ABSTRACT
<p><b>OBJECTIVE</b>To study the morphologic classification of mammary ductal hyperplasia, and its criteria and the significance in distinguishing atypical hyperplasia from carcinoma-in-situ.</p><p><b>METHODS</b>The clinicopathologic features of 300 cases of hyperplasia of breast were reviewed. Whole-organ H&E sections were also available in 86 cases of breast carcinoma. The occurrence of atypical hyperplasia in adjacent breast tissue was assessed.</p><p><b>RESULTS</b>Fibroadenomatoid changes were typically observed in the 21-30 age groups and atypical hyperplasia occurred more frequently in 40-60 age groups. Amongst the hyperplastic cases, cystic diseases of the breast were noted in only 6%. In contrast, fibroadenomatoid changes were more common (25.4%). Atypical ductal hyperplasia occurred in adjacent breast tissue of 65.1% of the carcinoma cases. The incidence was higher (74.9%) if the main lesion was ductal carcinoma-in-situ.</p><p><b>CONCLUSIONS</b>There is a close association between atypical hyperplasia and breast carcinoma. It is prudent to distinguish between usual and atypical hyperplasia. Morphologic differentiation between atypical ductal hyperplasia and ductal carcinoma-in-situ may sometimes be difficult.</p>