Ocular adnexal lymphoma: Subtype-specific clinical and genetic features

Ocular adnexal lymphoma is a relatively rare disease but is one of the most common malignancies in the ocular adnexa, and its incidence is steadily increasing. Ocular adnexal lymphoma consists mainly of four histopathological subtypes of non-Hodgkin B-cell lymphoma: extranodal marginal zone lymphoma (EMZL), follicular lymphoma (FL), mantle cell lymphoma (MCL) and large B-cell lymphoma (LBCL). The clinical characteristics associated with each of the subtypes are not well known due to the sparsity of cases. Furthermore, a number of molecular and phenotypic features have been identified as recurrent and prognosticating in LBCL but are not yet well documented for the ocular adnexal region: concurrent MYC and BCL2 and/or BCL6 rearrangements, MYC/BCL2 double-expressor phenotype (in diffuse large B-cell lymphomas), and MYD88 and CD79B mutations. Therefore, the present PhD study aimed to investigate the clinical features of (1) conjunctival lymphoma by subtype and (2) ocular adnexal MCL in an international multicentre cohort of 307 patients and (3) the clinical and genetic features of ocular adnexal LBCL in 34 Danish patients. This was performed by collecting clinical data on the patients and tissue samples of the LBCLs. The tissue samples were analysed immunohistochemically for phenotype, by allele-specific PCR and Sanger sequencing for the presence of the mutations, and by fluorescence in situ hybridisation for the rearrangements. Statistical analyses were performed to detect correlations with clinical features and survival. The analyses revealed that conjunctival EMZL and FL typically presented in individuals in their 60s as localised unilateral tumour masses and had favourable prognoses (5-year disease-specific survival: 82%-97%). LBCL and MCL were found in all the ocular adnexal structures, with the orbit being the most common location (82% and 58%, respectively). These lymphomas typically presented in patients in their 70s, with MCL having a male predominance. MCLs commonly presented with bilateral lesions and systemic involvement, while LBCLs were unilateral localised tumours. Both subtypes had poor prognoses, with 49%-62% of patients having succumbed to the disease within 5 years. Ocular adnexal LBCLs had presence of concurrent MYC and BCL2 and/or BCL6 rearrangements in 16% of cases, MYC/BCL2 double-expressor phenotype in 44% of diffuse large B-cell lymphomas, and MYD88 ± CD79B mutations in 29% of cases. MYC/BCL2 double-expressor phenotype and MYD88 mutations were associated with adverse prognoses. All in all, the results indicate that the histopathological subtype of ocular adnexal lymphoma is a major outcome predictor. Furthermore, the results underline the importance of analysing the expression of MYC and BCL2 by immunohistochemistry in diffuse large B-cell lymphoma patients and advocate for incorporating the analysis of MYD88 mutations in the routine diagnostic workup of ocular adnexal LBCL. SUMMARY IN DANISH: Lymfomer i øjenregionen (orbita, conjunctiva, øjenlåg, tårekirtel og tåresaek) er relativt sjaeldne tumorer, men er blandt de hyppigste cancerformer i denne region og forekomsten er hastigt stigende. Lymfomer i øjenregionen består hovedsageligt af 4 undertyper af non-Hodgkin B-celle lymfom: ekstranodalt marginal zone lymfom, follikulaert lymfom, storcellet B-celle lymfom og mantle celle lymfom. Grundet sygdommens sjaeldenhed er kliniske karakteristika ved de forskellige lymfomundertyper kun sparsomt undersøgt. Endvidere er der blevet identificeret en raekke prognostisk vigtige molekylaere og faenotypiske kendetegn ved storcellede B-celle lymfomer, som endnu ikke er velundersøgt i øjenregionen. Det drejer sig om samtidig rearrangement i MYC og BCL2 og/eller BCL6, samtidig overekspression af MYC og BCL2 samt MYD88 og CD79B mutationer. Dette ph.d.-studie havde derfor til formål at undersøge de kliniske kendetegn ved (1) mantle celle lymfomer i øjenregionen og (2) de forskellige undertyper af conjunktivale lymfomer i en international kohorte med 307 patienter samt (4) de kliniske, molekylaere og faenotypiske kendetegn ved storcellet B-celle lymfom i 34 danske patienter. Vaevsmaterialet med storcellede B-celle lymfomer blev undersøgt ved hjaelp af immunhistokemi for faenotypen, ved hjaelp af allel-specifik PCR og Sanger sekventering for mutationerne og ved hjaelp af fluorescens in situ-hybridisering for rearrangementerne. Der blev udført statistiske analyser med henblik på at finde eventuelle sammenhaenge med kliniske karakteristika og overlevelse. Analyserne viste, at conjunctivalt ekstranodalt marginal zone lymfom og follikulaert lymfom typisk forekom blandt patienter i 60erne som ensidige tumorer uden spredning og var forbundet med en god prognose (5-års sygdomsspecifik overlevelse på 82-97%). Storcellet B-celle lymfom og mantle celle lymfom blev fundet i samtlige strukturer i øjenregionen med orbita som den hyppigste lokalisation (hhv. 82% og 58%). Disse lymfomundertyper forekom primaert hos patienter i 70erne med overvaegt af maend blandt mantle celle lymfomerne. Mantle celle lymfomerne praesenterede sig typisk som dobbeltsidige laesioner i øjenregionen med systemisk involvering, mens storcellede B-celle lymfomer var ensidige tumorer uden spredning. Begge undertyper havde en dårlig prognose, hvor cirka halvdelen af patienterne døde af sygdommen indenfor 5 år. Genetisk var storcellede B-celle lymfomer i øjenregionen karakteriseret ved betydelig praevalens af MYD88 mutationer (29%), som var forbundet med en dårlig prognose. Rearrangementer i MYC og BCL2 og/eller BCL6 forekom i 16% af tilfaeldene. Derudover havde 44% af diffuse storcellede B-celle lymfomer samtidig overekspression af MYC og BCL2, som var associeret med en dårlig prognose for patienterne. Alt i alt viser resultaterne, at den histologiske undertype er en vigtig prognostisk faktor for lymfomer i øjenregionen. Derudover fremhaever resultaterne vigtigheden af undersøgelsen af MYC/BCL2 faenotypen og implementeringen af MYD88 mutationsundersøgelsen i rutinediagnostikken af storcellede B-celle lymfomer i øjenregionen.