Zagouri et al. BMC Cancer 2010, 10:409 http://www.biomedcentral.com/1471-2407/10/409 Table 1 Algorithm for the calculation of the Allred score [17,18] Observed values Percentage of positive cells None <1% 1% to 10% 10% to 33.3% 33.3% to66.7% more than 66.7% Intensity of staining weak intermediate strong “Allocated” values for the calculation of the 0-8 Allred score 0 1 2 3 4 5 1 2 3 Results The description of the study sample is presented in Table 2. Hsp90 exhibited mainly cytoplasmic immunor- eactivity in epithelial cells of normal breast (ducts and lobules) (Figure 1), and ILC (Figure 2). Some epithelial cells of ILC also showed nuclear staining; nevertheless, all ILC foci mainly presented with a positive cytoplasmic immunoreaction for Hsp90. The positive cell percentage and the staining intensity were evaluated. The percentage of Hsp90 positive cells, the intensity of Hsp90 staining, as well as the Allred score are presented in detail in Table 3 and Table 4. Concerning ILC, the inter-observer agreement was 90.6% for Hsp90 intensity (kappa = 0.8289, p < 0.0001, rejecting the hypoth- esis of random ratings) and 81.3% for Hsp90 percentage (kappa = 0.7780, p < 0.0001, rejecting the hypoth- esis of random ratings). A statistically significant decrease in Hsp90 expression, both in terms of positive cells(%) and Allred score, was noted (74.2 ± 11.2 vs. 59.1 ± 14.2 p = 0.0001; 7.00 ± 0.95 vs. 6.22 ± 1.01, p = 0.007, Wilcoxon matched-pairs signed- ranks test). The decrease in Hsp90 intensity (2.16 ± 0.68 vs. 1.84 ± 0.63) was of borderline statistical significance (p = 0.087, Wilcoxon matched-pairs signed-ranks test). Null association was noted between Hsp90 Allred score and ER positivity (6.40 ± 0.55 for ER negative cases vs. 6.19 ± 1.08 for ER positive cases, p = 0.547, Mann-Whit- ney-Wilcoxon test for independent samples), PR positiv- ity (6.43 ± 0.98 for PR negative cases vs. 6.16 ± 1.03 for PR positive cases, p = 0.532, same test), c-erbB2 status (6.20 ± 1.04 for c-erbB2 negative cases vs. 6.29 ± 0.95 for c-erbB2 positive cases, p = 0.904, same test) as well as Ki-67(%) (Spearman’s rho = -0.083, p = 0.651). Discussion To our knowledge, this is the first study to demonstrate a significantly decreased Hsp90 expression in infiltrative Page 3 of 6 lobular carcinomas, both in terms of percentage and Allred score. This finding could be viewed in a wider context; the present findings are consistent with those previously described by our team on precursor lobular lesions (LN). The persistent downregulation of Hsp90 expression throughout the whole lobular series (at the precursor and invasive components) may be contrary to what might have been expected; it is known that Hsp90 over- expression is a feature of invasive ductal carcinomas [5-7]. It is thus tempting to speculate that the whole lobular series may display a discrete, less intense profile of Hsp90 expression, which differentiates itself from the marked upregulation in ductal carcinomas. The underlying mechanisms of this discrepancy remain elusive. ILC express c-erbB2 at a far less extent than ductal carcinomas [19]. Given that c-erbB2 has Table 2 Characteristics of patients and histological features of invasive lobular carcinomas. Categorical Variables Menopausal status Premenopausal Postmenopausal First-degree relative with breast cancer Yes No Breastfeeding Yes No Grade 1 2-3 Tumor diameter <2 cm ≥2 cm Nodal status Positive Negative Metastasis Yes No ER status Positive Negative PR status Positive Negative c-erbB2 status Positive Negative Continuous variable Ki-67 (%) Frequency (%) 8 (25.0) 24 (75.0) 6 (18.8) 26 (81.2) 24 (75.0) 8 (25.0) 5 (15.6) 27 (84.4) 6 (18.8) 26 (81.2) 8 (25.0) 24 (75.0) 0 (0.0) 32 (100.0) 27 (84.4) 5 (15.6) 25 (78.1) 7 (21.9) 7 (21.9) 25 (78.1) mean ± SD 12.0 ± 5.1