⁹⁰Y-TheraSpheres: The New Look of Yttrium-90

Selective internal radiation therapy with ⁹⁰Y-TheraSphere or ⁹⁰Y-SIRSphere is used in the treatment of unresectable hepatic malignancies. To the best of our knowledge, this is the first ⁹⁰Y-TheraSpheres series. BTG International Canada Inc. provided nonradiated microspheres from the Nordion manufacturer. The histologic processed microspheres were colorless, refractile, polarizable, 20 to 30 μm in diameter, and an occasional internal bulls'-eye seen with the condenser out and an internal cross seen with polarized light. Identical microspheres were identified in 15 hepatectomy specimens from four centers between February 2016 and March 2018. The patients were usually male (male=10, female=5) with a mean age of 59 years. All patients had a prior diagnosis of hepatocellular carcinoma (HCC) and documented ⁹⁰Y-TheraSphere (mean duration from last deployment=32 wk). All surgical pathology specimens in these 15 patients were reviewed, but the microspheres were only identified in the hepatectomy specimens. During manuscript preparation, one case of ⁹⁰Y-TheraSpheres gastritis was prospectively identified from a separate patient with a history of HCC and ⁹⁰Y-TheraSpheres. In conclusion, recognition of ⁹⁰Y-TheraSpheres is important so that one may consider the possibility of a nearby malignancy and or establish the cause of the background inflammatory or radiation-related injury. These structures can be easy to miss because the subtle morphology is distinct from previously reported ⁹⁰Y-SIRSphere. Clues to the diagnosis include a history of HCC and background radiation change. We report the characteristic morphology as microspheres that overlap in size with ⁹⁰Y-SIRSphere, but can be differentiated based on ⁹⁰Y-TheraSpheres' colorless appearance with occasional internal bulls'-eyes with the condenser out and an internal cross with polarized light.