CASTLE tumour of the neck: a rare location of a malignant tumour of the thymus.

We present the case of a 62-year-old woman who consulted her physician in December 2005, suffering from a mass at the left lower anterior neck with rapid enlargement. Intraoperative frozen section was highly suspicious of a CASTLE tumour (carcinomas showing thymus-like differentiation). Finally, immunohistochemical investigation revealing positivity for CK5/6, c-kit (CD117) and CD5 as well as negativity for thyroglobulin, calcitonin, vimentin and TTF-1 confirmed the diagnosis. Due to lymph node metastases, radiochemotherapy was performed. Fifteen months after the initial diagnosis disseminated pulmonary metastases were found and treated with cisplatin based chemotherapy, which led to a stabilisation of the disease. In June 2008, computed tomography showed progress of the pulmonary metastases, making further chemotherapeutical treatment necessary. Although treatment was changed in October 2008, the staging evaluation in January 2009 revealed further progress of the metastatic disease. Currently, the patient is still alive, but receives no medical treatment at the moment.