Sclerosing lobular hyperplasia--cytological similarity to fibroadenoma.

Mammary sclerosing lobular hyperplasia (SLH) is a rare, benign, fibroproliferative tumour-like lesion of adolescent and young women often of African-American heritage. Fine-needle aspiration cytology of mammary SLH shows characteristic features that include an absence of stromal fragments. We report a 45-year-old woman who presented with a gradually enlarging, painless, mobile 4-cm tumour in her left breast. Fine-needle aspiration cytology performed preoperatively was characterized by some fibroadenoma-like features including the presence of stromal fragments and bare nuclei. However branched tubular fragments, typical of fibroadenoma, were not seen. A diagnosis of benign epithelial lesion of the breast was offered, and the possibility of a fibroadenoma was suggested. Excision biopsy histology revealed SLH. The key cytological features of mammary SLH are bland ductal epithelial cell clusters, few scattered fragments of stroma, relatively clean background with a fair number of bare nuclei. However these are not diagnostic as they overlap with those of fibroadenoma and distinction between the two benign entities is of no clinical significance. The definitive diagnosis of SLH requires histopathological evaluation.