CD10-positive myoepithelial cells are usually prominent around in situ lobular neoplasia of the breast and much less prominent or absent in DCIS.

Aims: To study the relationship between the neoplastic cells of in situ lobular neoplasia (ILN) and ductal carcinoma in situ (DCIS) and the surrounding CD10-positive myoepithelial cells.

Materials And Methods: Twenty consecutive cases of ILN and 51 of DCIS were stained for CD10 using the immunoperoxidase technique. The presence of CD10-positive cells was assessed semiquantitatively on a scale of 0-3 where 0 indicates their absence and 3 indicates the presence of multiple layers, which can be focal.