Metastatic Merkel cell carcinoma with positive expression of thyroid transcription factor-1--a case report.

Abstract: We report on a case of metastatic Merkel cell carcinoma in a 74-year-old patient with positive staining for thyroid transcription factor-1. This represents a new immunohistochemical staining pattern for Merkel cell carcinoma and has implications regarding the accurate diagnosis of this tumor type.