Mucosal pigmentation caused by imatinib: report of three cases

Imatinib mesylate (STI-571, Gleevec(®)), a tyrosine kinase inhibitor, is a first-line medication for treating chronic myeloid leukemia (CML). Clinical studies revealed very good hematological responses without significant side effects. However, imatinib may lead to mucosal pigmentation. Three patients, two males aged 64 and 53 and one female aged 29 presented with a painless, diffuse, grey-blue pigmentation of the mucosa of the hard palate. Both male patients had a history of CML and had been on imatinib for 4 and 10 years, respectively. The female patient had been on imatinib for 4 years for pelvic fibromatosis. Histopathologically, deposition of fine, dark-brown, spherical granules was noted within the connective tissue. There was no inflammation or hemorrhage, and no melanosis or melanocytic hyperplasia in the epithelium. The granules stained positively for both Fontana-Masson and Prussian blue stains. Imatinib-induced pigmentation is similar to that caused by other medications such as minocycline and anti-malarial medications, namely the deposition of a drug metabolite containing melanin and iron.