Intrathyroidal epithelial thymoma: An entity distinct from squamous cell carcinoma of the thyroid

Abstract

We report 3 cases of intrathyroidal epithelial thymoma, a clinicopathologic entity distinct from squamous cell carcinoma of the thyroid. Two patients are long-term survivors among 5 postoperative patients with squamous cell carcinoma of the thyroid. One has been free from the disease for 17 years, and the other with local recurrence died of an unrelated disease 18 years after the surgery. The diagnosis in these 2 was corrected to intrathyroidal epithelial thymoma following a review of the histological findings. These 2 tumors consisted of tumor cell nests resembling poorly differentiated squamous cell carcinoma surrounded by many lymphocytes. Features discriminating thymoma from squamous cell carcinoma included the lack of foci of anaplastic carcinoma and papillofollicular tumor, which are seen in squamous cell carcinoma of the thyroid. Two of the 3 patients with squamous cell carcinoma died within 1 year. We have found recently another case of thymoma.The present observations indicate that: thymoma can arise in the thyroid gland presumably from aberrant thymic tissue, mimicking squamous cell carcinoma; and the prognosis of thymoma is favorable. Therefore, it is important to discriminate thymoma from squamous cell carcinoma of the thyroid, which is usually fatal.We had the opportunity to observe 3 patients with intrathyroidal epithelial thymoma and 3 with squamous cell carcinoma of the thyroid. To our knowledge, there has been no previous reports of epithelial thymoma in the thyroid gland. Squamous cell carcinoma rarely occurs in the thyroid gland, and is

Clinical Analysis of Thyroid Carcinoma Showing Thymus-Like Differentiation: Report of 8 Cases

“…6,20 Some of the literature has reported that postoperative radiation could prevent locoregional recurrence. 1,5,9,21 In our study, 7 of 8 patients accepted postoperative radiation, and no locoregional recurrence occurred in 8 cases. For locoregional recurrence, Sun et al reported that recurrences may be controlled by salvage surgery with subsequent operation and/or radiotherapy.…”

“…It was originally described as intrathyroidal epithelial thymoma by Miyauchi et al in 1985. 1 In 2004, this disease was designated as an independent clinicopathologic entity among thyroid carcinomas according to the World Health Organization classification of tumors of endocrine organs. 2 Thyroid CASTLE may arise from an ectopic thymus or branchial pouch remnants in the thyroid gland, which retain the capability of thymic differentiation.…”

“…1,12,14,15 Immunohistochemical studies can differentiate thyroid CASTLE from other malignant thyroid neoplasms. Similar to thymic carcinoma, thyroid CASTLE is immunohistochemically positive for CD5, but negative for calcitonin, thyroglobulin, and TTF-1.…”

A Case of Malignant Thymoma Mimicking Thyroid Carcinoma: A Pitfall in Fine-needle Aspiration

“…Thyroglobulin is a protein specifically produced in the thyroid. So, when the tumor cells are stained positively for thyroglobulin, we can diagnose the tumor as thyroid in origin [8][9][10]. In our case, since no cells in the tumor were stained for thyroglobulin, we finally diagnosed it as thymoma.…”

Primary Squamous Cell Carcinoma of the Thyroid: Report of Three Cases

“…There are some theories concerning its origin. Some reports suggest that the squamous cells were derived from embryonic remnants such as the thyroglossal duct, thymic epithelium and ultimobranchial body remnants [1][2][3][4]23]. Another theory is that environmental stimulus like thyroiditis or inflammation may be associated with SCC [5,6].…”