Videodermatoscopy improves the clinical diagnostic accuracy of multiple clear cell acanthoma

ARTICLE

Auteur(s) : Francesco LACARRUBBA, Rocco DE PASQUALE, Giuseppe MICALI

Dermatology Clinic, University of Catania, Piazza S. Agata La Vetere, 6, 95124 Catania, Italy

Article accepted on 8/09/2003

Clear cell acanthoma (CCA) is a solitary benign epidermal tumor first described by Degos in 1962 [1]. It appears clinically as a dome-shaped, sharply circumscribed, reddish papule, variable in size from 5 to 20 mm; a peripheral scaling collarette is characteristic, but not always present. CCA occurs frequently on the lower extremities of elderly patients, but other anatomic sites (trunk, upper extremities) have been reported. The etiology is not well understood; although some authors suggest that the lesion may represent a benign epithelial neoplasm, others consider the disease as a localized reactive inflammatory dermatosis (pseudotumor) [2, 3].

Multiple lesions (from 2 up to 400) are rarely encountered and less than 30 cases have been described [2]. The rate between solitary and multiple CCA is estimated to be 1:9-1:15 [4]. The mean age of onset is about 52 years, with equal frequency in men and women [5]. Ichthyosis and varicose veins are the most frequent associated findings.

The differential diagnosis of single and/or multiple CCA includes histiocytomas, seborrheic keratoses, basal cell carcinomas, pyogenic granulomas, syringomas, hidradenomas, leiomyomas, fibromas, perifolliculomas, disseminated granuloma annulare, lichen planus and sarcoidosis [6]. The diagnosis of CCA is usually confirmed by histologic examination.

We report a case of multiple CCA in which we performed videodermatoscopy in order to evaluate its usefulness as a non invasive diagnostic method.

Case report

A 69-year-old male presented with a 5-year history of asymptomatic papules on the legs, gradually increasing in number. Dermatological examination showed about 20 reddish, sharply circumscribed, smooth papules, with a diameter of 5-10 mm, sometimes with a peripheral scaling collarette, scattered on the legs (Fig. 1). Routine blood examination did not reveal any abnormality. Videodermatoscopic (Hirox Hi-Scope KH-2200) examination (magnification X30-X50) showed the same pattern in all lesions, consisting of symmetrical and homogeneous pinpoint-like vascular structures throughout the entire lesion (Fig. 2). These structures tended to be arranged in a net-like pattern (Fig. 2). At higher magnification (X200), each vascular structure appeared to have a bush-like aspect (Fig. 2). No other dermatoscopic features were observed. On the basis of anamnestic, clinical and dermatoscopic findings, a diagnosis of multiple CCA was suspected. Histologic examination of a papular lesion localized on the left leg confirmed the diagnosis, revealing acanthosis, papillomatosis and a sharply demarcated epidermal proliferation in which keratinocytes showed clear slightly larger cytoplasm with a positive PAS stain. In the superficial dermis capillaries were enlarged in the papillae.

Discussion

Videodermatoscopy [7] is a non-invasive technique widely used in the differential diagnosis of pigmented skin lesions utilizing epiluminescence microscopy techniques, that consist of application of a liquid (oil, alcohol or water) on the skin to eliminate light reflection. The same techniques allow visualization of the vascular pattern of either pigmented or unpigmented skin lesions, representing an important additional tool in the differential diagnosis. Dermal nevi, basal cell carcinomas, seborrheic keratoses, melanomas and melanoma metastases are some skin disorders in which videodermoscopic evaluation of vascular pattern may provide important diagnostic information [8-10]. Recently, a characteristic dermatoscopic vascular pattern of CCA has been described, consisting of “partly homogeneous, symmetrically or bunch-like arranged, pinpoint-like capillaries” [11]. In our patient, the presence of multiple CCA allowed us to examine with videodermatoscopy several lesions in various developmental stages. All examined CCA showed the same pattern: symmetrical and homogeneous pinpoint-like vascular structures throughout the entire lesion with no other dermatoscopic features; these structures tended to be arranged in a net-like pattern. At higher magnification (X200), each vascular structure appeared to have a bush-like aspect. Interestingly, this videodermatoscopic pattern corresponds to the histologic aspect of regularly elongated rete ridges and enlarged capillaries in the dermal papillae. For this reason, the dermatoscopic pattern of CCA resembles that of psoriasis and, possibly, of some other psoriasiform diseases (such as pityriasis rubra pilaris and certain forms of contact dermatitis) characterized by proliferation of the epidermis accompanied with dilated capillaries in the papillary dermis, thus implying the need for additional diagnostic criteria. Differential diagnosis from psoriasis is particularly relevant in the case of multiple CCA. Other cutaneous conditions, such as warts, actinic and seborrhœic keratoses, Bowen's disease, squamous cell carcinoma, hypopigmented Spitz nevus, melanoma and melanoma metastasis may sometimes show pinpoint-like vessels [8, 12]. In these instances, however, a correct evaluation of anamnestic and clinical features, along with additional dermatoscopic features, will help to address the correct diagnosis.
In conclusion, our study suggests that, although the dermatoscopic pattern of CCA is not specific, videodermatoscopy may improve the clinical diagnosis of single or multiple CCA, ruling out clinically similar disorders that do not show the same videodermatoscopic features of CCA. Examination of additional cases will allow confirmation that the described dermatoscopic vascular pattern is a constant finding of both single and multiple CCA. n

References

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