IntroductionImmunodeficient patients, including the recipients of solid organs, exhibit an increase in the incidence of neoplasms. Post-transplant smooth muscle tumor (PTSMT) is a distinct and infrequent entity of these groups of neoplasms. Epstein–Barr virus (EBV) is considered to be involved in the etiology of this neoplasm.Case reportA 28-year-old man who underwent liver transplantation presented with abdominal pain and diarrhea for several months. He had a history of resistant systemic

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... egalovirus (CMV) infection after transplantation. On physical examination, he had mild abdominal tenderness. Spiral chest and abdominopelvic CT scan with contrast showed a liver lesion with ring enhancement; furthermore, it showed a solid lesion in the spleen and multiple small lesions in lower lobes of both lungs. Colonoscopy revealed multiple small raised polypoid lesions throughout the rectum and colon. Microscopic evaluation of colon mucosa biopsy using IHC study was in favor of spindle cell neoplasm with high proliferative index. He underwent a right hemicolectomy. A microscopic study showed spindle cell proliferation with mild atypia and a mild increase in mitotic rate without any necrosis, with features of smooth muscle tumor. Trucut biopsy of liver mass was also in favor of smooth muscle tumor. According to transplantation history and considering the possibility of EBV-associated smooth muscle tumor, EBV encoded RNA (EBER) chromogenic in-situ hybridization (CISH) study on paraffin block of colon lesions was requested, which demonstrated EBV RNA in tumor cell nuclei and immunoblasts of the adjacent lymph node, suggesting EBV-associated smooth muscle tumor. In addition, PCR for CMV was requested on paraffin block of the colon lesions, which also showed a positive result. PCR for EBV and CMV viremia were negative. The dosage of immunosuppressive agents was reduced, and currently, he is being followed, with slow expansion in the size of the lesions.Conclusion Although the incidence of post-transplant smooth muscle tumors (PTSMTs) is low, it should be remained in the differential diagnosis in post-transplantation patients, especially dealing with multifocal tumors. As strong stimulant for smooth muscle tumors, close follow-up and screening for EBV and CMV infection and early treatment at the time of diagnosis are recommended to avoid these virus-induced tumors.