Multiple Eruptive Clear Cell Acanthoma.

Sir,

A 54-year-old Chinese woman presented to our department with multiple itchy erythematous to brown rounded sessile nodules and irregular plaques on the perineum. No abnormal symptoms were described by the patient, except pruritus. The lesions started 7 years back and gradually increased in number and size. There were more than 20 lesions with the long axis of individual lesions varying between 5 to 50 mm. The sessile nodules were rounded, rufous or brownish red, and sharply circumscribed with irregular shape, sometimes with a peripheral collarette scaling or slightly moist surface [Figure 1]. Moreover, red pinpoint dots on a whitish background were observed under dermoscopy [Figure 2]. Clinical examination did not reveal any systemic abnormality. There was no history of trauma or insect bite. Differential diagnoses included seborrheic keratosis, amelanotic melanoma, squamous cell carcinoma, Bowen's disease, eccrine poroma, guttate psoriasis, and clear cell hidradenoma. An incisional skin biopsy from a plaque on her left inguinal region was performed.

Figure 1

Multiple erythematous to brown and irregular sessile nodules on the perineum

Figure 2

Dermoscopic appearance. Red pinpoint dots on a whitish background

Histologically, the specimen revealed a psoriasiform pattern with papillomatosis. Acanthosis, hyperkeratosis, parakeratosis, and neutrophils in the epidermis and inflammatory cell infiltration and blood vessel dilation in the upper dermis were seen [Figure 3a]. Clear cell was noted in the epidermis, and no nuclear division was recognized [Figure 3b]. As for the immunohistochemical study, those clear cells showed abundant cytoplasmic glycogen by periodic acid-Schiff staining [Figure 4a and 5a]. High molecular weight cytokeratins CK34βE12 [Figures 4c and 5b] and CK5/6 [Figure 4d] were intensely positive in almost all keratinocytes. Epithelial membrane antigen [Figure 4e] was also positive, while CK20 and carcinoembryonic antigen [Figure 4b, f and 5c] were negative in the keratinocytes. Taking together, a diagnosis of multiple clear cell acanthoma (CCA) was made.

Figure 3

Histopathological features showed acanthosis, hyperkeratosis, parakeratosis, and neutrophils in the epidermis and inflammatory cell infiltration and blood vessel dilation in the upper dermis. (a) Low magnification (H and E, ×40), (b) high magnification (H and E, ×200)

Figure 4

Pictograph showing (a) abundant cytoplasmic glycogen by periodic acid-Schiff, (b) complete negative for CK20 in the epidermis, (c and d) intensely positive of CK34βE12 and CK5/6, respectively, in almost all keratinocytes, (e) positive stain for epithelial membrane antigen, (f) negative stain for carcinoembryonic antigen in tumor cells (IHC, ×100)

Figure 5

Pictograph showing (a) abundant cytoplasmic glycogen by periodic acid–Schiff, (b and c) intensely positive of CK34βE12 and CK5/6, respectively, in almost all keratinocytes (IHC, ×200)

CCA is widely accepted as a benign epidermal neoplasm of unknown etiology. Degos et al. were first to describe CCA in 1962,[1] so this entity is also called Degos acanthoma or pale cell acanthoma.[2] Usually, CCA presents as solitary, brownish-red papule or nodule that always occurs in the lower extremity, with a diameter <20 mm.[3] It grows quite slowly and maintains the same shape and size for years. About 98% of CCA patients are beyond 40 year old and more often around 60 year.[4] Multiple CCA is a rare form of this disease. The case is presented here because of this rare form of multiple lesions on the perineum. Under dermoscopy, lesions presented red dots, due to glomeruloid vessels in a serpiginous pattern, which provided a significant clue in the diagnosis of CCA. However, it still depends on a skin biopsy and its unique histopathological features to make a certain diagnosis. As for the treatment, electrofulguration, cryotherapy, curettage, carbon dioxide laser, surgical excision, topical 5-fluorouracil, and topical calcipotriol were included.[5] The lesions of our patient are multiple; we chose microwave treatment for those giant lesions combined with the use of topical calcipotriol for those small papules.[5] Now, the patient is still in the follow-up.

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The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

This work was supported by the National Natural Science Foundation of China (81673045).

Conflicts of interest

There are no conflicts of interest.