An unusual foreign body in the floor of the mouth presenting as a gradually growing mass.

Foreign bodies in the upper aerodigestive tract represent one of the most common ENT emergencies, but patients with foreign bodies in the floor of the mouth rarely present to the otolaryngologist. Only a very small number of these foreign bodies are embedded under normal mucosa and can result in lethal complications. In this article, we report the case of a 3-year-old girl with a gradually enlarging mass in the floor of the mouth. On physical examination at admission, there was a 2x3-cm, elastic, tender mass on the left side of the floor of the mouth, with the overlying mucosa intact and normal in color. Taking the palpable lymph nodes into consideration, a congenital lesion or a pediatric malignancy was suspected initially. A blue pen cap with a surrounding pneumatocele was found intraoperatively. After a careful reevaluation of a previous MRI, a check valve mechanism at the possible site of entry was detected, leading to a pneumatocele, thus explaining the constant growth of the mass. This is a unique case of a foreign body in the floor of the mouth, mimicking a congenital lesion or a pediatric malignancy. Thus, the possibility of a foreign body should not be underestimated when evaluating a child with swelling in the floor of the mouth.