Papillary thyroid carcinoma (PTC) is the most differentiated malignant thyroid neoplasm. Local metastases of PTC commonly occur in the regional lymph nodes, while distant metastases are mainly to the lung and bone. The case of a patient with PTC who presented with swelling of the parotid gland and neck, mimicking a primary parotid neoplasm, is presented herein. This case is unique due to the unexpected initial presentation of PTC with no signs of disease in the thyroid gland.
Metastasis to the salivary glands accounts for 3.2–10% of all salivary gland tumours. In addition to direct invasion by tumours in the immediate vicinity, the parotid glands may also be the site of haematogenous and lymphatic metastasis. The majority of metastases to the parotid glands are from cutaneous tumours of the scalp, face, external ear, eyelids, or nose . Metastasis from primary sites below the head and neck region are uncommon and usually derive from carcinomas of the lung, breast, kidney, colon, and prostate .
Metastasis of papillary thyroid carcinoma (PTC) to the parotid gland is very uncommon and is not well documented. Mathew et al. identified only five previous reports in their case report .
The case of a patient with PTC who presented with swelling of the parotid gland and neck, mimicking a primary parotid neoplasm, is described herein. This case is unique due to the unexpected initial presentation of PTC with no signs of disease in the thyroid gland.
A 62-year-old man presented with swelling in the right neck region and around the ear of 1-year duration. The mass had been growing in size for the previous 2 months. Physical examination revealed a non-tender, solid mass in the right neck region. Computed tomography (CT) and magnetic resonance imaging (MRI) of the neck revealed a single solid mass with cystic–necrotic and calcified areas in the right neck and parotid region ( Fig. 1 A).
Fine-needle aspiration biopsy (FNAB) revealed adenocarcinoma. Parotid adenocarcinoma was considered at diagnosis. In order to excise the entire mass, which involved both the deep and superficial lobes of the parotid gland and invaded the internal jugular vein, a total parotidectomy with radical neck dissection was performed during the operation.
Histopathological examination revealed a sero-mucous gland structure and infiltration of tumoural cells into the lymphoid structures surrounding this gland ( Fig. 1 B). The tumoural structure comprised a papillary carcinoma with different histological variants at different sites ( Fig. 2 A). Large eosinophilic cytoplasm was observed at sites with the Hürthle variant ( Fig. 2 B). Immunohistochemistry revealed reactivity of tumoural cells for cytokeratin 19 (CK-19), HBME-1, galectin 3, thyroglobulin, and thyroid transcription factor 1 (TTF-1) ( Fig. 2 C). These findings confirmed a diagnosis of ‘metastasis of thyroid papillary carcinoma with Hürthle cell and follicular variant’. The lymph nodes were reported to be tumour-negative on histopathological analysis of the neck dissection material.