An individual with a twin who has developed leukemia or non-Hodgkin lymphoma (NHL) has an increased risk of developing the same disease, particularly with monozygotic twins. The few reported pairs of twins who developed NHL had similar primary sites and pathological subtypes. Here, we present the first reported cases of primary conjunctival NHL in both female monozygotic twins. Twin 1 was diagnosed with an extranodal marginal zone lymphoma (EMZL; Ann Arbor stage IE) in the right conjunctiva at 25 years old and a subsequent tumor in the left conjunctiva at 39 years, and was also histopathologically diagnosed as EMZL. No infiltration of other organs was detected and both lesions were surgically excised. At the age of 40 years, Twin 2 was diagnosed with an EMZL (Ann Arbor stage IE) in the right conjunctiva without infiltration of other organs and was treated with external beam radiation therapy rather than surgery. Complete remission was achieved in both twins; neither developed conjunctival recurrences. This study highlights the importance of examining the other, apparently healthy twin when one twin develops conjunctival lymphoma.
Keywords: EMZL; conjunctival lymphoma; monozygotic twins.