Distribution of calponin and smooth muscle myosin heavy chain in fine-needle aspiration biopsies of the breast

The cell types that may be present in any fine-needle aspiration biopsy (FN AB) of breast include epithelial cells (EC), myoepithelial cells (MEC), bip olar stromal cells (BSC), vascular pericytes/endothelial cells (VPEC), and adipose cells (AC. The recognition of most of these benign cellular element s in aspirates of the breast is relatively straightforward, based an distin ct cytomorphologic criteria. However, there is controversy regarding the re cognition of MEC because BSC are often referred to as MEC by cytopathologis ts. It is important to identify MEC in breast aspirates because their prese nce has been associated with benign epithelial proliferations. In this study we used immunocytochemical methods on archival cytology slide s with antibodies specific for MEG, calponin, and smooth muscle myosin heav y chain (SMMHC), to determine the distribution of MEC in FNAB of the breast and to ascertain the distribution of MEC in in situ and invasive carcinoma s. Fifteen benign FNABS of breast and corresponding tissue biopsies were obtai ned along with 10 malignant FNABS and corresponding excisional breast biops ies from 1989-1993. Calponin and SMMHC antibodies were used on archival alc ohol-fixed Papanicolaou-stained direct smears as well as rite corresponding tissue sections. The distribution and pattern of positive immunostaining w ith both antibodies were recorded an the benign elements and the carcinomas for both cytologic and histologic slides. Benign breast tissues demonstrated strong continuous immunostaining for cal ponin and SMMHC of MEG. The interlobular stromal cells as well as intralobu lar stromal cells showed no immunostaining with either antibody. In cytolog ic preparations, MEC staining with calponin and SMMHC appeared as spindle c ells between epithelial cells or along the edges of the epithelial groups. The bipolar stromal cells did not stain with either antibody. The tissues with DCIS (ductal carcinoma in situ) often showed the presence of MEC with strong calponin immunostaining, but sometimes the immunostainin g was discontinuous or entirely absent a,around markedly dilated ducts. The SMMHC antibody was invariably negative, with architectural DCIS in dilated ducts. Two cases of DCIS with prominent periductal fibrosis or inflammatio n were positive Sol calponin, but the pe,periductal stromal cells Mere calp onin- and SMMHC-negative. Invasive carcinoma was negative for both calponin and SMMHC, brit areas of DCIS were often positive in a discontinuous pattern. In conclusion, I) Benign cellular elements from breast tissue FNAB showed s trong continuous decoration of MEC with both calponin and SMMHC. Vascular p ericytes and vascular smooth muscle were positive for both antibodies, but these cells were not observed in the FNAB. Benign proliferative epithelium showed no local increase in MEC with either antibody Bipolar stromal cells in tissue and smears did not stain for MEC antibodies. 2) BSC did not corre spond morphologically to MEC, and were not decorated with calponin or SMMHC . 3) Calponin-positive MEC were commonly associated with in situ ductal les ions, although they map at limes have been discontinuous or absent entirely . DCIS may be recognized in FNAB by the presence of calponin-positive MEC a ssociated with tumor cell groups. 4) Invasive carcinomas were invariably ne gative for MEC with these antibodies. (C) 1999 Wiley-Liss, Inc.