BMC Cancer 2006, 6:10 http://www.biomedcentral.com/1471-2407/6/10 Table 2: Tumour patient cases in this study Table 3: Expression profile of cytokeratins Age (mean) 58 years (range 31 – 90 years) No Expression postive Expression Sex Follow-up (mean) T stadium N stadium Grading 240 men, 68 women 64 months (range 4 – 181 months) 135 T1 tumours 125 T2 tumours 15 T3 tumours 33 T2 tumours 212 N0 lymph node negative 57 N1 lymph node positive carcinoma 39 N2 lymph node positive carcinoma 54 well differentiated tumours (G1) 214 moderately differentiated tumours (G2) 40 weakly differentiated tumours (G3) sion of the primary antibody) and positive controls were used throughout. The expression of Ck 5/6, Ck 8/18, Ck 1, CK 10, Ck 14, Ck 19 and vimentin were determined independently by two pathologists (HB and JP). Both pathologists determined the percentage of positive cells in each core. The percentage was classified for Cytokeratin 19 in 3 groups (0 % no Expression, 1:1–50% moderate expres- sion, 2 >50% high expression) and Ck 5/6, Ck 8/18, Ck 1, CK 10, Ck 14 and vimentin in two groups (0: no Expres- sion, 1: ≥1% positive expression). The mean percentage value of the two cores representing one tumour and were used for further evaluation. Statistical analysis The TNM-stage, the histological differentiation and the expression of Ck 5/6, Ck 8/18, Ck 1, CK 10, Ck 14, Ck 19 and vimentin were related to the duration of the progres- sion-free and the overall survival. The measurement of time started from the date of surgery to the date of histo- logically proven recurrent or metastatic carcinoma or dis- ease related death, respectively. Patients who died from intercurrent disease during the trial were censored at the date of death. Patients lost to follow-up were censored at the date of the last examination. Correlations between clinical features and the expression of cytokeratins were evaluated statistically by chi-square tests. The overall survival curves were constructed accord- ing to Kaplan and Meier [15]. The Log-Rank test was used to assess differences between groups and the multivariate survival analysis was performed with Cox regression [16], a p-value < 0.05 was considered to be significant. Results The series comprised 308 patients (240 men and 68 women) with a median age of 58 years (range 31–90). All Ck 5–6 Ck 14 0.045 0.021 0.026 0.037 Page 3 of 8 (page number not for citation purposes) Antibody CK 5/6 CK8/18 CK 1 CK 10 CK14 Ck 19 Vimentin 123 133 147 177 159 149 237 169 154 121 91 107 107 24 tumours were classified post surgically according to the TNM system [12]. Patients were clinically evaluated in our routine follow-up for 3–10 years. Clinical and tumour details of the patients with oral squamous cell cancer are shown in Table 2. On average 90 % of all cores could be evaluated for the expression of intermediate filaments. Immunohistochemical examination showed that Ck 8/ 18, Ck 5/6, Ck 1, CK 10, Ck 14, Ck 19 and vimentin reac- tivity was confined homogeneously to the cytoplasma of neoplastic cells. The expression levels did not differ signif- icantly for the vast majority of the cases between the two tumour cores representing one case, indicating a rather homogeneous expression. No correlation was found between Ck 1, Ck 5/6, Ck 10, Ck 14, vimentin and the sur- vival prognosis. Detectable levels of Ck 8/18 (Ck 8/18 ≥ 1%) were found in 54 % (154/287) of the oral SCCs. Detectable levels of Ck 19 (Ck 19 ≥ 1%) were found in 37,5% (96/256) of the cases, high levels of Ck 19 expression (Ck 19 > 50%) were found in 4,2% (11/256) of the investigated tumour spec- imens (Table 3). The immunohistochemical staining is shown in Figure 1. Ck 5/6 and Ck 14 were significantly correlated with the tumour size and lymph node status in the Chi-square Test (Table 4) and between each other (p < 0.01). No correla- tion was found between tumour size, tumour differentia- tion, lymph node status and the expression of Ck 8/18, Ck 1, Ck 10, Ck 19 and vimentin in Chi-square test. Log-rank test of Ck 8/18 and Ck 19 expression showed a significantly decreased overall survival of carcinomas with a Ck 8/18 expression (Ck 8/18 ≥ 1% (n = 154), p < 0.04, Table 4: Chi-square Test of Ck 5–6 and Ck 14 Prognosticator Node status P value Tumour size P value