2. Bilateral multiple nodules in lung: Epstein barr virus associated smooth muscle lesions

Abstract

Background Presence of multiple nodules in lung is concerning for metastatic tumour and triggers prompt evaluation. Such scenario in a transplant/immunocomprimsed patient is further complicated since infectious aetiology and secondary malignancy need to be considered. Epstein-Barr Virus (EBV) associated smooth muscle tumours are rare lesions that occur in immuno-comprimsed patients. They are typically well-differentiated with low mitotic activity and little cytological atypia. They are believed to represent consequence of multiple infection events rather than metastasis. Methods We report a 51-year-old patient with a history renal transplant and immunosuppression whose surveillance showed multiple bilateral lung nodules. Transthoracic, CT guided fine needle aspiration smears and core biopsy materials were evaluated using light microscopy, immunohistochemistry and in situ hybridisation for EBV associated RNA. Results The fine needle aspiration smears showed rare, inconclusive stromal pieces. The core biopsy samples displayed spindle cell lesion with smooth-muscle features. There was mild cytological atypia without necrosis or mitotic activity. Immunohisto-chemical stains showed spindle cells were positive for SMA (smooth muscle actin), desmin, and vimentin. S-100 and MNF-116 (cytokeratin stain) were negative. In situ hybridisation for EBER showed nuclear positivity. Conclusions: EBV associated smooth muscle tumours can present as multiple bilateral lung nodules mimicking metastatic tumour. Histologically, they show spindle cell lesion with bland cytological features and low mitotic activity. Supportive ancillary findings by immunohistochemistry and in situ hybridization are as follows: (1) positive for SMA, desmin and vimentin, (2) negative for S-100 and epithelial marker MNF-116, and (3) positive for EBER.