Diffuse large B-cell lymphoma that develops in the setting of long-standing chronic inflammation is typically associated with Epstein-Barr virus, and usually presents as tumor mass involving body cavities, as in pyothorax-associated lymphoma. It is listed as a distinct entity in the latest World Health Organization lymphoma classification. We report four cases that were incidentally discovered on histologic examination, one each in a splenic false cyst, a long-standing hydrocele, an atrial myxoma, and metallic-implant wear debris. Microscopic foci of atypical (neoplastic) large lymphoid cells were found within the contents of the cysts or curettage material, or within the stroma of the atrial myxoma. Despite the diverse clinical scenarios, all cases showed a homogeneous phenotype: positivity for B-lineage markers (CD20+, CD79a+, PAX5+), non-germinal center immunophenotype (CD10-, BCL6-/+, MUM-1+), and positivity for Epstein-Barr virus with type III latency (LMP1+, EBNA2+). The last feature supports the hypothesis that the lymphoma has arisen in a setting of 'local immunodeficiency' as a result of long-standing chronic inflammation in an enclosed space, a characteristic pathogenetic mechanism of diffuse large B-cell lymphoma associated with chronic inflammation. These cases therefore expand the spectrum of this entity to include new clinical scenarios for the development of this lymphoma type.