Abstract

Primary squamous cell carcinoma is a rare malignant tumor of the thyroid gland. It was firstly descibed by von Karst in 1858. Although the histogenetic origin of squamous cell carcinoma of the thyroid has been debated, squamous metaplasia of the follicular cells is most widely accepted histogenetic theory for this neoplasm. The authors experienced two cases of primary squamous cell carcinoma of the thyroid gland. The first case was a 64 years old male patient who had been suffered due to suddenly developed palpable mass on the anterior neck, two months prior to entry. On operation, there was an ill defined nodular mass, 3cm in diameer, on the left lower thyroid. It had homogeneous light yellow cut surface with firm consistency. Microscopically, the thyroid follicles were replaced by dense fibrous tissue containing nests of neoplastic squamous cell. There was marked chronic inflammatory cell infiltration in the fibrous tissue. The second case was a 52 years old male patient who had been suffered because of painful palpable mass on the anterior neck for 20 days. He had been showed hoarseness since eight month prior to entry. Laryngoscopic examination revealed paralysis of the right vocal cord, but other pathological findings were not found. On operation, the thyroid gland was fixed to the trachea. Both lobes of the thyroid showed homogeneous tan brown cut surface with focal honey-comb appearance and diffuse light yellow miliary infiltration. Microscopically, there were numerous nests of neoplastic squamous cells with keratin pearls. Benign metaplastic squamous cells were observed around the carcinoma lesion. transitional zone between the metaplastic squamous cells and follicular epithelial cells were observed. Some follicles were entrapped within the neoplastic tissue.