What are stromal neoplasms?

➢ FA and PT share driver mutations in the same genes and appear to be part of a spectrum of related neoplasms. ➢ Tumors derived from intralobular stroma are comprised of both stromal cells and epithelial cells :“biphasic” ➢ The neoplastic proliferation of specialized lobular fibroblasts also stimulates reactive proliferation of lobular epithelial cells. ➢ As the intralobular fibroblasts proliferate, they push and distort the epithelial cells so that they form elongated slitlike structures rather than round acini. ➢ in phyllodes tumors the stromal cells tend to outgrow the epithelial cells, resulting in bulbous nodules of proliferating stromal cells that are covered by epithelium ➢ Lesions of interlobular stroma are monophasic (only comprised of mesenchymal cells) and include benign soft tissue tumors found elsewhere in the body, such as hemangiomas and lipomas ➢ The only malignancy derived from interlobular stromal cells of note is angiosarcoma which may arise in the breast after local radiotherapy.