Rebiopsy is considered an option for specific types of cancer, such as breast, non-small cell lung, and prostate cancer, in clinical trials and in practice. The benefit of rebiopsy comes from the selection of a new treatment strategy based on the genetic profile of the cells, which may reflect the development of drug resistance or hormonal changes. For colorectal cancer, the presence of different genomic mutations between the primary tumor and its metastases is rare, and rebiopsy is therefore not generally performed. The present study reports the case of a 68-year-old man who was initially diagnosed with metastatic adenocarcinoma from a primary colorectal cancer, but was subsequently rediagnosed with metastatic neuroendocrine carcinoma based on the pathological rebiopsy results. The patient responded well to cisplatin and etoposide treatment, after not responding to initial FOLFOX treatment. In this case, rebiopsy resulted in a change in treatment regimen and improved the patient's quality of life and his long-term survival. This case indicates that, when a colorectal cancer patient is unresponsive to standard treatment, it may be beneficial for the clinician to suspect an atypical histological type, and to consider rebiopsy.
Keywords: biopsy; colorectal cancer; neuroendocrine cancer.