Expect the unexpected

Primary lymphomas of the lacrimal sac (PLLS) are rare, but are a genuine cause of secondary acquired nasolacrimal duct obstruction.1 The aim of the article on PLLS by Sjö et al2 in this issue of the BJO (p 1004) was to define their clinical and histopathological characteristics. Their report on 15 cases of PLLS studied more than seven times the number of cases than the next largest publications defining this subject.

The authors, within the limits of a multinational (seven European nations), multicentre, retrospective, chart based study have achieved an excellent outcome in defining the histopathological features of the 15 cases of PLLS. The authors presumably assembled all the cases of PLLS they had on record, or could recall, from the two European pathology institutes that are named in their article. They were able to retrieve the relevant blocks, and to subject the specimens to a battery of stains with haematoxylin and eosin and an immunohistochemical panel with multiple antibodies. No less than five experienced pathologists examined each section, and in difficult cases a consensus diagnosis was reached. This is a superb approach to a rare clinical problem.

The authors demonstrated convincingly that B cell lymphomas were exclusive in this study. Five each of the 15 (33%) were diffuse large B cell lymphoma (DLBCL) and extranodal marginal zone B cell lymphoma of mucosa associated lymphoid tissue (MALT lymphoma). The authors found three “transitional MALT” lymphomas, and two unclassified B cell lymphomas, the latter so named because of an inadequate volume of tissue. As the authors point out, there have been fewer than 50 cases of PLLS reported in the past 30 …