Parachordoma: a new clinicopathologic entity.

Parachordoma is a tumor that was established and described by Laskowski in 1951. It is a rare tumor, which appears adjacent to tendons, synovium, and even osseous structures. It is lobular and pseudoencapsulated. Histologically, in some ways, it is compatible with the chordomas of bone with a constant fibrous tissue component. It grows slowly and is only locally invasive. If not adequately excised, it is prone to recur, but complete surgical removal is usually possible. Its exact histogenesis remains obscure. This tumor may have some relationship to the great vesicular cells of chordoid tissue described by Schaffer as "blasige Zellen von chordoiden Gewebe" developing from special synovial cells. Ten cases collected over a period of 26 years at the Institute of Oncology in Warsaw are presented.