Fibromata of the female breast are sometimes pure and sometimes in combination with adenomata, sarcomata, myomata and cysts in the form of fibrosarcomata, fibromyomata and fibrocystomata. Fibromata develop mainly from proliferation of the connective tissue surrounding the acini and the small excretory ducts (pericanalicular fibroma). They are most frequent in young persons from seventeen to thirty years of age and are very rare beyond the fortieth year.
Pure fibromata usually form in even, solid nodules of about the size of a walnut or a hen's egg, which, in contradistinction to carcinomata, are freely movable within the breast. In rare cases, especially when combined with cystoma, fibromata attain considerable size. Schimmelbusch classifies cystosarcoma, phylloides (J. Muller), myxoma intracanalicular (Virchow) and serocystic sarcoma (Brodie), all of which tumors may attain an enormous size among the benign fibroadenomata, and thinks they should be distinguished from the true cystic sarcomata