This is a 44 years old, with a history of diabetes on insulin and dermatomyositis for which she has been followed at the hospital for 4 years, currently on oral corticosteroid following a relapse of her disease. She reported the appearance of 3 nodules in the vulvar area, 2 of them were painful, evolving for 6 years and gradually increasing for 4 years.

The clinical examination found 3 brown nodules in the genital area, with firm consistency, well limited, fixed measuring 1 cm each (Figs. 1a and 1b). The rest of the examination was unremarkable and showed no adenopathy. The dermoscopy was non-specific. An excisional biopsy of the 3 nodules has been performed. The histology was in favor of nodular hidradenoma (Fig. 2). After 2 years of follow-up, no recurrence was observed.

	Figure 1: (a and b) Vulvar nodule.
	Figure 2: Histopathology showing a nodular proliferation located in the dermis with a polygonal cells and clear cytoplasm.

Nodular hidradenoma is a rare benign adnexal tumor, usually of apocrine or eccrine origin. Its histogenesis is not well known, therefore nodular hidradenoma is also known as eccrine hidradenoma, clear cell hidradenoma, eccrine acrospiroma, and eccrine sweat gland adenoma [1].

It affects all ages, mainly women between 40-80 years old. Cases of recurrence, malignant transformation and metastases have all been described. It is usually located in the head, the neck, the anterior part of the trunk and the extremities. The vulvar localization has never been described before. The histological features of hidradenoma shows a cystic cavity lined with an epithelium with a hyalinized stroma and polygonal cells with clear cytoplasm. Dermoscopy wasn’t specific in our patient but features usually found are pinkish or bluish homogeneous areas with vascular and white structures [2].

The main differential diagnosis of genital location is papilliferous hidradenoma [3].

Although it is benign, excision and monitoring are necessary because of the risk of transformation and recurrence.

REFERENCES

1.El Amine El Hadj O, Mhiri M, Goucha A, Ben Hassouna J, Adouni O, et al. Eccrine hidradenoma of the breast:distinct pathological lesion mimicking a carcinoma. Our Dermatol Online. 2016;7:400-2.

2.Patricia S, Aimilios L, Luis Javier DP, Isil K, Carolina M, et al. Dermoscopy of nodular hidradenoma, a great masquerader:a morphologicalstudy of 28 cases. Dermatology. 2016;232:78-82.

3.Khalidi M, El Amraoui M, Hjira N, Boui M. Papilliferous hidradenoma:A rare vulvar tumor. Our Dermatol Online. 2021;12:51.