Microinvasive lobular carcinoma arising in a benign phyllodes tumour - a short report and brief review of the literature

Lobular carcinoma in situ (LCIS) with microinvasion is a rare entity which is rarely reported in the literature. We describe a case of microinvasive LCIS following excision of a fibroepithelial lesion. The lesion was graded as U3 and M3 on ultrasonography and mammography respectively, and on core needle biopsy was described as a fibroepithelial lesion with 'unusual features'. Microscopic examination revealed a fibroepithelial lesion focally colonised by florid E-cadherin negative LCIS with multiple foci of microinvasive classical lobular carcinoma, which lacked a myoepithelial layer on CK5 and S100 staining.