[The value of immunohistochemical expression of Ki-67 and CD34 in differentiating ductal carcinoma in situ from ductal carcinoma in situ-like invasive breast cancer].

To investigate the expression of Ki-67 and CD34 in the differential diagnosis of ductal carcinoma in situ (DCIS) and DCIS-like invasive breast cancer (DLIBC). A total of 100 cases of DCIS and 150 cases of DLIBC diagnosed pathologically in Yantai Yuhuangding Hospital from January 2019 to March 2022 were collected. The expression of p63, CK5/6, Ki-67 and CD34 in both groups were detected by immunohistochemical (IHC) staining and evaluated. The 100 cases of DCIS included 11 cases of low-grade DCIS, 28 cases of intermediate-grade DCIS and 61 cases of high-grade DCIS. IHC staining of p63 and CK5/6 showed the myoepithelial cells around cancerous duct were complete or partial absence. Ki-67 expression showed two patterns: high expression in the basal layers and scattered expression within the tumor. Most cases showed mainly high basal expression (77/100, 77%), and the proportion of this pattern was significantly different between low grade and high grade DCIS (<0.05). All cases showed complete CD34 expression surrounding the cancerous duct with different proportion (vascular necklace) suggested small vessels proliferation. The 150 cases of DLIBC included 142 cases of invasive ductal carcinoma (IDC) (three cases of basal-like breast cancer was included), two cases of secretory carcinoma, three cases of solid papillary carcinoma, two cases of adenoid cystic carcinoma and one case of acinar cell carcinoma. Among 142 cases of IDC, 13 cases were grade Ⅰ, 77 were grade Ⅱ and 52 were grade Ⅲ. IHC staining of p63 showed complete absence of myoepithelium. CK5/6 was negative in most cases and only positively expressed within the tumor in 3 cases of basal-like breast cancer. Ki-67 indicated a scattered expression pattern within the tumor. In most cases, CD34 immunostaining showed scattered positive blood vessels within the tumor while only two cases showed incomplete expression of CD34 around the tumor (2/150, 1.3%). The different expression patterns of Ki-67 and CD34 in DCIS and DLIBC was statistically significant (<0.05). The different expression patterns of Ki-67 and CD34 are helpful to distinguish DLIBC from DCIS. The appearance of "vascular necklace" with CD34 and the high expression of Ki-67 around the cancerous duct highly support the diagnosis of DCIS, and the scattered expression pattern of CD34 supports DLIBC.