Epidermal inclusion cyst of the tongue - a rare entity

Clinical History

A 40-year-old female patient came to our department complaining of a swelling involving the left lateral border of the tongue. There was no history of fever before the onset of the swelling. On palpation, a firm to hard swelling with no associated pain was detected. The patient had difficulty in chewing food sometimes.

Imaging Findings

1. The high-resolution ultrasound shows a well-defined heterogeneous predominantly hyperechoic lesion measuring approximately 2.29x1.59 cm, involving the left lateral border of the tongue.

2. The MRI shows a well-defined lesion (1.5x1.0x1.2 cm) with mild peripheral enhancement, displaying signal intensity alteration seen in the anterior 2/3rds of the tongue on the left side (T1W image), however, T2w images show a hyperintense mass.

Discussion

Epidermal inclusion cyst, also known as dermoid cyst, is a congenital lesions caused by defective fusion of the embryonic lateral mesenchymal tissues. The tissue can originate from ectoblastic, mesoblastic or endoblastic tissues. A true epidermal inclusion cyst cavity is covered with keratinized epithelium with dermal appendices [1]. The epidermal inclusion cyst rarely occurs in the head and neck, with an incidence ranging from 1.6 to 6.9%. It constitutes less than 0.01% of all oral cysts [2, 3, 4]. Roser was the first to designate dermoid cysts in the floor of the mouth as epidermoid tumours [5]. The following theories of aetiopathogenesis of epidermal inclusion cyst have been proposed [6]:

i) Congenital inclusion of dermal and epidermal elements of germ layers in deeper tissues along the embryonic lines of fusion.
ii) Acquired traumatic implantation of dermal and epidermal elements of surface epithelium, which may proliferate and keratinize.
iii) Growth from a rest of totipotent cells displaced from the blastomere.

These cysts show variation in size and weight. The symptoms of dysphagia, dyspnoea and dysphonia may occur due to upward displacement of the tongue by these sublingual swellings. Furthermore, downward growth of an epidermal inclusion cyst may give rise to the appearance of a characteristic "double chin". These well-encapsulated lesions typically feel "dough-like" on palpation and their consistency may range from a cheesy, sebaceous to a liquefied substance [5, 7].
Fine needle aspiration cytology, ultrasound, CT and MR imaging provide essential information on the cyst location. Ultrasound findings comprise solid and cystic structures within a heterogeneous mass. On CT imaging, epidermal inclusion cysts appear as moderately thin-walled, unilocular masses filled with a homogeneous, hypoattenuating fluid substance with numerous hypoattenuating fat nodules, showing the pathognomonic "sack-of-marbles" appearance. On MR imaging epidermal inclusion cysts have a variable signal intensity on T1-weighted images and are usually hyperintense on T2-weighted images. Fine needle aspiration cytology has been advocated as an essential investigation. Treatment comprises total surgical excision. Recurrences are unusual after absolute surgical excision. Reports of malignant transformation of sublingual epidermoid to squamous carcinoma and basal cell carcinoma can also be found in the literature [4, 5, 8].

Differential Diagnosis List

Final Diagnosis

Epidermal inclusion cyst

URL:	https://www.eurorad.org/case/12785
DOI:	10.1594/EURORAD/CASE.12785
ISSN:	1563-4086