An asymptomatic nodule in the vulva

Abstract

Conflict of interest: none declared. A 46‐year‐old Taiwanese woman presented with an asymptomatic, gradually enlarging nodule over the vulva for 2 years. She had attained menarche at the age of 16 years and her menstrual history was normal. At the age of 42 years, she underwent a total abdominal hysterectomy. Physical examination revealed a 20 × 20 mm, firm, mobile, nontender subcutaneous nodule over the left labium majus (Fig. 1). ... Surgical excision was performed under local anaesthesia. Histological examination revealed a well‐circumscribed subcutaneous nodule composed of elongated or branching tubules of various sizes in a fibrous stroma (Fig. 2a). These tubular structures consisted of single or double layers of epithelial cells with decapitation secretion of the apocrine type (Fig. 2b). Immunohistochemistry results for oestrogen and progesterone receptors were negative. ... What is your diagnosis? Fibroadenoma of the vulva. Fibroadenoma occurring in the vulva is uncommon. In our patient, the lesion is histologically identical to fibroadenoma of the breast. Whether vulvar fibroadenoma originates from the ectopic breast tissue or mammary‐like glands of the vulva is still under debate.1, 2 It has traditionally been believed to develop from the ectopic breast tissue of the vulva. In human embryogenesis, the mammary gland develops during the fifth week of gestation, when the mammary streak arises from the axilla to the groin, forming the so‐called ‘milk line.’ The milk line will disappear soon after its formation, except in the thoracic region, where it forms the mammary ridge. Incomplete regression of the mammary streak may result in the development of the ectopic breast tissue along the milk line. Ectopic breast tissue can have the same pathological processes found in the normal breast tissue, including fibroadenoma, fibrocystic disease, adenocarcinoma, phyllodes tumour and sarcoma.3 Some authors have suggested that positive staining for oestrogen and progesterone receptors could provide an additional evidence for the presence of the ectopic breast tissue. However, expression of these receptors is not specific for tumours of mammary origin.