Immunocytoma of the skin simulating lymphadenosis benigna cutis.

We report a case of primary cutaneous lymphoma, of the lymphoplasmacytoid type (immunocytoma), in which a small neoplastic component was obscured by a dominating reaction exhibiting characteristic features of lymphadenosis benigna cutis. This abnormal cell population was identified because of the unusual cytomorphology of the tumor cells, which showed deeply indented nuclei in combination with a distinctly plasmacytic cytoplasm. Monoclonality was revealed by the cytoplasmic positively of the tumor cells for lambda chains only. This case strongly suggests that in at least a number of cases of lymphadenosis benigna cutis, a low-grade malignant lymphoma may be present.