Tumor-to-Tumor Metastasis: Lung Carcinoma Metastasizing to Thyroid Neoplasms

Figure 2

(a) Within the papillary carcinoma is an abrupt transition to a morphologically distinct neoplasm (magnification ×40). (b) Metastatic carcinoma is arranged in nests with large nuclei, nucleoli, and abundant clear-to-eosinophilic cytoplasm (magnification ×200). (c) Napsin-A is shown to be positive in the metastatic carcinoma (magnification ×200). (d) Thyroglobulin is negative in the metastatic carcinoma, while being strongly positive in papillary carcinoma (magnification ×100).

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