Klin Onkol 2018; 31(5): 366-370. DOI: 10.14735/amko2018366.
Background: The tumor-to-tumor metastasis is exclusively rare finding, in which one malignant neoplasia metastasizes to another tumor of different origin. Case: The author describes an 68-year-old woman, who was found to have a solitary tumor in the right kidney, as well as multiple tumor nodules in the liver. She underwent a radical nephrectomy. A histology of lesion in the kidney revealed a conventional clear cell renal cell carcinoma (RCC) harboring multiple metastatic foci of another adenocarcinoma. At that time, there was not possible to reliably specify a primary source. Subsequently, a probatory excision of tumor lesion in the liver was also done. A microscopy confirmed an adenocarcinoma with a similar appearance as found in RCC. Due to unfavourable health condition, a paliative chemotherapy could not be realized and the patient died shortly thereafter. A primary origin of adenocarcinoma remained unclear. Conclusion: A unique case of metastatic adenocarcinoma is described, that was initially diagnosed as an incidental finding within a clear cell RCC of the kidney. Such unexpected feature may represent a great diagnostic challenge for both, pathologist and clinician. From a prognostic point of view, an evidence of intratumoral cancer metastasis within a primary RCC is usually an indicator of disseminated oncologic disease with a poor outcome.
