However, immature bone is not well organized and may be more difficult to discriminate from calcifications. Mature bone shows fatty bone marrow within trabecular spaces on both CT and MRI. Therefore, it is important to correlate MRI with other imaging modalities (including radiography, CT, and ultrasound) when available. Nevertheless, calcifications may still be overlooked on MRI, particularly when small and surrounded by other low-signal-intensity structures such as tendons, ligaments, and fibrosis. Phase images from susceptibility-weighted imaging may also allow for a better distinction between calcifications and other causes of susceptibility variations.
Sensitivity for the detection of small calcifications may be improved by using gradient echo and susceptibility-weighted imaging. Calcifications usually demonstrate uniformly low signal intensity on all MRI sequences. On ultrasound, it may be difficult to distinguish between calcifications and ossification, especially when acoustic shadowing is present. Hounsfield unit (HU) values for calcifications show a wide range (usually between 100 and 400), whereas bone reaches higher HU values (700 for trabecular bone and > 1500 HU for cortical bone. CT is more sensitive in detecting calcifications and ossification. Calcifications normally appear as mineralized densities, whereas mature bone shows an outer cortex and inner trabecular pattern (Fig. Radiography is usually the initial imaging modality by which soft tissue calcifications and ossification are detected. Subsequently, we review the clinical presentations, locations, imaging characteristics, and differential diagnostic considerations of several benign entities with calcifications or ossifications that may simulate malignancy.ĭifferentiation between calcifications and ossification is very important in making the correct (differential) diagnosis. We first discuss how soft tissue calcifications can be differentiated from ossification on imaging. The purpose of this article is to review calcified or ossified benign soft tissue lesions that may simulate malignancy. In addition, differentiating between calcification and ossification can narrow the differential diagnosis as some pathologies tend to produce ossifications while other pathologies tend to produce calcifications. The identification of calcifications or ossification in a soft tissue lesion is important because it can narrow the differential diagnosis or be suggestive of a certain diagnosis when combined with other imaging findings. It is the task of the radiologist to differentiate lesions that are certainly benign from those that are not, and to provide a differential diagnosis for lesions that appear malignant or are of unclear nature in terms of benignancy or malignancy on imaging. Malignant soft tissue lesions are rare, but they are potentially life-threatening and may pose a diagnostic and therapeutic challenge. The vast majority of soft tissue lesions are benign, with a very good outcome after resection. Many patients are referred to the radiology department for evaluation of a soft tissue lesion in daily practice.
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