PMC5133398_01
(A-E): Calcitonin-negative primary neuroendocrine tumor of the thyroid (CNNET). (A): CNNET aspect during surgery with invasion to esophagus (Es) and sternothyroid muscle (STM); T: trachea. (B): Right thyroid lobe (necropsy); notice the whitish, mottled look. (C): CNNET microscopic aspect with hematoxylin and eosin staining (H-E). Bar = 50microm. (D): CNNET immunohistochemical positive staining for cytokeratin (CK AE1-AE3). Bar = 200microm. (D1): CK AE1-AE3 positive control (Liver tissue). (D2): CK AE1-AE3 negative control (Liver tissue). (E): CNNET immunohistochemical positive staining for synaptophysin (Syn). Bar = 50microm. (E1): Syn positive control (medullar thyroid carcinoma). (E2): Syn negative control (thyroid follicular cells).
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No evidence of invasion to the regional lymph node was detected (Fig. 1A). The right thyroid lobe, with preserved shape and size, displayed several whitish foci, which were firm when dissected (Fig. 1B) and histopathological examinations revealed similar features to those of the thyroid tumor located in the left lobe. The cells were arranged in the form of solid nests supported in by a moderate fibrovascular stroma (Fig. 1C). The cytoplasm of tumor cells (20 % of the field) was moderately positive for CK AE1-AE3 (Fig. 1D), whereas 100 % of the cells were intensely positive for Syn (Fig. 1E). "With the exception of a few healthy follicles trapped in neoplasia," it stained negative for
(A): CNNET immunohistochemical negative staining for thyroglobulin (Tg); thyroid follicle trapped in neoplasia with positive staining for Tg (arrow). (A1): Tg positive control (Thyroid follicular cells). (A2): Tg negative control (Thyroid parafollicular cells-medullar thyroid carcinoma). (B): Immunohistochemical negative staining for calcitonin (CT). (B1): CT positive control (medullary thyroid carcinoma). (B2): CT negative control (thyroid follicular cells). (C): Nuclear antigen Ki-67 staining in tumor cells with the monoclonal antibody MIB I (arrow); proliferation index of 3%. Bar=50microm.
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Tg (Fig. 2A), CT (Fig. 2B), CEA and S100. The determination of the nuclear antigen Ki-67 was 3%, which is deemed as low (Fig. 2C).