Hyperplasia is a term used to describe rapid and unexpected new cell growth in various tissues, but in the context of breast cancer screening it usually refers to the lining of the breast ducts. 'Florid' hyperplasia is a term which describes the degree or amount of hyperplasia, on an informal continuum from mild, to moderate, to florid. Hyperplasia is usually described as 'typical' or 'atypical'. Only the 'atypical' variety is of concern for possible breast cancer, and even this assertion is highly debatable.
Normally, the linings of the breast ducts contain no more than two layers of unique cuboidal cells, along with basal 'contractile' myoepithelial cells. These cells form a distinct luminal border (a distintive wall around the empty space of the breast duct). If there is a noted increase in the number of cells that constitute this ductal lining (a 'proliferation'), it is termed epithelial hyperplasia. Whether or not this 'simple' or 'typical' hyperplasia starts to be considered as 'atypical' will depend on the number of cells, the 'nuclear' appearance of these cells, and the extent to which the lining itself becomes distorted. The pathologist will also consider the 'admixture' of different types of cells (the balance of epithelial, myoepthelial, and metaplastic apocrine cells that may be present).
With florid hyperplasia, the lumen (empty space of the duct) is distended, possibly obliterated due to large numbers of neoplastic cells. Certainly this is somewhat or an 'atypical' development, but usually the use of that term is restricted to very unusual looking cells, or cell growth in tissues where they really do not belong.
Any kind of cell proliferation per se is considered a very mild increase for breast cancer development as compared to an average woman without the condition. But unless there are 'atypical' features to the new developments, florid hyperplasia cannot be considered a direct increased risk factor for breast cancer.
'Traditional' wisdom tends to suggest that there is a cumulative increased risk factor as one progresses from normal ductal epithelial cells, to mild hyperplasia, to florid hyperplasia., then to atypical ductal hyperplasia, and finally to ductal carcinoma in situ. However, there really is no direct evidence that any degree of hyperplasia and even atypical hyperplasia are precursors to DCIS or to invasive breast cancer. The only 'ductal proliferation' which has been consistenly linked to invasive breast cancer is DCIS.
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