Abstract

The morphologic study of noninfiltrating and infiltrating duct carcinoma of the breast disclosed profound alterations along the parenchymal-stromal junction. But fate of myoepithelial cell, changes of basement membrane and the relationship of fibroblast to myofibroblast remain uncertain. To study the morphologic changes of myoepithelial cell, basement membane and stromal fibroblast, a series of 32 not otherwise specified (NOS) type of infiltrating duct carcinoma of the breast with regional lymph node metastases was examined light microscopically after S-100 protein immunoperoxidase staining by biotinavidin system (BAS) and ultrastructurally. The results were as follows. 1) In 18 out of 32 cases, S-100 protein positive myoepithelial cells were observed individually in the parenchyma at the periphery of some carcinomatous duct-like structures or cancer cell nests. The cells were noted in 7 cases of metastatic regional lymph nodes. In 5 cases contained with 2 cases of infiltrating duct carcinoma with focal sarcomatous metaplasia, S-100 protein positive cells were seen in fibroblast-like spindle cells in stroma adjacent to cancer nests. 2) Ultrastructural features of myoepithelial cells showed significant loss of fine microfilament and hemides-mosomes and relative imcrease of coarse large filaments. Morphologic transformation of myoepithelial cells to neoplastic epithelial cells or stromal fibroblast-like spindle cells were suggested in 3 NOR type and 2 metaplastic type carcinomas. 3) The ultrastructural changes of basement membrane disclosed some variations from case to case and even within a single tumor if large number of blocks were studied. Focal destruction, splitting, segmentation and extensive loss of basement membrane arround cancer nests were noted. On the other hand, basement membrane material surrounded cancer nests or individual cancer cells irregularly. 4) Most stromal fibroblasts in infiltrating duct carcinoma had abundant rough endoplasmic reticulum with enlarged plump cytoplasm. Some of them were transformed to myofibroblasts which had perinuclear rough endoplasmic reticulum and peripheral microfilaments with dense bodies in their cytoplasm.

• Keywords: Breast cancer;Myoepithelial cell;Basement membrane;Fibroblast;Myofibroblast