Malignant myoepithelioma arising in adenomyoepithelioma of the breast and coincident multiple gastrointestinal stromal tumours in a patient with neurofibromatosis type 1.

A 41-year-old female patient with neurofibromatosis type 1 (NF-1) presented with a breast lump and anaemia related to gastrointestinal bleeding. She was found to have malignant myoepithelioma of the breast and simultaneously multiple gastrointestinal stromal tumours (GISTs) of the small bowel. Molecular studies showed a silent germline mutation in exon 9 of the KIT gene of both tumours. The common gene mutations characteristic of sporadic GISTs were not identified in these tumours, consistent with the literature, suggesting that gene mutations in GISTs are either absent or late events in patients with NF-1.