Atypical Molluscum Contagiosum Accompanied by CD30-Positive Lymphoid Infiltrates

Abstract

Abstract:  Atypical presentations of molluscum contagiosum require histophathologic examination and may show pleomorphic lymphocytic infiltrates of a reactive nature, mimicking cutaneous lymphoproliferative diseases. Serial sections of specimens or polymerase chain reactions to show T-cell receptor clonality may be helpful for differential diagnosis. We report a case of atypical molluscum contagiosum accompanied by atypical lymphocytic infiltration showing CD30 positivity.

A 5-year-old boy presented with a red nodule on the posterior neck (Fig. 1). The lesion had appeared 1 month before and had recently increased in size. He had no symptoms and denied a history of trauma or insect bite. Physical examination showed no evidence of lymphadenopathy or organomegaly. He had a history of idiopathic thrombopenic purpura and had been treated with corticosteroid and intravenous immunoglobulin 2 years earlier. At presentation, his platelet count was within normal limits, and other laboratory findings were normal.

Figure 1.  A 1-cm-sized red nodule on the posterior neck of a 5-year-old boy.

Histopathologic examination revealed a florid cellular infiltrate with eosinophilic inclusion bodies (Fig. 2A). The cellular infiltrates were composed predominantly of pleomorphic lymphocytes. There were many eosinophils and some red blood cells (Fig. 2B). Immunohistochemistry showed that the large lymphocyte cells were positive for CD30 (Fig. 2C), with approximately 60% of the lymphoid cells expressing the proliferation marker Ki-67. Serial sections of the specimen showed more prominent inclusion bodies, confirming the diagnosis of molluscum contagiosum (MC). Thus, he was diagnosed with MC containing CD30-positive lymphoid infiltrates and did not have any further treatment.

Figure 2.  (A, B) A florid cellular infiltrate surrounding eosinophilic inclusion bodies [hematoxylin and eosin, original magnification (A) ×40, (B) ×200]. (C) Immunohistochemistry showed that the infiltrating cells were positive for CD30 (× 40).

Discussion

MC is a common disease during childhood, usually presenting as smooth-surfaced papules, although atypical presentations such as large and tender nodules require biopsies to exclude neoplastic processes. Biopsies of these lesions show pleomorphic lymphocytic infiltrates of a reactive nature, which can mimic cutaneous lymphoproliferative diseases, including lymphomatoid papulosis.

In general, MC shows a paucity of infiltrating T cells (1). The presence of a lipid cover around the molluscum bodies, as well as a thin membrane surrounding the virions (2), accounts for the typically weak immune response after MC infections, but trauma to or manipulation of these covers exposes the viral antigens to the immune system, amplifying the inflammatory response and resulting in a dense cellular infiltrate that may include atypical lymphocytes (1,3). MC has therefore been considered to be a cause of pseudolymphomatous infiltration, and CD30-positive lymphoid infiltrates have been associated with other viral infections, including warts (4). A review of 28 patients with benign skin lesions containing atypical lymphoid infiltrates found that viruses were most commonly responsible for the presence of CD30-positive cells in cutaneous inflammatory infiltrates (5). Thus, a viral infection should be suspected when evaluating histopathologic specimens with large CD30-positive cells, although expression of CD30 has been considered a hallmark of primary cutaneous T-cell lymphomas, such as lymphomatoid papulosis. In our patient, the presence of typical viral inclusion bodies of MC resulted in a diagnosis of MC rather than CD30-positive primary cutaneous lymphoma after examination of serial sections of the specimen.

We report a case of CD30-positive lymphoid infiltrate associated with MC, which was a reactive process to a ruptured cystic lesion of MC. CD30-positive primary cutaneous T-cell lymphoma should be diagnosed only after accurate clinicopathologic correlation and when a reactive condition such as viral infection has been excluded. In such cases, serial sectioning of specimens and careful examination would be important before conducting other costly examinations such as immunohistochemical stains.