A Caucasian, 60-year-old postmenopausal woman presented to our hospital for vulvar pruritus since 6 months. On physical examination, she presented with a 20mm pink solitary dermal nodule, with central ulceration, localized in the middle 1/3 of the right labium majus (Figure 1). She underwent excisional biopsy of the nodule. The microscopic examination revealed the diagnosis of hidradenoma papilliferum, with surgical free margins (Figure 2A and B). The patient received no adjuvant therapy.

Hidradenoma papilliferum of the vulva is a small and rare tumor that occurs in the anogenital region as a solitary, slow growing, firm and well delimited nodule or cyst-like lesion. It is more frequent in Caucasian women between 30 and 70 years old. It could present as an erythematous, blue or skin coloured nodule, sometimes with ulceration, mimicking a malignant process [1]. Although asymptomatic, it has occasionally been associated with itching, pain, bleeding or burning. Recent data suggest that hidradenoma papilliferum may derive from anogenital mammary-like glands - normal structures at the anogenital site and typically found in the sulcus between the labia minora and majora [1,2]. Due to the lack of distinctive clinical features, histological study is essential for diagnosis, since vulvar HP may mimic other benign or malignant lesions. The differential diagnosis includes vulvar ammelanotic melanoma, inflamed epidermal inclusion cyst, basal cell carcinoma, squamous cell carcinoma, extra-mammary Paget disease and Bartholin gland cysts/abcess [1,3]. Surgical removal is curative. No follow-up is recommended. Beyond the good prognosis, there are some reports about the simultaneous presence of malignant disease [3].

This case is an excellent addition to the literature, highlighting the variety in the clinical presentation. As the hidradenoma papilleferum is a benign lesion and malignant transformation is very rare, the standard recommendation is conservative excision rather than wide local excision.