Epstein-Barr Virus-Associated Smooth Muscle Tumour: A Case Series with a Significant Proportion of Tumours Showing Proclivity for Cutaneous Soft Tissues

Background: Epstein-Barr virus-associated smooth muscle tumours (EBV-SMTs) are rare neoplasms of uncertain biological potential. They are seen in the setting of immune suppression from a variety of causes, including HIV infection and post-transplant immunosuppression. Most of the literature pertaining to these neoplasms comprises case reports and small case series, with a dearth of documented cases from South Africa. Objective: To expand on the literature of these rare neoplasms in the South African context, with an emphasis on a subset showing a predilection for the cutaneous soft tissues. Method: Twenty-one EBV-SMTs from 19 consecutive patients were retrieved from the archives of the Division of Anatomical Pathology in the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, and the National Health Laboratory Service. Clinical and pathological characteristics of each case were recorded, including patient age, tumour site, H&E morphology, immunophenotypic features and the tumoural EBV status. Results: The patients’ ages ranged from 12 to 63 years, with a mean of 36 years. Thirteen (68%) of the patients in whom the HIV status was known were HIV-positive. Two of the 19 patients each had 2 tumours, thus accounting for the total of 21 neoplasms studied. Although 12 of the 21 tumours (57.1%) were from a variety of visceral organs, 9 (42.9%) originated in the dermis and superficial subcutaneous tissues, making the cutaneous soft tissues the most commonly affected site. Morphologically, all of the neoplasms were characterised by fascicles of myoid cells, admixed rounder tumour cells, scattered intratumoural lymphocytes and variable immunohistochemical staining with markers of smooth muscle differentiation. All 21 neoplasms were proven to harbour EBV DNA. Conclusion: A significant proportion of EBV-SMTs may present in the cutaneous soft tissues. This neoplasm should, therefore, be included in the histopathological differential diagnosis of any cutaneous or superficial subcutaneous spindle cell tumour, especially in patients with a history of underlying immune suppression. Accurate diagnosis thereof and its distinction from other spindle cell neoplasms is important in view of management implications and the potential for multicentricity in some patients.