Light micrograph (LM) of a biopsy sample showing adenocarcinoma cells. An adenocarcinoma is a cancer arising from glandular tissue. Many of these cells have large, irregular, rapidly dividing nuclei (dark blue). The large cell at lower right has its nucleus moved to one side by a large vacuole. These cells are known as "signet cells", from their resemblance to signet rings. Carcinomas can be treated by chemotherapy and radiotherapy, or by surgery if they have not spread. Most are fatal.