Abstract
1) Osteomas are considered to arise from periosteal rests and through stimuli, and very rarely from cartilaginous rests.
2) The original collagenous fibers undergo fibromatoid development and then through intramembranous ossification develop into ssteomas in the following order. fibroma-ossifying fibroma, young form I-ossifying fibroma, young form IIossifying fibroma, mature-spongy osteoma-compact bone.
3) Two distinct stages in the development of young forms of ossifying fibromas are observed.
Form I. Osteoid tissue containing no bone cells, connective tissue with collagenous fibers, and giant cells from which osteoblasts are believed to arise, are chiefly observed.
The transitional processes, as shown by changes in the staining properties and morphology, in the development of collagenous fibers(Gel solution)from collagenous fibrils(Sol solution)to bone-like osteoid were evident in the specimens studied. The areas of Sol solution were transparant with Mallory, Elaast and v.Gieson stains but showed light red mucicarmin stained granules with P.A.S. reactions.
Form II. This type shows osseous tissue containing a few bone cells clustered in isolated islands, and is almost devoid of lamellar structure .The major portion of the tumor is occupied by connective tissue.
In the maturer forms of ossif f ing fibroma, trabeculae with lamellar formation of osseous tissue are seen and in the histologic slides taken from this series of cases approximately equal areas of connective and osseous tissues were observed
