Diagnosis of the Primary Tumor Site in the Case of Liver Metastatic Carcinoma

Immunohistochemical markers have been frequently utilized as a diagnostic tool in pathology to help in diagnosing malignancy of unknown primary sites. In previous cases, the immunohistological expression of cytokeratin 7 (CK7), Napsin A, and thyroid transcription factor-1 (TTF-1) has helped identify and diagnose primary malignancy as originating from the lung. This case report describes an elderly woman with a liver metastasis consistent with a lung primary and illustrates the utility and importance of tissue-specific markers as a diagnostic tool in the evaluation of unknown primary tumors.