Carcinoma showing thymic-like elements--a rare malignancy of the thyroid gland

Carcinoma showing thymic-like elements (CASTLE) is a rare tumour of the thyroid of thymic origin. The histological appearance of this tumour may be similar to that of squamous cell carcinoma of the thyroid, but outcome associated with CASTLE is more favourable.

A systematic literature review was conducted for case reports on CASTLE. A text word search of the Medline database was made with a manual search of the citations from these references. Twenty-two case reports were found.

In five patients with tumour-negative lymph nodes no local or distant recurrence was observed. Seventeen patients had unknown or involved lymph nodes. Two patients were excluded from further study: one had no follow-up and one was treated by irradiation only. Of the remaining 15, six had local, three had distant and two had local and distant recurrence. In patients with involved or unknown lymph node status, local recurrence was noted in one of five patients treated by surgery and irradiation, and in seven of ten patients treated by surgery alone. Irradiation or systemic chemotherapy was given to four patients with recurrent tumours, with variable response.

CASTLE with tumour-negative lymph nodes has a low risk of recurrence and surgery without adjuvant therapy is sufficient. Radiotherapy seems indicated when lymph nodes are tumour positive and can be effective for recurrent tumours. In selected patients surgery for recurrent tumour can improve quality of life and outcome.