A clinicopathological study of Epstein-Barr virus positive (EBV+) smooth muscle tumours (SMT) in adult renal transplant recipients

Abstract

9064 Background: EBV+ SMT is a rare tumour in immunocompromised individuals. We present the clinicopathological characteristics of EBV+ SMT in 8 adult renal allograft recipients in arguably the largest reported single series. Methods: From the SGH renal transplant registry from 1989 to 2004, 8 EBV+ SMT cases and their histopathology were re-evaluated for diagnostic confirmation. Results: The total number of renal transplant patients in this 15 year period was 667 with 88 patients diagnosed with cancer. EBV+ SMT was higher in incidence (7.4%) than post-transplant lymphoproliferative disease (PTLD) (5.6%). Five patients were male, 3 female, all were Chinese, with a median age of 42 years (29 - 61 years). Median time-to-EBV+SMT diagnosis from renal transplant was 6 years. Four patients were symptomatic at diagnosis and 6 had multiple sites of tumour at presentation including larynx, pharynx, duodenum, lung, breast, liver, spleen, bladder, bone, kidney and adrenal glands. Four are alive with a median survival of 41 months, but no deaths were EBV+SMT-related. The EBV+SMT were indolent in behaviour and tapering of immunosuppression for all patients yielded no objective responses. One patient with biopsy-proven multiple EBV+SMT liver nodules that progressed on immunosuppression taper was treated with rapamycin with durable complete radiological regression. The morphological features of all 8 patient tumour specimens show smooth muscle differentiation. EBV encoded RNA in-situ hybridisation (EBER-ISH) and Epstein-Barr Nuclear Antigen-2 (EBNA-2) were positive in all patients. By IHC, smooth muscle actin (SMA) was strongly positive in all patients and desmin-positive in 6 patients. Immunohistochemistry staining in all 8 patients was negative for CD21, bcl-2 and weakly detectable for Ki-67. Conclusion: The comparably high incidence of EBV+SMT in immunosuppresed patients with a Chinese predominance suggests there may be an ethnic/geographical predisposition such as with nasopharyngeal cancer. Rapamycin may be a potential therapy for EBV+SMT. No significant financial relationships to disclose.