Alteration in osteoblast cell number and cell activity in the presence of invading malignant fibrous histiocytoma

Correct prediction of tumor behavior and interpretation of local factors in the tumor microenvironment rely in part upon accurate determination of tissue changes after tumor invasion. The authors examined local bone changes in primary malignant fibrous histiocytoma (MFH) of bone in a 59-year-old woman. Three noninvolved and three tumor-involved sites were evaluated by quantitative determinations of bone structural and dynamic features. Compared to noninvolved sites, tumor-involved bone was characterized by significantly increased osteoblast index (89.4 ± 15.6 [mean ± SEM] versus 7.3 ± 6.0, P = 0.008), percent osteoid area (12.1 ± 2.7 versus 1.2 ± 0.5, P = 0.02), percent of trabecular surface covered by osteoid (70.0 ± 6.0 versus 14.5 ± 4.8, P = 0.002), and percent osteoid lined by osteoblasts (36.4 ± 3.6 versus 3.7 ± 3.0, P = 0.002). Bone 7.8 mm distant from invading tumor cells showed features characteristic of noninvolved sites, whereas bone completely surrounded by tumor showed markedly decreased osteoblast features. Osteoblast function also was affected by tumor; the amount of matrix laid down per day bore a significant positive correlation with the osteoblast index. These data indicate the following: (1) distinctive bone morphologic changes occur in situ during invasion by MFH; (2) changes affect aspects of bone formation but not resorption during invasion; (3) both osteoblast number and osteoblast activity are significantly altered; and (4) changes are local in nature and probably reflect the osteoblast response to local tumor factor(s) and are dependent upon the extent of tumor invasion. Cancer 59:755-760, 1987.