Coexistence of medullary thyroid carcinoma and recurrent non-functional pituitary adenoma: a case report

BACKGROUND: Medullary thyroid carcinoma and pituitary adenoma are neuroendocrine tumors and their coexistence has not been reported in the literature, previously. Medullary thyroid carcinoma is a neoplasm of the thyroid gland arising from parafollicular c-cells producing calcitonin, and pituitary adenoma is a benign hyperplasia of the cells of the pituitary gland. Coexistence of these neoplasms can be explained by being affected by simultaneous primary neoplasms or tumor-to-tumor metastasis phenomenon. CASE PRESENTATION: We present the case of a 60-year-old Persian man who presented to the clinic with a chief complaint of headache for the last 2 months. His past medical history was significant for non-functional pituitary macroadenoma and medullary thyroid carcinoma and he had received a total thyroidectomy and a transsphenoidal surgery several years ago. Diagnostic evaluations revealed that the pituitary adenoma has recurred. He was well and symptom-free after the second transsphenoidal surgery for resection of the adenoma. Noticeably, investigations were negative for any form of multiple endocrine neoplasia syndromes; however, we could not rule them out definitively. CONCLUSIONS: To the best of our knowledge, it is the first case reported in the literature of a patient who has been affected by recurrent non-functional pituitary adenoma and medullary thyroid carcinoma, concomitantly. Although this association can be accidental, it emphasizes the fact that patients with a history of a neoplasm should be monitored regularly in order to diagnose and treat possible second primary cancers in a timely manner. Of note, this consideration is of great importance in patients whose first neoplasms have better prognosis and survival rates, which provide them more time to develop second primary cancers, for example, pituitary adenoma.