Unusual Oral Cavity Metastasis From Follicular Carcinoma Of The Thyroid – A Case Report

摘要

Metastatic tumours in the oral cavity are relatively uncommon and account for 1% of all oral malignancies. The breast, the lung and the kidney are the common primary origin of metastasis. Metastasis to the oral cavity from a thyroid malignancy is very rare and cases described in literature are very few. We report a case of 70 year old lady who presented with a soft tissue swelling in the oral cavity without any other significant clinical findings. Ultrasound of the neck showed a very small anechoic area in the left lobe of thyroid. Fine needle aspiration cytology from both lesions showed malignant cells with follicular pattern. Introduction Metastatic tumours of the oral cavity are rare constituting approximately one percent of all oral malignancies1. Breast, lung and kidney are the primary origin of metastasis in 50% to 60% of the cases2. Thyroid malignancy metastasizing to the oral cavity is not very frequent and cases described in the literature are very few. We report one such rare case of oral cavity metastasis from a thyroid malignancy. Case Report A 70 year old lady presented with complaints of gradually increasing painful swelling in the oral cavity for three months. On examination of the oral cavity, a 7 x 6 cm well defined swelling with soft consistency was noted in the floor of mouth extending into the lower alveolus (Fig.1 and Fig. 2). The swelling bleeds on touch. There was no thickening or irregularity of mandible detected on clinical examination. There were no palpable cervical lymph nodes. No abnormality detected on other systemic examination.Based on the clinical findings, a provisional diagnosis of a primary oral malignancy was considered. Due to increase vascularity of the swelling, fine needle aspiration cytology (FNAC) was considered instead of biopsy and reported to have thyroid follicles. Ultrasound of the neck showed a 1.5x1x1 cm lobulated mass with central anechoic area in the left lobe of thyroid. There were no cervical lymph nodes detected. The FNAC of the thyroid swelling reveled follicular pattern. Based on the above investigations the provisional diagnosis of follicular carcinoma thyroid with oral cavity metastasis was made. A biopsy was further considered to confirm the diagnosis. The histopathological examination showed thyroid follicles which is positive for PAS stain. There was thickened capsule with capsular invasion (Fig.3 and Fig 4). The CT scan of head and neck revealed metastatic lesion arising from mandible extending into oral cavity (Fig.5).