Malignant Granular Cell Tumor of the Thyroid: A Case Report

Takehito Igarashi, Ritsuko Okamura, Tomo Jikuzono, Akira Shimizu, Shinichi Tsuchiya, Kazuo Shimizu


Granular cell tumor is usually a benign tumor derived from nerve cells, occurring most often in the head and neck. Granular cell tumor originating from the thyroid gland is extremely rare and to date, none has been reported to exhibit malignant characteristics. We report a case of thyroid granular cell tumor with tracheal invasion. The patient was a 53-year-old man presenting a nodule in the left lobe of thyroid gland identified incidentally during a health check. The nodule was hard and elastic, and had a size of 3.5 cm in diameter. Fine needle aspiration was performed and cytology revealed clusters of cells with acidophilic cytoplasm. Considering the differential diagnosis from Hurthle cell neoplasm, diagnostic lobectomy was performed. During operation, tracheal invasion was identified, suggesting invasive follicular carcinoma. We therefore performed a total thyroidectomy with removal of the involved tracheal wall. The tumor was diagnosed postoperatively as thyroid granular cell tumor with tracheal invasion. Neither local recurrence nor distant metastasis was identified one year after the surgery. In this paper, we report and discuss this case with particular focus on the diagnostic difficulty for malignant granular cell tumor of thyroid.


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