Cutaneous pseudolymphomas: classification and differential diagnosis

Cutaneous pseudolymphomas are benign hyperplastic lymphoproliferative reactions that simulate cutaneous malignant lymphomas clinically and/or histologically. The differentiation between cutaneous pseudolymphomas and primary cutaneous lymphomas is often very difficult, but is important because it has therapeutic consequences. The term pseudolymphoma does not refer to a specific disease, but to a heterogeneous group of pseudo-B-cell lymphomas and pseudo-T-cell lymphomas. In this article clinical and histological features of this group of disorders will be discussed and the differential diagnostic criteria, that have been used in the past decades to differentiate between cutaneous lymphomas and pseudolymphomas will be critically evaluated.