical and histological evaluation. Of obscure etiology, the disorder is possibly engendered by inflammation. Apart from exemplifying a benign epidermal tumor, it can be contemplated as a reactive inflammatory dermatosis. Definitive diagnosis of clear cell acanthoma can be challenging as the lesions simulate several benign and malignant skin conditions. Traumatic or drug induced genesis of the neoplasm lacks approval and the disease is of an essentially unknown pathogenesis [1,2].


Histological Elucidation
Characteristic histological attributes of clear cell acanthoma includes abundant representative clear cells or cells with transparent cytoplasm, typically confined to the epidermis. Clear cells abound in glycogen and are reactive to periodic acid Schiff's (PAS) stain, labile with diastase. Occasionally, clear cells are absent, and cells can be non-reactive to periodic acid Schiff (PAS) stain. Lateral margin of the lesions is sharply defined and well demarcated. On microscopy, lesions are constituted of uniform, pale keratinocytes or pale epithelial cells and demonstrate distinct foci of transformation from adjacent normal, uninvolved superficial epidermis. Keratinocytes enunciate abundant quantities of pale staining cytoplasm and centric nuclei [5,6]. Keratinocytes appear as palely stained cells on account of excessive amounts of incorporated glycogen and are delineated distinctly with periodic acid Schiff's (PAS) stain which can be eliminated with diastase that assimilates the glycogen.
Clear cells are especially enunciated within the epidermis except the basal layer. Granular epidermal cell layer is absent, and the lesions are devoid of melanin. Supra-papillary epidermal plate is attenuated except the within the region of adnexal epithelium. Clear cell acanthoma is composed of squamous epithelium where the superficial epidermis demonstrates acanthosis with psoriasiform epithelial hyperplasia accompanied by amalgamation of adjacent rete ridges. Dermis, predominantly papillary dermis, displays a diffuse inflammatory infiltrate composed of neutrophils accompanied by distended, enlarged vasculature. Additionally, aggregates of intra-lesioned neutrophils are classically exemplified within the superimposed parakeratotic epithelial crust [6,7]. Lesions of clear cell acanthoma manifesting aforesaid epithelial modifications are sharply defined and segregated from abutting, uninvolved squamous epithelium Histological description of clinical variants of clear cell acanthoma necessitate the demonstration of classic, pale staining, minimally enlarged epithelial cells confined to the epidermis, the elucidation of which is mandatory for definitive diagnosis of clear cell acanthoma.

Differential Diagnosis
Segregation of clinical lesions of clear cell acanthoma is mandated from dermatofibroma, pyogenic granuloma, irritated seborrheic keratosis, keratoacanthoma, actinic keratosis, plaque psoriasis, eccrine poroma, viral warts or malignant cutaneous tumors such as basal cell carcinoma, squamous cell carcinoma, malignant melanoma and metastatic cancer. On extraneous examination, lesions simulate those of psoriasis, lichen planus and discoid lupus erythematosus [7,8]. Demarcation is required from psoriasis vulgaris. Lesions depict a distinct transformation betwixt the normal, uninvolved epidermis and epidermal accumulations of clear, pale cells, although clear cell aggregates can be absent. Distinction from trichilemmoma is necessitated. Lesions are devoid of neutrophils. Cellular aggregates are circumscribed by dense, eosinophilic basement membrane material and display a peripheral palisade. Several squamous eddies can be cogitated.

Investigative Profile
Pertinent dermatoscopy can augment diagnostic precision. Dermatoscopic pattern of clear cell acanthoma was appropriately elucidated by Blum in 2001. Clear cell acanthoma exemplifies singularly unique attributes on dermatoscopy which depicts a variegated reddish or purple lesion demonstrating a serpiginous pattern akin to a "string of pearls". Characteristic red dots, globules and coiled (glomerular-like) vasculature is configured in a serpiginous manner. Augmentation of serpiginous articulations are prominently symmetric. Occasionally the vascular arrangement in incomplete or partially evolved with the emergence of "forme fruste" or a compression artefact. Discoloration due to melanin (black, brown, gray, blue) is not evident in the lesions. Lesions are described as symmetrical, partially homogeneous or cogitating a bunch-like configuration with pinpoint capillaries. Lesions of clear cell acanthoma are, nevertheless, distinct [8,9]. Dot or coiled (glomerular-like) blood vessels are characteristic of reactive inflammatory dermatosis such as psoriasis, pityriasis lichenoid and discoid eczema. However, red dots and coiled vasculature are uniformly disseminated and do not amalgamate to configure a serpiginous, vascular arrangement. Infrequent dermatoscopic Copyright © Anubha Bajaj TTEH.MS.ID.000520. 1(4).2019 features of clear cell acanthoma include areas of hemorrhage, orange-tinted superficial keratinous incrustation and a collarette of translucent scales appearing on the periphery. Application of polarized dermatoscopy in evaluating clear cell acanthoma depicts the emergence of numerous crystalline structures [8,9].

Therapeutic Options
As clear cell acanthoma is a benign epidermal tumor and demonstrates a classic serpiginous vascular configuration, therapeutic surgical eradication is unnecessary in miniature, asymptomatic lesions. As it can be challenging to ascertain the nature of the lesion as benign or malignant, comprehensive surgical eradication is the recommended therapeutic option [9,10]. Cogent therapeutic strategies are pertinent to the magnitude, site and quantification of lesions as well as personal preference of the treating surgeon. Surgical extermination is optimal for solitary lesions. Additional therapeutic modalities include Moh's microsurgery, curettage, electro-fulguration, cryotherapy and carbon dioxide (CO 2 ) laser. Cryosurgery is beneficial in the management of multiple lesions. Benign clear cell adenoma is contemplated to be cured following a comprehensive surgical elimination which incorporates the sharply defined lateral contours. Exceptionally, reoccurrences can occur following adequate surgical excision (Figure 1-12); [11][12][13][14][15][16][17][18][19][20]. A tumor free surgical perimeter of 3 millimeters can be adopted as a pertinent therapeutic preference. Follow up can demonstrate an absence of reoccurrence of the lesion. However, close monitoring is necessitated on account of potential malignant conversion.