Leukemic cells within skin lesions of psoriasis in a patient with acute myelogenous leukemia

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Abstract
We report on an 81‐year‐old man with acute myelo‐monocytic leukemia (FAB M4) and a long‐standing history of psoriasis. Biopsy of psoriatic plaques revealed the coexistence of characteristic histopathologic aspects of psoriasis together with an infiltrate of blasts with features of myelo‐monocytes, suggestive of a specific leukemic infiltrate within plaques of psoriasis. Immunohistologic stainings showed positivity of blasts for LN2 (CD74), MT1 (CD43), and lysozyme, consistent with a myeloid lineage of these cells. To the best of our knowledge, this is the first report on the association of psoriasis with myelogenous leukemia. The presence of leukemic cells within psoriatic skin plaques may be explained by non‐specific recruitment of recirculating malignant cells to the skin. Alternatively, as psoriasis is an inflammatory disease involving granulocytes among other cell types, it may be hypothesized that leukemic cells retain to some extent their capability to respond to physiologic stimuli and enter the skin in response to specific chemotactic factors.