title: Mixed medullary-papillary carcinoma of the thyroid: report of two cases and review of the literature.
abstract: Papillary thyroid carcinoma (PTC) and medullary thyroid carcinoma (MTC) are two distinct types of thyroid carcinoma with considerable difference in terms of cellular origin, histopathological appearance, clinical course and prevalence. The histogenetic origin and possible molecular mechanisms responsible for the development of mixed medullary-papillary carcinoma of the thyroid are still unclear. The most widely accepted hypotheses considering co-occurrence of MTC and PTC are stem cell theory, collision effect theory and hostage theory. Herein we describe two rare cases of mixed medullary-papillary thyroid carcinoma with co-occurrence of MTC and PTC which developed with concomitant MEN 2A and different sites of lymph node metastasis in the first patient, while with atypical clinical presentation in the second patient. In conclusion, co-expression of thyroglobulin, synaptophysin and chromogranin by the papillary component of mixed tumor seems to support stem cell theory in our first case, whereas positive staining for calcitonin but not for thyroglobulin in the medullary component of the tumor along with separation of these two tumors from each other by a normal thyroid tissue seem to indicates the likelihood of collision effect theory in our second case.
authors.affiliation: Department of Endocrinology and Metabolism, Faculty of Medicine, Kocaeli University, Kocaeli, Turkey.
authors.forename: Eren
authors.initials: E
authors.lastname: Gurkan
authors.forename: Yesim
authors.initials: Y
authors.lastname: Gurbuz
authors.forename: Ilhan
authors.initials: I
authors.lastname: Tarkun
authors.forename: Zeynep
authors.initials: Z
authors.lastname: Canturk
authors.forename: Berrin
authors.initials: B
authors.lastname: Cetinarslan
mesh_terms: D000328:Adult; D000368:Aged; D002116:Calcitonin / Q000096:biosynthesis; D002277:Carcinoma / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000235:genetics; D018278:Carcinoma, Neuroendocrine; D002291:Carcinoma, Papillary; D053379:Chromogranin A / Q000096:biosynthesis; D006801:Humans; D008175:Lung Neoplasms / Q000556:secondary; D008207:Lymphatic Metastasis; D008297:Male; D018813:Multiple Endocrine Neoplasia Type 2a / Q000175:diagnosis* / Q000000981:diagnostic imaging; D020641:Polymorphism, Single Nucleotide; D051096:Proto-Oncogene Proteins c-ret / Q000235:genetics*; D011859:Radiography; D016708:Synaptophysin / Q000096:biosynthesis; D013954:Thyroglobulin / Q000096:biosynthesis; D000077273:Thyroid Cancer, Papillary; D013961:Thyroid Gland / Q000473:pathology; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000235:genetics
chemical_list: D053379:Chromogranin A; D016708:Synaptophysin; D002116:Calcitonin; D013954:Thyroglobulin; D051096:Proto-Oncogene Proteins c-ret; C099282:RET protein, human