RADIOLOGY: ABDOMEN: Case# 32911: NHL-SMALL CLEAVED. This is a sixty-five year old male with a history of non Hodgkins lymphoma which was diagnosed recently after percutaneous ultrasound guided biopsy of the retroperitoneal soft tissue mass. A large lobulated retroperitoneal soft tissue mass is seen starting at the level of the bifurcation of the aorta, extending down into the left abdomen and left side of the pelvis, and measuring approximately 12 x 12 x 13.5cm in its transverse, anterior-posterior and craniocaudal dimensions. The mass is seen encasing the left common iliac, internal iliac as well external iliac vessels. The left ureter is also encased by this mass causing proximal dilatation. In addition, discrete left obturator node is seen measuring 3 x 4cm . Another discrete left paraaortic node above the bifurcation is noted measuring 3 x 4cm. Multiple small nodes are noted in the peri-diaphragmatic region anteriorly. There is mild left hydroureteronephrosis secondary to encasement of the left mid ureter by the mass. Delayed scout image demonstrates excretion bilaterally, with moderate dilatation of the left collecting system down to the mass. There is minimal thickening of the left Lateroconal and Gerotas fascia. Multiple small approximately 1cm lymph nodes are noted in the left side of the neck in the level five and level two . No significant lymph node enlargement elsewhere in the neck. Non-Hodgkins Lymphoma is a mixed group of diseases comprising 60-80% of all lymphomas. It is common in immunosuppressed patients. Non-contiguous spread and involvement of the GI tract are characteristic with 50% of patients having abdominal adenopathy on presentation, 40% spleen involvement, and 14% liver involvement. The most common finding on CT is adenopathy with conglomeration of enlarged nodes to form multilobular masses which encase vessels, displace organs, and obstruct ureters. The accuracy of CT in detecting lymphoma ranges from 68-100%*. False positives usually result from confusion with unopacified bowel loops or normal vascular structures and misinterpretation of lymphadenopathy due to benign inflammatory disease as malignancy. False negatives result from an inability to recognize replaced but normal-size or minimally enlarged lymph nodes as abnormal.