Cutaneous granulocytic sarcoma and Koebner phenomenon in a context of myelodysplastic syndrome

CGS: cutaneous granulocytic sarcoma GS: granulocytic sarcoma IHC: immunohistochemistry KP: Koebner phenomenon MDS: myelodysplastic syndrome MPO: myeloperoxidase PG: pyoderma gangrenosum TGF-b1: transforming growth factor-beta 1 TGF-b1R: transforming growth factor-beta 1 receptor INTRODUCTION Granulocytic sarcoma (GS) is also known as myeloid sarcoma or chloroma because of its green hue caused bymyeloperoxidase (MPO). This disease involves the localization of myeloblasts or immature myeloid cells to an extramedullary site. GS has been described at numerous anatomic sites, but cutaneous GS (CGS) is uncommon. Although CGS is rare, it is clearly associated with myeloid disorders, such as acute myeloid leukemia, myeloproliferative neoplasms, and myelodysplastic syndromes (MDSs). CGS may herald acute transformation, and it is associated with a poor prognosis. However, the mechanism underlying the specific migration of myeloblasts to the skin remains uncertain. In 2008, Kawakami et al presumed that transforming growth factorebeta 1 (TGF-b1) released by hematopoietic cells within the cutaneous extramedullary hematopoiesis could play a role in the onset of such skin lesions. We report a case of a patient with MDS presenting with 2 CGSs that developed consecutively at traumatized skin sites, suggestive of the Koebner phenomenon (KP). Immunohistochemical (IHC) analysis confirmed the expression of TGF-b1 on myeloblasts and fibroblasts that had infiltrated the CGSs but also showed the expression of its specific receptor (TGF-b1R), suggesting a role for this cytokine in cutaneous tropism and the pathogenesis of the KP.