Linear Skin-coloured Papules on Scrotum: A Quiz

Joonsoo Park, Inyong Kim, Hyo Chan Jang, In Soo Chae, Kyungduck Park, Youngil Kim and Hyun Chung

Department of Dermatology, College of Medicine, The Catholic University of Daegu, 718-720 Daegu, Korea. E-mail: magincia@cu.ac.kr

A 4-year-old boy presented with skin-coloured papules for unknown period of time. The papules were asymptomatic but tended to spread over time. He had no past medical history, and there was no personal or family history of any skin disease. Physical examination revealed multiple linear arranged skin-coloured papules on the scrotum (Fig. 1A). A punch biopsy specimen was obtained from the lesion for haematoxylin-eosin (Fig. 1B).

Fig. 1. Physical examination revealed linear arranged skin-coloured papules on the scrotum (A). The cystic lesions in the dermis lined by epithelial cells with some decapitation secretion (B) (H&E × 400).

What is your diagnosis? 1. Linear epidermal naevus; 2. Median raphe cyst; 3. Lichen striatus; 4. Apocrine hidrocystoma; 5. Milia. See next page for answer.

Linear Skin-coloured Papules on Scrotum: A Comment

Diagonsis: Apocrine hidrocystoma

Haematoxylin-eosin staining of the specimen showed a couple of cystic lesions in the dermis lined by epithelial cells with some papillary projection (see Fig. 1B). The cyst wall was lined by columnar cells showing decapitation secretion. Superficial perivascular infiltration of inflammatory cells was also observed. The granules of the secretory cells were positive for PAS staining (Fig. 2).

 

Fig. 2. The granules of the secretory cells were positive for D-PAS (×200).

Apocrine hidrocystoma is a benign tumour arising from apocrine sweat gland. It presents as a solitary translucent nodule, usually on face, head, and neck. It rarely appears on the ears, scalp, chest, shoulders, or genitalia (1). Multiple lesions are also reported (2). It was first described by Mehregan (3) as a cystic proliferation of apocrine glands. Since then, a lot of cases have been reported worldwide, but rarely on the genitalia. The size of the tumour varies between 3 and 15 mm (4). Its colour can vary from skin-coloured to blue, or even red-brown and about 50% of cases are pigmented (5). These colour variations seem to be due to the Tyndall effect of the lipofucin-rich fluid content of the cyst, melanocytes, or contained iron (5). The differential diagnosis of apocrine hidrocystoma includes eccrine hidrocystoma, blue naevus, poroma, and epidermal cyst. Especially if the cyst occurs on genitalia, the median raphe cyst should always be ruled out. Moreover, as it is in this case, the linear distributed papular lesions could arrange in linear form and must be distinguished from linear epidermal naevus or lichen striatus. The histopathologic findings, such as decapitation secretion, PAS-positive and D-PAS-negative granules, can be helpful to distinguish the disease.

Simple excision can be both diagnostic and therapeutic option when the apocrine hidrocystoma presents as a solitary cystic lesion. Carbon dioxide laser vaporisation shows good result when treating multiple apocrine hidrocystomas (6).

References