Diagnostic pitfall in a case of ductal carcinoma-in situ with microinvasion.

We report a case of microinvasive carcinoma of the breast cytologically diagnosed as ductal carcinoma - in situ in an 80-year-old lady with a breast lump. Extensive sampling of mastectomy specimen showed ductal carcinoma in situ (DCIS). Many ducts showed stromal reaction - periductal sclerosis and lymphocytic infiltration-features suggestive of microinvasion. However, no definite invasion was noted histologically. Immunohistochemical study highlighted the microinvasive foci.