A 62-year-old man developed a large red nodule on his right lower jaw 6 months before visiting our clinic, followed by multiple nodules and erythema soccurring on his head and trunk. He visited the department of plastic surgery of Hamanomachi Hospital and had the large nodule removed surgically. A histopathological examination revealed dense mononuclear cell infiltration in the dermis without apparent nuclear atypia or conspicuous mitosis. Infiltrating cells were a mixture of numerous B and T cells as assessed immunohistochemically. Sections from the other nodules and the erythema were histologically very similar and no gene expression of immunoglobulin heavy chain or T-cell receptor β and γ chains was detected in these additional specimens. Cervical to inguinal computed tomography scanning and blood examination showed no evidences of malignant lymphoma. The diagnosis of pseudolymphoma was made from the above findings. The nodules and erythema disappeared after local injection of triamcinolone acetonide, but some eruptions flared and others newly appeared, necessitating monthly treatments. Careful follow-up is needed since cases of malignant lymphoma occurring from pre-existing pseudolymphoma have been reported.
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