Endocrine Abstracts

Introduction: Carcinoma showing thymus-like differentiation (CASTLE) is a rare, low-grade thyroid carcinoma, with indolent clinical course and usually a favorable prognosis. The clinical and imagistic features are not specific for CASTLE but similar to other malignant lesions of the thyroid, making diagnosis difficult and reliant on immunohistochemical examination. The conclusive diagnosis requires pathological examination and positive cluster of differentiation 5 (CD5) immunoreactivity

Case Report: Hence, the present paper aims to present a rare case of CASTLE compressing the trachea in a 50 year-old female patient, after being misdiagnosed in another center with undifferentiated thyroid carcinoma, for which she underwent an unsuccessful surgical procedure followed by postoperative radiotherapy and chemotherapy. The patient sought out a second opinion, for the investigation of an 18 months history of persistent dyspnea, dry cough, weight loss, loss of appetite, and fatigue, associated with dysphagia and dysphonia. The patient underwent a challenging radical surgery, total thyroidectomy and cervical lymphadenectomy being performed. Histopathological analysis of the specimen showed large areas of fibrosis, large, round vesicular nuclei with small nucleoli, low cytoplasm and peritumoral lymphoplasmacytic infiltration. Immunostaining for CD5 was positive. Postoperatively, no adjunctive radiotherapy was recommended, no acute complications were reported, replacement therapy with Levothyroxine was initiated, metastatic follow-up was negative and there was no evidence of loco-regional recurrence after 6 months of follow-up.

Conclusion: The diagnosis of CASTLE is difficult and requires a rigorous histological analysis and positive CD5 immunoreactivity. The improvement of long-term survival is based on the level of tumoral invasion in the adjacent structures, absence of metastasis and successful resection of the tumor and neck dissection. The particularity of this case consists in emphasizing the importance of establishing the accurate diagnosis for obtaining optimized management, with the purpose of reducing unnecesessary procedures.