Adenosis tumour of the breast-a clinicopathological investigation of 27 cases

Twenty‐seven cases of palpable and/or tumour‐forming adenosis in the female breast, called adenosis tumour, have been investigated. It is a rare lesion, which most often presents as a breast mass that clinically and histologically is sometimes misinterpreted as carcinoma. The majority of patients were under the age of 45 years. Grossly, most tumours were firm or elastic and showed a grey or greyish‐white cut surface. Furthermore, seven (26%) were granular and nine (34%) were microcystic, whereas none showed chalky streaks. Microscopically, 20 cases were poorly circumscribed and seven cases were well circumscribed. In contradistinction to the often uniform growth pattern of tubular carcinoma, the adenosis tumours characteristically showed adenosis arranged in a mixture of eight different growth patterns. The most frequent and also most extensive growth pattern was classical sclerosing adenosis and the least frequent was tubular adenosis. Another conspicuous feature in adenosis tumours was patchy growth in contrast to the stellate configuration of tubular carcinoma which is the most likely differential diagnosis. Other findings separating adenosis tumours from carcinomas were microcysts (93%), apocrine metaplasia (63%), luminal histiocytes (52%) and pseudopapillomas, called glomeruloid structures (48%). Epithelial changes that could cause anxiety about malignancy were frequently found and comprised epithelial hyperplasia (44%), epithelial atypia (26%) and fat or nerve infiltration (30%). Three patients were subjected to unnecessary mastectomy because of incorrectly diagnosed adenosis tumours. Adenosis tumours and non‐infiltrating carcinoma were found together in five cases, but their association is probably over represented due to selection. None of 18 pure adenosis tumours solely treated by excision had recurred at follow‐up 1–9 years later (mean 3.75 years).