MULTIPLE OSTEOMAS IN MICE

Osteomas (dense compact neoplasms of mature bone tissue) are rare in n early all strains and stocks of mice. Of 224 Him:OF1 mice maintained u ntil natural death or until terminally ill, 116 (51.8%) had one or mor e osteomas. Osteomas had a predilection for the skull and the larger b ones of the limbs. Plasma alkaline phosphatase concentrations were ele vated significantly in osteoma-bearing mice (446 +/- 153 U/liter versu s 206 +/- 65 U/liter in age-matched controls without osteomas). Only v ery large osteomas resulted in clinical signs, and longevity was not s hortened. Histologic examination showed clearly separated dense bony t issue irregularly arranged and forming a mosaic pattern, with distinct cement lines and medullary spaces filled with fibroreticular connecti ve tissue. Electron microscopic examination revealed virus-like struct ures in osteoblasts, osteocytes, and fibroblasts and in the place of r emnants of necrotic cells.