Abstract
Introduction: Papillary tumors are the most common while medullary thyroid cancer (MTC) is the third most common of all thyroid cancers. We report a case of papillary thyroid carcinoma (PTC) in the right thyroid lobe together with coexistent MTC and PTC in the left thyroid lobe clearly separated from each other. Thyroid tumors with mixed histologic characteristics are more common while cases with separated foci of differently originated tumors -like our case- are very rare. Case: A 44-year-old woman having right lobe total, left lobe subtotal thyroidectomy regarding multinodular goitre was histologically diagnosed with PTC in the right thyroid lobe and, PTC beside a tumoral area considered suspicious MTC in the left thyroid lobe. After being refferred to our hospital for further evaluation, immunohistochemically the suspected tumoral area in the left thyroid lobe was idendified as MTC presenting side by side PTC. Microscopic and immunohistochemical features of two thyroid carcinoma types were observed in distinct locations clearly separated by non-neoplastic thyroid parenchyma (NNT)(Fig-1). Postoperative ultrasound examination showed two lymph nodes in the right anterior cervical area of the neck and needle aspiration biopsy revealed the presence of PTC metastasis. Complementary thyroidectomy, central neck dissection and right modified neck dissection were performed with subsequent Iodine-131 ablation therapy.
Discussion: It is questionable how two tumor types deriving from different embriogenic tissues can develop simultaneously in the same patient. Several hypothesis have been advanced in the literature like those – a common stem cell that gives rise to both parafolliculer C-cells and folliculer epithelial cells; a common tumoroginetic stimulus triggering neoplastic transformation of both cell lines. There is no common mutation known to be involved in the pathogenesis of the two tumor. types. A mere coincidence seems to be the fact in our case.