Renal lymphoma is most often seen in conjunction with multisystemic, disseminated lymphoma or as tumor recurrence. Renal lymphoma may also be seen in immunocompromised patients or, rarely, as primary disease.
Computed tomography (CT) is a sensitive, efficient, and comprehensive examination for evaluation of the kidneys in patients with suspected renal lymphoma. Lesions can be solitary masses or multiple masses. They are generally bilateral and present extension by contiguity diffuse infiltration or perirenal involvement. Radiological findings frequently indicate renal involvement with multiple nodules and help in clarifying the diagnosis when considered along with previous family history. Renal lymphoma generally is presented as a bilateral nodular infiltration with a diffuse kidney increase and infiltration of the renal parenchyma by a diffuse invasion of the retroperitoneum.
When the mass measures 20 HU or greater at the unenhanced CT examination, it may represent a high-attenuating cyst or a solid renal neoplasm. Usually, a difference of 10 HU was suggested as evidence of enhancement between precontrast and post contrast scans.
On CT scanning, the criteria for the diagnosis of a simple cyst include sharp margination and demarcation from surrounding renal parenchyma, smooth thin imperceptible wall, water density content with Hounsfield units ranging from 0 to 20 without enhancement following intravenous administration of contrast material.
Now although it is likely that this is a benign cyst but with your family history and slightly complex echopattern on ultrasound even though CT is pointing towards a benign cause, a follow up is definitely required after discussing with your urologist. Lymphoma is known to mimic cysts at times.
But to find it only in the kidney without significant systemic involvement with CT findings more or less benign, the only worrying factors remain a strong family history and complex appearance on ultrasound. Follow up is advisable in conjunction with your urologist. Ultrasound guided FNAC may also be an option.
thank you for answering so quickly i have one more question is an attenuation value of 17-18 hu seen often in non complicated cysts