KIT gene mutations in Ewing sarcomas are rare; however, they are much more frequent in other neoplasms, namely mastocytosis. We describe a case of an adult male with a one-year duration of recurrent episodes of pain, swelling, and redness on the proximal phalanx of the third finger of his right hand. A core biopsy suggested a possible mastocytosis. After four years of recurrent episodes and worsening symptoms, ...