A 54-year-old male patient was admitted to our clinic, complaining about having back pains for approximately three months. The patient had no history of hypertension, diabetes mellitus, tuberculosis or any neck swelling, and neurological examination showed no abnormalities. A lumbosacral spine MRI (magnetic resonance image) scan revealed multiple lesions in the L4, L5, S1 vertebra bodies, sacral bone and left pelvis bone, suggesting of a metastatic disease (Fig. 1). A PET (positron emission tomography) scan showed abnormal hypermetabolic foci in the L4, L5, S1 vertebra bodies, sacral bone, left pelvis bone and left thyroid lobe, giving further indication of metastatic tissues (Fig. 2).
The patient had no previous history of neck irradiation and his family history was negative for any form of thyroid disease. Clinical examination of the neck using ultrasound revealed a left-sided nodule of 2 cm in size. Routine blood tests and thyroid function tests were also within normal limits. However, FNA (fine needle aspiration) of thyroid tumor and biopsy of the vertebra bone confirmed the presence of a metastatic carcinoma.
Once the carcinoma was confirmed, a total thyroidectomy and level VI neck dissection was conducted. Histology analysis revealed a microscopic focus of intrathyroidal low-grade MEC within the 2 cm nodule, as well as in one lymph node, however, no papillary features were identified. Postoperative, the patient was treated with palliative external beam radiotherapy (30 Gy) to the vertebra bodies, sacral bone and left pelvis bone to relieve pain. The patient did not receive radioactive iodine therapy. Six months after treatment, the patient died due to severe pain and fatigue caused by the disease.
In pathological studies that followed, there were no indicators of papillary carcinoma or follicular carcinoma, and no evidence of Hashimoto's thyroiditis in the thyroid parenchyma. Immunohistochemical analysis showed positive results for thyroglobulin, confirming that the carcinoma primary origin site is the thyroid, and thus the diagnosis of thyroid mucoepidermoid carcinoma was confirmed (Fig. 3).