The study of tumors of the breast has given rise to many controversial points both as to their origin and as to the predisposing factors in their development. This has been especially true in the case of epithelial tumors. On the other hand, those arising from connective tissue and falling into the category of sarcomas have been neglected because of their rarity and also because of the unsettled state regarding their classification. An unusual opportunity is afforded the investigator attempting to elucidate the question of the relationship between the epithelial and the connective tissue elements in neoplasms of the breast by studying the group classified either as adenomas or as adenofibromas. In this group of tumors of the breast, actively proliferating periductal and periacinal fibrous tissue, which differs from the connective tissue elsewhere in the breast, as well as hyperplastic glandular structures, is present.
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