We have read with great interest the paper of Salman et al. (2012), which appeared in the Egyptian Journal of Pathology, concerning the morphological and immunohistochemical characteristics of triple-negative breast carcinoma (TNBC) and basal breast carcinoma. In particular, the authors stressed that triple-negative as well as basal breast carcinomas exhibited some common morphological criteria, and, therefore, a positive immunostaining for CK5/6 and/or EGFR is needed to identify the basal neoplastic phenotype.
TNBC represents 10–17% of a heterogeneous subgroup of breast cancers, which are characteristically aggressive with high recurrence, metastatic, and mortality rates, in which the hormonal receptor and HER-2 antagonists are ineffective (Griffiths and Olin, 2012). Therefore, the prognosis of women with TNBC is significantly poor when compared with women with other subtypes of breast cancers (Dent et al., 2009). Consequently, greater efforts should be undertaken to identify the molecular subtypes of TNBC on the basis of immunohistochemical markers (Badve et al., 2011).
In this field, based on immunoreactivity, a cohort of 122 TNBC was recently classified into basal-like (CK5/6-positive and/or EGFR-positive), molecular apocrine (androgen receptor-positive and/or γ-glutamyl transferase-positive), claudin low (claudin 3-negative, 4-negative, and 7-negative and/or E-cadherin-negative), mixed (tumors belonging to two or more subtypes), and null (tumors not matching any other subtypes) types (Choi et al., 2012). In this study, using multivariate analysis, tumor cell discohesiveness was shown to be related to a shorter overall survival, and CK5/6 immunoreactivity and claudin 7 positivity were related with a shorter disease-free survival (Choi et al., 2012).
In addition, we would report herein our experience with a group of 72 patients (age range 32–92 years, mean 62.1) diagnosed with TNBC, none of whom received neoadjuvant/adjuvant chemotherapy or hormonal therapy. With regard to the histotype, all TNBC were represented by invasive ductal carcinomas not otherwise specified; the histological grade was recorded as follows: six (8.33%) carcinomas were of G1 grade, 30 (41.67%) were G2, and 36 (50%) were G3. Taking into consideration the neoplastic dimensions, 23/72 (32%) cases were recorded as T1, 39/72 (54.1%) as T2, 4/72 (5.5%) as T3, and 6/72 (8.4%) as T4. A total of 36 (50%) cases of TNBC were node-negative, whereas the other 36 (50%) were node-positive. pTNM showed that, among ductal invasive TNBC, 16/72 (22.2%) were stage I, 30/72 (41.6%) were stage II, 18/72 (25%) were stage III, and only 8/72 (11.2%) were stage IV. TNBC were defined by negative immunohistochemical testing for ER, PR, and also by negative testing for HER-2 amplification by fluorescence in-situ hybridization. From TNBC tissue blocks, 4-μm-thick parallel sections were cut, mounted on silane-coated glasses, and subjected to immunohistochemical procedures with the following antisera: KI-67 (w.d. 1 : 150, clone MIB-1; Dako Corporation, Glostrup, Denmark); DNA Topoisomerase IIα (w.d. 1 : 150, clone KI-S1; Dako Corporation); E-cadherin (w.d. 1 : 200, clone NCH 38; Dako Corporation); Androgenic Receptor (w.d. 1 : 100, clone AR 441; Dako Corporation); and Caveolin-1 (w.d. 1 : 500, Santa Cruz Biotechnology Inc., Santa Cruz, California, USA). The values of Ki-67 and Topoisomerase IIα (TOP IIα) were scored by counting the number of positively stained nuclei per 1000 malignant cells in up to 10 fields representative of the whole neoplastic portions (Tuccari et al., 1993). The cutoff values for Ki-67 and TOP IIα were determined by calculating the median (>10 for Ki-67 and>13 for TOP IIα). The E-cadherin (E-CAD) evaluation was classified as negative, weak, moderate, or intense; the latter two were considered positive. Androgenic receptor positivity was defined as at least 10% positive neoplastic cells with nuclear staining, similar to what has been reported in the study by Choi et al. (2012). The caveolin-1 (CAV-1) immunostaining intensity was graded as follows: 0, negative; 1, weak; 2, moderate; and 3, strong. The stained area recorded as the percentage of positive cells was rated as follows: 0 (0≤10%), 1 (11–25%), 2 (26–50%), 3 (51–75%), and 4 (>75%), according to procedures described elsewhere (Barresi et al., 2006). Progression-free survival (PFS) was defined as the time interval (months) from the date of the first diagnosis to the date of the first locoregional relapse or systemic metastasis. Overall survival (OS) was calculated from the date of the first curative surgery to the date of the last follow-up or death because of any cause. The possible correlations between immunohistochemical data and clinicopathological characteristics of TNBC were investigated using nonparametric methods (χ2-test). Kaplan–Meier analysis and long-rank statistics were utilized to evaluate PFS and OS. Multivariate regression analysis was performed using the Cox method. A P value less than 0.05 was considered statistically significant. Data were analyzed using the SPSS package, version 12.0 (SPSS Inc., Chicago, Illinois, USA).
An increased growth fraction [≥10% Ki-67 labeling index (LI)] was found in 42/72 patients (58.3%), whereas a low Ki-67 LI was encountered in the other 30 patients (41.7%). The immunoexpression of TOP IIα was elevated (≥13%) in 40/72 (55.5%) patients, and a low expression was observed in 32 patients (44.5%). Androgen receptor (AR) immunoreactivity was observed in 26 patients (36.2%), whereas an absence of immunostaining was observed in 46 patients (63.8%). A high ID score (4–9) for CAV-1 was demonstrated by 45/72 patients (72.5%); 27/72 patients (37.5%) showed a low ID score (0–3). An evident, moderate, or intense immunopositivity for E-CAD was appreciable in 29 patients (40.3%); a negative or slightly focal immunostaining was reported in 43 patients (59.7%). On the basis of immunohistochemistry results, the analysis of TNBC, performed case by case, suggests the identification of two different immunoprofiles in terms of prognosis: the first, a highly proliferative/aggressive (Ki-67 LI≥10%; TOP IIα≥13%; CAV-1 ID score 4–9; AR and E-CAD-negative) profile and the second, a nonhighly proliferative/aggressive (Ki-67 LI<10%; TOP IIα<12%; CAV-1 ID score 0–3; AR and E-CAD-positive) profile. Statistical analysis documented a positive correlation between Ki-67 LI and the grade or TOP IIα expression with significant P values (P=0.02 and P<0.001, respectively). Using multivariate analysis, the neoplastic stage (P=0.011) and CAV-1 immunoreactivity (P=0.036) emerged as independent prognostic parameters significantly related to OS. When patients were stratified according to the immunoprofile, those with a highly proliferative/aggressive carcinoma showed the worse prognosis in terms of OS and PFS.
In conclusion, taking into consideration our present observations as well as data from the recent literature (Choi et al., 2012; Griffiths and Olin, 2012), we suggest that further research on TNBC should be addressed to identify the peculiar immunophenotype of this aggressive group of breast cancer to allow development of new targeted molecular therapeutic options.
Conflicts of interest
There are no conflicts of interest.
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