Technique: Multiplanar multisequence imaging including contrast enhanced images.
Findings: There is transitional lumbosacral anatomy, and the highest complete sacral level has been designated S1. There is clearly an abnormal marrow infiltrate in the left half of the S1, extending medially to reach the midline and extending superiorly into the left transverse process of L5 and inferiorly into S2 ala. Extraosseous extension involves the left S1 posterior foramina, and the interosseous portion of the upper sacroiliac joints. There are abnormal left common and external hilar lymph nodes consistent with lymphoma. No sacroiliitis.
Conclusion: Findings compatible with lymphoma involving the sacrum. The extent of disease appears slightly greater than demonstrated on the PET scan. This is straightforward to biopsy under CT guidance, if required.