Dermoid cysts are developmental malformations due to a defect in the fusion of embryonic lateral mesenchymatic layers during the fifth week of embryological development. Thirty-four percent of dermoid cysts occur in the head and neck area, of which 6.5% are in the floor of mouth. We present a rare case of a 17-year-old female with epidermoid cyst presenting in the floor of the mouth. A working diagnosis of a "plunging ranula" was concluded following salivary gland multidisciplinary team (MDT)

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... eting and the patient subsequently underwent an excision of lesion with right sublingual gland via an intraoral approach under GA. However, the pathology revealed the lesion consistent with an epidermoid cyst. We discuss the numerous pathological conditions that can affect the floor of the mouth, and differential diagnoses of lesions of a development, inflammatory, obstructive or neoplastic origin. Imaging aids such as ultrasound, MRI, and CT of head with contrast area are of valuable importance for estimating tumor margins and lesion composition, and assessing infiltration in surrounding tissues along with MDT which give platform with other departments to help form a working diagnosis and guide surgical approach.