Metastatic RCC with worsening pain Again noted is a large destructive enhancing mass of the right sacrum consistent with known metastatic disease. The mass is centered in the sacral wing which involves S1-S3 and crosses the sacroiliac joint to involve a small portion of the right ilium. The mass also extends into the left sacral wing with focal involvement of the left ilium. Additionally, there is soft tissue involvement anterior to the sacrum with signal abnormalities noted within the piriformis muscle. The mass obliterates the right S1 and S2 neural foramen and partially invades the right S3 neural foramen and sacral canal. It is difficult to determine if there has been slight interval increase due to technical differences between MR and CT but overall the mass appears similar in extent. It measures approximately 13 cm in the greatest transverse dimension and approximately 10 cm in the greatest craniocaudal dimension.Multiple other lesions noted throughout the pelvis with the next largest present in the left posterior acetabulum/ischium, measuring approximately 2.3 x 3.8 cm. Additional foci of disease are noted in the left iliac wing (series 8 image 7/50), the L5 vertebral body (series 8 image 9/50), the left superior acetabulum (series 8 image 24/50) and the subtrochanteric portion of the left femur (series 8 image 42/50).There is severe degenerative disc disease of the lower lumbar spine.
Metastatic disease within the bones of the pelvis, left proximal femur, and lower lumbar spine as described above. The largest mass within the right sacrum appears comparable to the prior CT exam although direct comparison is limited given technical differences between MRI and CT.