Cutaneous B-cell pseudolymphoma at the site of vaccination.

Pseudolymphomas are a rare complication of vaccination, presenting with dense lymphoid infiltrates and prominent follicular pattern. We report our observations on 4 patients with vaccination-induced B-cell pseudolymphoma (all females; age range 19 to 60 years; median: 34.5 years). Clinically 3 patients presented with subcutaneous nodules and 1 presented with a large, indurated, erythematous plaque. Histology revealed in all cases dense lymphoid infiltrates in the subcutaneous fat with prominent follicular pattern. The follicles displayed features of reactive germinal centers (normal mantle zone, presence of tingible body macrophages, normal proliferation). Necrotic areas surrounded by palisaded histiocytes were seen in 3 biopsies from 2 patients. A mixed-cell infiltrate with eosinophils and plasma cells was present in all cases. In addition, histiocytes with granular basophilic cytoplasm could be observed around the focal area of necrosis or within the inflammatory infiltrate. Follow-up was available for 3 patients. One patient was alive with persistent disease 6 months after the first observation. Two patients were treated with local radiotherapy and are alive and free of disease after 12 and 72 months, respectively. One of these two patients had a second pseudolymphoma on the contralateral arm after a new injection of vaccine. Cutaneous pseudolymphoma after vaccination should be distinguished histopathologically from low-grade cutaneous B-cell lymphomas (follicle center cell lymphoma, marginal zone lymphoma) and from other B-cell pseudolymphomas with prominent follicular pattern requiring different treatment (eg, Borrelia burgdorferi-induced lymphocytoma cutis).