Endocrine Abstracts

Thyroid carcinoma showing thymus-like differentiation (CASTLE) is an extremely rare thyroid neoplasm. This type of tumour may arise from branchial pouch remnants or ectopic thymus and is considered as independent clinicopathological entity of thyroid neoplasms. There have been only about 100 cases described in the literature, so far. Here, we have retrospectively analyzed the data from histopathology and clinics of a 70 year old female patient with thyroid CASTLE who underwent total thyroidectomy in 2009 due to thyroid nodule in the right lobe (25×25×30 mm) and suspicion of papillary thyroid carcinoma in the fine needle aspiration biopsy. At that time histopathological examination suggested presence of metastasis to the thyroid likely from the ovary or thymus however, the detailed clinical and imaging study did not confirm that these organs could be the source of this lesion. In February 2011 patient underwent neck lymphadenectomy that revealed metastases to the lymph nodes with unknown origin but thyroid carcinoma was ruled out. Patient was all time under control of endocrinologist and oncologist. In May 2014 patient was again hospitalized and next lymphadenectomy was done. At that moment histopathology of the lymph nodes indicated CASTLE (HMWCK+, p63+, CD5+, bcl2+, CEA+, synaptophysin+, Calc−, THY−, TTF1−). Therefore, the thyroid specimens were reevaluated again, and the presence of CASTLE in the gland was also confirmed. In subsequent follow-ups there were no signs and symptoms of the disease recurrence. Thyroid CASTLE might be easy overlooked because of its rarity and similarity to some thyroid cancers like squamous cell carcinoma or anaplastic carcinoma. Complete thyroid resection and lymphadenectomy are important to improve the long-term survival and the locoregional recurrence rate, although CASTLE course is usually clinically indolent. The short review of the already published data regarding CASTLE was done.