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Aims: Invasive micropapillary carcinoma of the breast is an aggressive and distinctive variant of breast cancer. These tumours have a characteristic histological appearance and have been associated with a high incidence of axillary lymph node metastases and a poor clinical outcome. The aims of this study were to investigate the immunohistochemical profile of invasive micropapillary carcinoma of the breast, to compare it with invasive ductal carcinoma, and to identify the morphological parameters which predict its poor outcome., Methods and Results: Fifty-three (2.6%) invasive micropapillary carcinomas of the breast from 2022 cases of infiltrating breast carcinomas were identified by retrospective review. The patient age at presentation ranged from 33 to 78 years (mean 52.5 years). The tumour size ranged from 5 to 70 mm (mean 27 mm). Eighty-two percent (43 of 53) were of high histological grade; 69% (33 of 48) of cases with axillary lymph node dissections had positive lymph nodes; and 75.5% (40 of 53) had lymphatic invasion: 46% (22 of 48) of cases had extranodal extension. Of lymph node-positive cases, 61% had four or more metastatic lymph nodes. Of tumours with tumour size >10 mm, 77% had positive lymph nodes. The percentages of cases positive for oestrogen receptor (ER) and progesterone receptor (PR) were 68% and 61%, respectively. These values were significantly higher than the values for invasive ductal carcinomas. p53 and c-erbB-2 were detected in 48% and 54% of cases, respectively. The mean value of Ki67 was 26%. Follow-up was available in 36 patients. Eight patients had local recurrences, nine patients had distant metastases, and 10 patients died of disease within a follow-up period of 9 years., Conclusion: Lymphotropism and an unfavourable prognosis are the hallmarks of this distinct entity. Prognostic markers such as ER, PR, p53, and c-erbB-2 failed to provide new criteria to allow discrimination of these tumours from other breast cancers.

Invasive micropapillary carcinoma of the breast is an uncommon variant of infiltrating ductal carcinoma. Observing its distinctive cytologic appearance and aggressive behavior is important for early diagnosis by fine-needle aspiration cytology (FNAC). There are only a few reported cases in the literature. Five women presented with breast masses. FNAC showed malignant epithelial tumors, and mastectomy materials showed invasive micropapillary carcinoma for all of them. Three patients had axillary lymph node metastases. Invasive micropapillary carcinoma, with its angulated papillary clusters lacking a fibrovascular core, and irregular crowded nuclei, has a distinctive cytologic appearance which correlates with its histological features. A differential diagnosis from other primary or metastatic papillary lesions of the breast may be possible using immunohistochemistry and some cytologic features. The limited experience with invasive micropapillary carcinoma should not discourage others from undertaking further studies., (Copyright 2002 Wiley-Liss, Inc.)