Tumors that express keratin include carcinomas, thymomas, sarcomas and trophoblastic neoplasms. These tumors characteristically display hypovascular stroma compared to malignant neoplasms. Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. Most mature lymphoid neoplasms comprise the non-Hodgkin lymphomas. The most common salivary gland neoplasms in children are hemangiomas, lymphatic malformations, and pleomorphic adenomas. The incidence of mammary desmoid tumours is less than 0.2% of primary breast neoplasms. Cells in pre-malignant and malignant neoplasms (tumors) evolve by natural selection. The majority of deaths were caused by neoplasms, mainly mammary tumors. Myeloid neoplasms always concern bone marrow cell lineage and are related to hematopoietic cells. Such mutations and epigenetic alterations can give rise to cancer (see malignant neoplasms). The cancers included cancer of the brain, lung, bowel, breast, and bladder, and other neoplasms. It is also overexpressed in some cell lines originating from various malignant neoplasms. The pre-procedure mammograms were negative for malignant neoplasms. In pathology, grading is a measure of the cell appearance in tumors and other neoplasms. Sertoli-Leydig cell tumour is part of the sex cord-stromal tumour group of ovarian neoplasms.