A rare differential diagnosis of a common clinical presentation

Abstract

A 23-year-old female presented with a several-month history of a persistent, painless swelling in the left groin. There were no associated symptoms and she had no significant past medical history. On examination, an irreducible, non-tender, 7 ¥ 5 cm swelling was palpable, and was unchanged with patient position. Ultrasound examination revealed a complex cyst. The patient was diagnosed with a left-sided hydrocele of the canal of Nuck. Elective surgical exploration of the left groin revealed a cyst within the inguinal canal, which was excised. The internal inguinal ring was then closed. Pathologically, the cyst was thin-walled and contained yellow, cheesy material. It was lined by keratinizing stratified squamous epithelium with hair shafts and sebaceous glands. Notably, no mesothelial cells were seen. These features are suggestive of a dermoid cyst rather than a hydrocele of the canal of Nuck. Dermoid cysts are congenital cutaneous inclusion cysts that occur at lines of embryonic epithelial closure, commonly found in the face, neck and scalp. Histologically, they are lined with squamous epithelial cells containing hair follicles or sebaceous glands. The cysts can contain sebaceous material, keratin and hair. Dermoid cysts of the round ligament are rare and have been described in only a few case reports. Available literature suggests that these lesions will persist until surgical excision, and there are no reports of malignant transformation. Dermoid cysts of the round ligament and hydroceles of the canal of Nuck are examples of rare pathologies causing a lump in the groin. Ultrasound examination may be informative, although preoperative diagnosis remains challenging. Surgical excision and histological examination is the accepted management of both conditions. Rare pathologies should be considered when a patient presents with a non-tender, irreducible mass in the groin. Awareness of uncommon pathologies can prevent intra-operative surprises and may alter the counselling of a patient undergoing surgical exploration. References