[Molecular subtypes of breast cancer: prognostic implications and clinical and immunohistochemical characteristics]. / Subtipos moleculares del cáncer de mama: implicaciones pronósticas y características clínicas e inmunohistoquímicas.

BACKGROUND: Breast carcinomas are a heterogeneous group of tumours, in both their clinical behavior and their prognosis. The aim of this article is to classify breast carcinomas according to molecular subtypes by means of immunohistochemical markers and to analyse the clinicopathological and immunohistochemical characteristics and the patterns of survival and relapse of the different subtypes. METHODS: Two hundred and seventy-two patients diagnosed with breast cancer were classified into five subtypes: breast carcinomas of the basal type, HER2 type, luminal A type, luminal B type and normal. RESULTS: The most frequent breast carcinomas were: luminal A type carcinomas (62.5%), luminal B type carcinomas (18%), HER2 type carcinomas (9.9%), basal type carcinomas (8.4%) and normal phenotype carcinomas (1.4%). Significantly and with greater frequency, the luminal type breast carcinomas proved to be well differentiated tumours, of small tumoral size, with negative axillary ganglions, at an early stage at the time of diagnosis, with high levels of BCL-2 and a low Ki-67 proliferation index. On the contrary, the basal type and HER2 carcinomas presented larger tumours, poorly differentiated, greater ganglionar involvement and more advanced stages at the time of diagnosis. They expressed high Ki-67 proliferation indexes with greater frequency and were the subtypes that showed a worse prognosis on global survival and progression-free survival curves. CONCLUSION: Breast cancer classification based on immunohistochemical (IHC) parameters makes a better prognostic definition possible. Both the basal type and the HER2 type breast carcinomas present more unfavourable histopathological and IHC characteristics, as well as a worse survival and less relapse time, while the luminal type breast carcinomas show more benign characteristics and a better prognosis.

The value of cytokeratin immunohistochemistry in the evaluation of axillary sentinel lymph nodes in patients with lobular breast carcinoma.

BACKGROUND: Cytokeratin immunohistochemistry (IHC) reveals a higher rate of occult lymph node metastases among lobular carcinomas than among ductal breast cancers. IHC is widely used but is seldom recommended for the evaluation of sentinel lymph nodes in breast cancer patients. OBJECTIVE: To assess the value of cytokeratin IHC for the detection of metastases in sentinel lymph nodes of patients with invasive lobular carcinoma. METHODS: The value of IHC, the types of metastasis found by this method, and the involvement of non-sentinel lymph nodes were analysed in a multi-institutional cohort of 449 patients with lobular breast carcinoma, staged by sentinel lymph node biopsy and routine assessment of the sentinel lymph nodes by IHC when multilevel haematoxylin and eosin staining revealed no metastasis. RESULTS: 189 patients (42%) had some type of sentinel node involvement, the frequency of this increasing with increasing tumour size. IHC was needed for identification of 65 of these cases: 17 of 19 isolated tumour cells, 40 of 64 micrometastases, and 8 of 106 larger metastases were detected by this means. Non-sentinel-node involvement was noted in 66 of 161 cases undergoing axillary dissection. Although isolated tumour cells were not associated with further lymph node involvement, sentinel node positivity detected by IHC was associated with further nodal metastases in 12 of 50 cases (0.24), a proportion that is higher than previously reported for breast cancer in general. CONCLUSIONS: IHC is recommended for the evaluation of sentinel nodes from patients with lobular breast carcinoma, as the micrometastases or larger metastases demonstrated by this method are often associated with a further metastatic nodal load.