PREVALENCE OF MYD88 L265P MUTATION IN HISTOLOGICALLY PROVEN, DIFFUSE LARGE B-CELL VITREORETINAL LYMPHOMA HARISH RAJA, MD,* DIVA R. SALOMÃO, MD,*† DAVID S. VISWANATHA, MD,‡ JOSE S. PULIDO, MD, MS, MPH, MBA* Purpose: Myeloid differentiation primary response gene 88 (MYD88) is a universal adaptor protein in the innate immune system. When associated with a proline for leucine substitution mutation at position 265 (L265P), the protein becomes constitutively activated, amplifying the intracellular pro-inflammatory signal. Recently, we reported two cases of vitreoretinal lymphoma (VRL) that were positive for the mutation. The purpose of this study was to determine prevalence of the MYD88 L265P mutation in a larger series of VRL. Methods: Retrospective chart review of 25 patients with histologically confirmed VRL evaluated at Mayo Clinic, Rochester, between January 2000 and March 2015. Paraffin- embedded blocks from the vitreous were submitted for polymerase chain reaction testing of the L265P mutation. Results: The mutation was positive in 82.4% of all VRL cases and 86.7% of primary VRL cases. The minimum necessary DNA concentration needed for the polymerase chain reaction assay was 4.93 ng/mL. Conclusion: MYD88 gene analysis is a helpful ancillary tool for diagnosing VRL. It often requires fewer cells than flow cytometry or cytology and may be especially useful in early cases where a sufficient number of cells may not be available. RETINA 36:624–628, 2016 T he myeloid differentiation primary response gene 88 (MYD88) encodes a phylogenetically well- preserved protein in the innate immune system. 1 The MYD88 protein is a universal adapter protein used by tolllike receptors, a type of pattern recognition receptor, responsible to amplify downstream pro- inflammatory pathways including NF-kB. A specific amino acid mutation in the MYD88 gene at position 265, where proline is substituted for leucine, has been described in a large (over 90%) proportion of patients with Waldenström’s macroglobulinemia. 1 The presence of this mutation results in constitutive activa- tion of B cells 2 and seems to be the basis of Walden- ström’s macroglobulinemia. 3 The same mutation was described in 10% of patients with systemic diffuse large B-cell lymphoma, a finding which was associated with poorer outcomes. 4 With variable prevalence, it has also been reported in other lymphomas, including 100% of lymphoplasmacytic lymphoma, 5 greater than 80% of testicular lymphoma, 6 ,10% of small B-cell lym- phoma, 5 and 15% of splenic marginal zone lymphoma. 7 More recently, our group has reported two cases of histologically proven, diffuse large B-cell primary vit- reoretinal lymphoma (VRL) with the MYD88 L265P mutation. 8 In these cases, the mutation was detected using an ARMS polymerase chain reaction (PCR)- based assay. To our knowledge, the presence of the MYD88 L265P mutation has not been reported in non- neoplastic, ocular inflammatory conditions. The frequency of the MYD88 L265P mutation in VRL has not yet been well established. Bonzheim et al 9 recently reported close to 70%. In this article, we From the Departments of *Ophthalmology, †Anatomic Pathol- ogy, and ‡Hematopathology, Mayo Clinic, Rochester, Minnesota. Supported by Research to Prevent Blindness, New York, NY, and also by a grant from VRS Foundation, Minneapolis, MN. Paper presented at Maculart, Paris, France, June 28, 2015. None of the authors have any financial/conflicting interests to disclose. Reprint requests: Jose S. Pulido, MD, MS, MPH, MBA, Department of Ophthalmology and Department of Molecular Medicine, Mayo Clinic, 200 First Street, SW, Rochester, MN 55905; e-mail: pulido.jose@mayo.edu 624