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Histopathology of cutaneous reaction to granulocyte colony‐stimulating factor: another pseudomalignancy

Granulocyte colony‐stimulating factor (G‐CSF) is a hematopoietic growth factor (HGF) with many applications in cancer therapy. The most important applications are reduction in the incidence of febrile neutropenia, acceleration of neutrophil recovery after chemotherapy or bone marrow transplantation, and mobilization of progenitor cells. Many cutaneous adverse reactions associated with HGF have been reported in recent years, including injection site reactions, pyoderma gangrenosum, Sweet's syndrome, cutaneous leucocytoclastic vasculitis, and widespread folliculitis. The presence of large histiocytes on the dermis between collagen bundles has been proposed as a characteristic histopathologic finding in cutaneous eruptions secondary to granulocyte colony‐stimulanting factor and granulocyte‐macrophage colony‐stimulating factor. We report on a patient with a high‐risk ductal infiltrating carcinoma of the breast who received high‐dose chemotherapy (HDC) with peripheral blood progenitor cell (PBPC) rescue. The patient received G‐CSF after PBPC for a faster granulocyte recovery. She developed a cutaneous eruption located on back, buttocks, axillae, groin and sites where electrocardiography electrodes had been placed. From the histopathological point of view, the eruption was characterized by the presence of numerous large, atypical histiocytes in the dermis with several mitotic figures, mimicking involvement of the dermis by a malignant process.