Typical metastases, atypical course of the disease and morphology

Abstract

The process of tumor differentiation is a central aspect of the histopathological classification of solid malignancies and is closely related to the biological behavior of the tumor (poorly differentiated tumors/dedifferentiated tumors are known to be more aggressive than more differentiated tumors). The mechanisms by which tumor cell differentiation is disrupted are poorly understood, but pathologists and molecular tumor biologists have introduced the concept of dedifferentiation to explain the phenotypic changes that occur in solid tumors. In this review, we discuss a case of detection of dedifferentiated cancer, where even with the help of molecular testing of a tumor sample, we were not completely able to unambiguously determine the original source of the process, which entailed difficulties in choosing treatment tactics. And the main question that we asked ourselves during the treatment process: should treatment be based on molecular markers identified in the tumor, or should treatment be carried out according to the recommendations for the treatment of tumors of an undetected primary location with empirically selected chemotherapy?