Diffuse cutaneous pseudolymphoma due to therapy with medicinal leeches.

Report of aCase |Awomanonher50spresentedwitha6-month historyofmultiple, firm, reddish, pruritic andexcoriatedpapulesandnodulesextensivelydistributedontheback (Figure 1). The patient was otherwise healthy, with a medical history of only fibromyalgia, andbothclinical examinationandbloodtest findings were unremarkable. Histologic examination of 2 punch biopsy specimens taken from the nodules on the back showed a prominent dermal nodular lymphoid infiltrate with germinal centers surrounded by a dense infiltrate composed of small round lymphocytes, histiocytes, mature plasma cells, eosinophils, and a smaller percentage of larger centrocyte-like cells (Figure 2). Most of the cells in the infiltrate were positive for the pan-B cell markers CD20 and CD79a. The cells in the germinal centers were also positive for CD10 and BCL6 and negative for BCL2. The small lymphocytes in the infiltrate were positive for CD3. On the basis of the overall histologic findings, a working diagnosis of primary cutaneous B-cell lymphoma of marginal zone was initially considered, but the histologic specimens were subsequently referred for a second opinion to an expert dermatopathologist. The histologic review suggested a possible differential diagnosis of cutaneous pseudolymphoma mimicking a marginal zone lymphoma, further supported by the absence of light-chain restriction by in situ hybridization. Questioning the patient again revealed that 5 or 6 weeks prior to the onset of the skin eruption, she had undergone a course of natural therapy for chronic fibromyalgia that involvedapplyingmedicinal leeches (Hirudomedicinalis).Therefore, a favoreddiagnosisofpseudolymphomasecondary to the application of leeches was made.