BACKGROUND Micropapillary carcinoma (MPC) is known to have a worse prognosis than the other subtypes of breast cancer.
Occasionally, MPC is observed in association with invasive ductal carcinoma not otherwise specified (IDC NOS), as well as mucinous carcinoma. METHODS We examined the immunohistochemical expression of an estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (HER2) in 127 cases of surgically resected MPC or IDC NOS with MPC. Further, we classified these cases based on their immunohistochemical profile. RESULTS Among the IDC NOS with MPC cases, 47 were luminal A (62.7%), 10 were luminal B (13.3%), and 9 were HER2 (12.0%).
The MPC cases included 4 luminal A (50.0%), 2 luminal B (25.0%) and 1 HER2 (12.5%) subtypes. Of the mucinous carcinomas with MPC, 4 were grouped as luminal A (57.1%), 1 as luminal B (14.3%), and 2 as HER2 (28.6%) subtypes.
However, among the mucinous carcinomas, 33 were categorized as luminal A (89.2%), 3 as luminal B (8.1%), and 1 as HER2 (2.7%) subtype, indicating a low incidence of HER2 subtype as compared to the other subtypes. CONCLUSIONS The luminal B and HER2 subtypes were prevalent in carcinomas with MPC. This result explains the poor prognosis of breast carcinomas with an MPC pattern.
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Invasive micropapillary carcinoma is a recently defined unusual variant of invasive breast carcinoma characterized by the formation of micropapillae within clear spaces separated by delicate fibrocollagenous stroma. This study was designed to examine clinicopathologic features of invasive micropapillary carcinoma of the breast. Sixteen cases of invasive micropapillary carcinoma were retrieved from the files of the Department of Pathology, Yeungnam University College of Medicine. We evaluated their clinicopathologic findings including patients' age, tumor size, nuclear grade, vascular invasion, axillary lymph node status, presence of extensive intraductal carcinoma, estrogen and progesterone receptors, p53, c-erbB-2, MIB-1 labelling index and follow-up data and compared this results with those of 292 cases of invasive ductal carcinoma, not otherwise specified. The incidence of invasive micropapillary carcinoma was 4.2% of all invasive breast carcinoma, and the mean age of the patients was 46 years.
Nine cases were pure form (over 75% of micropapillary growth pattern in the tumor) and seven cases were mixed form. The results of clinicopathologic findings, except vascular invasion and axillary lymph node status, of the 16 cases of invasive micropapillary carcinoma were not different from those of the 292 cases of invasive ductal carcinoma, not otherwise specified (p>0.05). However, the rate of vascular invasion and axillary lymph node metastasis was significantly higher in invasive micropapillary carcinoma (p <0.05). Of 16 cases, five cases had distant metastasis during follow-up period, and one patient died of cancer.
Although the mechanism of higher vascular invasion and lymph node metastasis in micropapillary growth pattern could not be determined, we propose that invasive micropapillary carcinoma should be recognized as a separate entity with increased risks of vascular invasion and axillary lymph node metastsis.
Invasive micropapillary carcinoma (IMPCa) is a rare variant of invasive ductal carcinoma of the breast. This variant is associated with a set of peculiar cytological findings and aggressive biological behaviors. In most reported cases, IMPCa has involved massive axillary lymph node metastases at the time of diagnosis. We experienced four cases of cytological features of IMPCa, all of which were verified by histological examination. Fine needle aspiration cytology (FNAC) revealed malignant epithelial cells, which formed small, oval to angulated papillary clusters, which lacked central fibrovascular cores. The histological findings of the four cases revealed both pure and mixed forms of IMPCa, composed of cohesive malignant epithelial cells, surrounded by distinctive clear spaces and separated by thin fibrous septa. All patients evidenced axillary lymph node metastases at the time of diagnosis. It is important to identify the peculiar cytological findings which would differentiate IMPCa from other diseases.
Invasive micropapillary carcinoma (IMPC) of the breast is recently described rare variant of invasive ductal carcinoma. This variant has a distinctive histological features and aggressive biological behavior. We reviewed the cytologic features of eight cases of IMPC. The cytologic smears showed moderate to high cellularity and the tumor tissue was composed of atypical, angulated, cohesive clusters of neoplastic cells with a papillary to tubuloalveolar architecture, and a morular growth pattern without fibrovascular cores was seen on the histopathology. IMPC of the breast has distinctive cytologic features and it is important to make an early diagnosis via fine needle aspiration cytology due to this tumor's aggressive behavior.