Nodular hidradenoma is a non-melanocytic adnexal tumor arising from the epithelial cells of the excretory duct of the sweat glands, usually benign in nature, with only a few cases of malignant transformation reported [1].

It is most common in middle-aged and elderly subjects, with a slight female predominance.

It presents as painless solitary, solid, or cystic lesions, nodules, plaques, or papules, from 0.5 cm to 10 cm in size, often less than 2 cm. A few cases of giant forms have been reported, the largest measuring 9.5 cm [2].

They are most commonly found on the trunk, the head, and the extremities.

The most common dermoscopic features of the pigmented forms are a bluish homogeneous area that corresponds histologically to an increase in melanin pigment seen in some cases, the presence of hemorrhages in some cystic spaces, and/or Tyndall’s phenomenon, given the cystic nature and dermal localization of the tumor, whitish areas that correspond to the fibrovascular or hyalinized stroma [3], and vascular structures such as telangiectasias, polymorphic vessels, and irregular linear vessels.

The diagnosis is histological due to the clinical and dermoscopic similarities with malignant tumors, especially basal cell carcinomas and melanomas.

The definitive treatment is surgical excision with safety margins given its high recurrence rate. We report a case of a giant nodular hidradenoma of the scalp.

A 19-year-old woman presented with a six years history of a scalp nodule having undergone 2 excisions with recurrence. The clinical examination showed a well-limited tumor of soft round consistency measuring 6 cm located at the occipital level (Fig. 1a). Dermoscopy showed bluish and whitish homogeneous areas without structures and irregular linear vessels (Fig. 1b). Doppler ultrasound showed a solid cystic lesion in the scalp of the medial occipital region. Surgical large excision was performed without recurrence.

Figure 1: (a) Clinical image showing a well-limited tumor of soft round consistency measuring 6 cm located at the occipital level. (b) Dermoscopy showed bluish and whitish homogeneous areas without structures and irregular linear vessels.

Consent

The examination of the patient was conducted according to the principles of the Declaration of Helsinki.

The authors certify that they have obtained all appropriate patient consent forms, in which the patients gave their consent for images and other clinical information to be included in the journal. The patients understand that their names and initials will not be published and due effort will be made to conceal their identity, but that anonymity cannot be guaranteed.

REFERENCES

1. Yoshida Y, Nakashima K, Yamamoto O. Dermoscopic features of clear cell hidradenoma. Dermatology. 2008;217:250–1.

2. Diab M, Gabali A, Kittaneh M. Malignant acrospiroma:A case report in the era of next generation sequencing. BMC Cancer. 2017;17:221.

3. Sgambato A, Zalaudek I, Ferrara G, Giorgio CM, Moscarella E, Nicolino R, Argenziano G. Adnexal tumors:clinical and dermoscopic mimickers of basal cell carcinoma. Arch Dermatol. 2008;144:426.