The significance of sinonasal radiodensities: ossification, calcification, or residual bone?

PURPOSE To determine whether very radiodense material within a sinonasal soft-tissue mass on CT can be differentiated as calcification, ossification, or residual bone. METHODS We retrospectively described the radiodensities within 235 sinonasal soft-tissue masses as discrete, solitary or multiple, or as a diffuse process with either a well-defined or poorly defined margin. They were also classified as calcification, ossification, or residual bone. Findings were correlated with pathologic specimens. RESULTS Residual bone was underdiagnosed; calcification was overdiagnosed. A solitary discrete density was most likely to be calcification within an inflammatory mass. However, multiple discrete densities were as likely to be in a tumor as in an inflammatory lesion. If the process was diffuse with a well-defined margin, it was most likely to be a benign fibroosseous lesion. If the process was diffuse with a poorly defined margin, it was most likely to be a high-grade sarcoma. Densities within inverted papillomas were shown to be residual bone, not calcifications; densities within esthesioneuroblastomas were calcifications. CONCLUSION Radiodensities may help in refining a CT diagnosis, but one may not know based on CT whether the density is a calcification, ossification, or residual bone.