Final Diagnosis --EBV-associated smooth muscle tumor


EBV-associated smooth muscle tumor


EBV-associated smooth muscle tumors are a rare entity seen with different forms of immunodeficiency. This case highlights that PT-SMT can grow distant from the transplanted organ. PT-SMT appears to occur more frequently in kidney transplant recipients followed by heart/lung and liver. The liver (native and allograft) appears to be preferentially involved by PT-SMT followed by lungs and airways, gut and spleen with less common involvement of the kidneys, central nervous system and adrenals. In contrast, SMT associated with HIV has a predilection for the central nervous system and has also been reported in the gut, liver, adrenals, lungs and upper airways. About 50% of patients with PT-SMT will show multiple tumors (Deyrup et al., 2006; Hussein et al., 2014). Morphologically, these tumors are variably sized with smaller lesions centered around small vessels. Tumors consist of well differentiated spindled smooth muscle cells arranged in short fascicles with elongated cigar shaped nuclei and eosinophilic cytoplasm. Mitotically, these tumors tend to show <3 mitoses per 10 HPF. Rarely, some tumors will look frankly sarcomatous or will show increased mitotic activity and necrosis. Cuffing and tumor infiltrating lymphocytes are frequently seen. These lymphocytes are predominantly CD3 positive T-cells. A characteristic feature is the presence of areas with primitive round cell morphology, which can be seen to a varying degree ranging from nodules with a minority of primitive cells to nodules composed entirely of them. Sarcomatous features, frequent mitosis and necrosis are more commonly seen with HIV associated SMT than with PT-SMT. Variants described in HIV-SMT such as angioleiomyoma and myopericytoma are not reported in PT-SMT. Unlike conventional leiomyomas and leiomyosarcomas, morphologic features do not predict survival and it has been proposed to use the term smooth muscle tumors of uncertain potential (Dekate & Chetty, 2016; Hussein et al., 2014). Differentiating somatic smooth muscle tumors from EBV-SMT can be done by detecting the virus in tumor cells. Many techniques can be used such as PCR, LMP1 immunocytochemistry or EBER in-situ hybridization (Jonigk et al., 2013). Treatment generally consists of surgical resection and adjustment of immunosuppression for PT-SMT. Antiretroviral therapy is employed in patients with HIV associated SMT.


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Mohamed El Hag, MD and Michael Nalesnik, MD

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