Medullary and papillary tumors are frequently associated in the same thyroid gland without evidence of reciprocal influence in their biologic behavior

Papillary thyroid microcarcinoma (mPTC), is a very frequent incidental finding with a frequency varying from a few percent to 35% at postmortem histopathologic examinations. However, the presence of mPTC in patients undergoing thyroidectomy for multinodular goiter (MNG) and for Graves' disease (GD) has been found to be lower. Patients with medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) association have been published as anecdotal case reports, as well as kindred with familial MTC or multiple endocrine neoplasia (MEN) 2A with some members simultaneously affected by MTC and PTC. We studied the prevalence and the biological behavior of MTC associated with PTC, with particular attention to those cases in which a mPTC was incidentally found. Twenty-seven of 196 (13.8%) MTC cases showed an association with PTC and in particular 21 of 190 (11.05%) with an incidental mPTC. This percentage is higher than that reported in the literature on the association of mPTC with GD (2.8%-4.5%) and MNG (3%). Also the percentage of the more general association of MTC/PTC, not restricted to mPTC, found in our series (13.8%) is higher than that reported in studies that analyzed the prevalence of PTC (any size) in patients treated for MNG (7.5%). A similarly high percentage of MTC/PTC had not been reported before and in particular there are no reports on large series of MTC/PTC. We also analyzed the epidemiologic, clinical, and pathologic features of MTC associated and not associated with PTC without finding any difference. In particular the outcome of the MTC did not appear to be influenced by the presence of the PTC and the specific radioiodine treatments. Moreover, although we cannot completely exclude a shared pathogenic event as the cause of both MTC and PTC, the molecular analysis of RET gene alterations did not show any common mutatio

Simultaneous occurrence of medullary and papillary thyroid microcarcinomas: a case series and review of the literature

<p>Abstract</p> <p>Introduction</p> <p>Papillary thyroid microcarcinoma has been demonstrated to present in association with medullary thyroid carcinoma, however, medullary thyroid carcinoma and papillary thyroid carcinoma represent rare entities. In recent years this rarity has been increasingly observed. The pathogenesis is still controversial. Genetic analysis of <it>RET</it> proto-oncogenes in cases of simultaneous papillary thyroid carcinoma and medullary thyroid carcinoma has so far provided conflicting results; although it seems that germline mutations play a potential role in the development of both histological types.</p> <p>Case presentations</p> <p>This paper describes four rare cases of simultaneous medullary thyroid carcinoma and papillary thyroid microcarcinoma with unique features:</p> <p>Case one was a 43-year-old Jewish woman, born in Israel, daughter of a Latvian immigrant mother and a father born in Israel. Case two was a 44-year-old Arab woman born in Israel. Case three was a 45-year-old Jewish woman, born in Israel, daughter of Moroccan immigrant parents and is unique for the presence of lymph node metastatic medullary thyroid carcinoma, and one lymph node with metastatic papillary carcinoma found in the same side. Case four was a 77-year-old Jewish woman, born in Iraq. These cases are unique in their composition of thyroid carcinoma, consisting of histologic features of medullary thyroid carcinoma, papillary thyroid microcarcinoma, and follicular thyroid adenoma. The four cases represent different ethnicity groups that live in north Israel, and case four is notable for the advanced age of the patient (77 years).</p> <p>Conclusion</p> <p>These four cases add more data supporting the coincidental coexistence of papillary thyroid microcarcinoma and medullary thyroid carcinoma; our results may suggest that the simultaneous occurrence of medullary thyroid carcinoma and papillary thyroid microcarcinoma is generally a simple reflection of this coincidence. Endocrinologists and pathologists should be aware of this entity. The pathologist can play a pivotal role in identifying papillary thyroid microcarcinoma in concurrent existence with medullary thyroid carcinoma.</p