Fibrous histiocytoma: an analysis of the storiform pattern.

A storiform pattern is an important structural feature of fibrous histiocytoma (FH). In this analysis reconstructions of histological patterns were carried out from drawings. Highly FH with only a suggestion of storiform pattern and small star-formations were seen, there were other lesions with more pronounced fiber formation which showed more distinct and larger storiform stars. These structures can frequently be followed for only 3 sections of 5 micron thickness. In contrast to leiomyomas or meningioma, no regular or consistent orientation of these structures with respect to vessels is evident. Storiform structures apparently develop at the periphery of adjacent proliferating cells groups. They show a typical and diagnostically significant histological pattern, which was found to some degree in all FH examined.