[Carcinoma-in-carcinoma metastasis. In situ DNA quantification and immunohistochemical diagnosis].

In the rare event of cancer-to-cancer metastasis, one malignant neoplasm spreads to a second carcinoma. To date, 42 such cases have been published in the English- and German-language literature. We report two additional patients, each with metastatic bronchial cancer present in a renal carcinoma. In addition to immunohistochemical examinations, we performed in situ DNA image cytometry of histologic preparations as a novel analytical technique to differentiate metastatic tissue from the host tumor. In both cases DNA histograms of metastatic tumor resembled those of the primary malignancy but were clearly dissimilar to the host tumor. In 70% of previously reported cases renal carcinoma was the host tumor while in 50%, cancer of the lung was the most frequent donor tumor.