Hypopigmented macules secondary to imatinib for the treatment of chronic myeloid leukemia: a histopathologic and immunohistochemical study

Background A few series addressing the cutaneous side effects related to imatinib in the skin have been published, but only one described scarce histopathologic information in seven patients. Objective To characterize these lesions and compare the number of melanocytes between hypopigmented lesions and normal appearing skin. Methods We retrieved clinical data of the patients and performed 24 skin biopsies (13 from hypopigmented skin and 11 from normal-appearing skin) within a cohort of 41 patients with chronic myeloid leukemia treated with imatinib. We classified the biopsies into three patterns. Results About 45% of patients presented with periocular hypopigmentation. Perifollicular fibrosis was observed in hypopigmented skin biopsies (76.9%) and in normal-appearing skin (45.5%). Epidermal melanin, as determined with Masson-Fontana staining, and melanocyte number, as evaluated with MiTF, Melan A and c-kit immunostains, were lower in hypopigmented skin. Conclusions Histopathologic study of hypopigmented macules demonstrates the presence of melanin with a statistically significant decrease in the number of melanocytes. Therefore, these findings differ from vitiligo, as melanocytes are present. Three histopathological patterns may be found, namely (a) perifollicular fibrosis, (b) lichen planopilaris-like and (c) apparently normal skin. One of the most striking histopathologic finding consisted of the presence of perifollicular fibrosis in both hypopigmented lesions and apparently normal skin.