Congenital epidermoid cyst associated with mucus retention cyst in Wharton's duct of a newborn. Report of an unusual case

Abstract

<h3>Objectives</h3> The differential diagnosis of cystic swellings involving the floor of the mouth includes various lesions, such as dermoid, epidermoid or lymphoepithelial cysts and ranulas. However, coexistence of such conditions, pos- sibly with a cause-and-effect relationship, is rare. Herein, we present a case of congenital epidermoid cyst in asso- ciation with mucus retention cyst in the floor of mouth of a newborn. <h3>Findings</h3> A 6 months old female infant was referred for evaluation of a "pearly" yellowish swelling in the floor of mouth, first noticed by her pediatrician just after birth. Slow enlargement of the lesion was reported. Clini- cal examination revealed a yellowish nodule with overlying prominent vasculature in close association with the orifice of the left submandibular duct, posteriorly transitioning to a diffuse bluish cystic swelling of the left floor of mouth. With a provisional diagnosis of a developmental cyst and/or ranula, a surgical excision was performed under general anesthesia. Intraoperatively, an anterior round lesion was identified, extending posteriorly towards the submandibular gland as an elongated cylindrical cystic dilatation. Histopathologic examination revealed a well- defined cystic cavity in the anterior aspect lined by keratinized stratified squamous epithelium with compact keratin deposition inside the lumen. The cystic lesion showed continuity with a dilated salivary duct aligned by cylindrical, cuboidal or pseudostratified epithelium. A final diagnosis of epidermoid cyst intimately associated with a mucus retention cyst (ranula) of the submandibular duct was rendered. <h3>Conclusions</h3> The coexistence of two cystic lesions in the floor of the mouth with features of epidermoid and mucus retention cyst, respectively, is rare and its pathogenesis intriguing, especially in a newborn. Theoretically, the two lesions may be coincidental, although a more reasonable explanation is that a congenital epidermoid cyst, inciden- tally developing adjacent to the submandibular duct orifice, caused obstruction and secondary mucus retention phenomenon.