Psammoma body

In the field of pathology, a psammoma body is a round, collection of calcium, seen microscopically. The term is derived from the Greek word psammos meaning "sand." Psammoma bodies are commonly seen in certain tumors such as papillary thyroid carcinoma, serous papillary ovarian adenocarcinoma, endometrial adenocarcinomas, and meningiomas. Psammoma bodies have a laminar appearance. The origin of psammoma bodies is controversial, but one theory is that the nidus for their formation is a single necrotic tumor cell, upon which layers upon layers of calcium salt deposits are added.