Carcinoma showing thymus-like differentiation (CASTLE): a case report.

INTRODUTION: Carcinoma showing thymus-like differentiation (CASTLE) is a rare malignant thyroid cancer. We report a case of CASTLE treated with surgery and adjuvant external neck radiation therapy.

MATERIALS AND

METHODS

We experienced a case of CASTLE in a 63-year-old man, who presented with a neck mass due to enlarged and hard thyroid gland, most notably in the right lobe, without palpable cervical nodes.

RESULTS

Total thyroidectomy was performed for both diagnostic and therapeutic purposes. Histologic examination of the specimen showed a "thymus like" thyroid cancer; the tumor, partially circumscribed, lobulated, involved both lobes, and in more points reached the capsule of the organ and infiltrated perithyroid muscle tissue. After immunohistochemical assay (CK19 +, CK20 -, thyroglobulin -, calcitonin -, CD5 +, CD117 +), a diagnosis of CASTLE was made.

DISCUSSION: CASTLE is a rare, malignant tumour of the thyroid gland, with histopathological features similar to squamous cell carcinoma, but with a more favourable prognosis. Preoperative diagnosis is difficult. CASTLE is usually cured surgically with total thyroidectomy and selective neck dissection, followed by radiotherapy.

CONCLUSIONS

Surgery and radiotherapy are effective to manage thyroid CASTLE tumors.