Mucin 2 (MUC2) and mucin 5 (MUC5) expression is not associated with prognosis in patients with radically resected ampullary carcinoma

Mucins are glycoproteins that are common on the surfaces of many epithelial cells. Under normal circumstances, mucins are known to play a protective role for epithelial tissues. In addition, their involvement in the differentiation of the epithelium, modulation of cell adhesion, as well as cell signalling has also been proposed.¹ Two main families can be distinguished: secreted mucins or gel‐forming mucins (MUC2, MUC5AC, MUC5B, MUC6), and membrane‐bound mucins (MUC1, MUC3, MUC4, MUC12, MUC17).² Alterations in the expression and in the structure of mucins have been reported in both pre‐neoplastic and neoplastic lesions.³ The production of MUC2 or MUC5AC has been correlated, by a majority of non‐invasive type tumours, with the expansive growth of the tumours that display lower levels of invasion and metastasis.⁴ A broad histomorphological spectrum of ampullary carcinomas of Vater make a reproducible histological classification difficult. Ampullary carcinomas positive for MUC2 have been associated with intestinal type tumour, whereas MUC5AC‐positive ampullary carcinomas were related to pancreaticobiliary type.⁵,⁶,⁷ In ampullary carcinoma, immunohistochemical expression of MUC2 and MUC5 has never been correlated with survival of patients.

In order to investigate the potential prognostic role of MUC2 and MUC5 expression in ampullary carcinoma, we included in the present report 45 consecutive patients with radically resected ampullary cancer. All patients underwent surgical resection for tumours of ampullary origin; only those with no macroscopic residual disease were considered suitable for the study. Pathological findings (tumour size and spread, and lymph node status) were obtained from the pathologists' original reports and were reassessed by our pathologists. Survival was defined as from the date of initial surgery to the date of death or the last contact. Follow‐up data were available for all included patients.

The formalin‐fixed, paraffin‐embedded samples were sectioned at 5 μm and stained with H&E. The histological diagnoses were re‐examined by two independent pathologists. In addition, the most representative blocks of each patient were selected to be cut into new 5 μm‐thick sections for immunohistochemical studies. Immunohistochemical staining was performed by the streptavidin–biotin method. Expression of MUC2 and MUC5 was detected using two monoclonal antibodies: MUC1 (Dako) and MUC5 (Dako). Deparaffinised sections were incubated for 40 min with each primary monoclonal antibody. The expression of MUC2 and MUC5 was assessed according to the percentage of immunoreactive cells in a total of 1000 neoplastic cells (quantitative analysis). Immunoreactivity was graded as follows: positive, more than 5% of carcinoma cells stained; negative, no detectable staining or <5% of carcinoma cells stained. Known positive and negative tissue controls were included with each series. A univariate survival analysis for each prognostic variable on overall survival was estimated by the Kaplan–Meier method.⁸ The terminal event was death, attributable to cancer or non‐cancer causes. The statistical significance of the differences in survival distribution among the prognostic groups was evaluated by the log‐rank test⁹; p<0.05 was regarded as significant in two‐tailed tests. SPSS V.10 (SPSS, Chicago, IL, USA) was used for statistical analysis.

The cohort of patients consisted of 45 patients with pathological diagnosis of ampullary cancer (23 men and 22 women) undergoing pancreaticoduodenectomy. Median age at diagnosis was 63.1 years (range 36–80). Seventeen patients were node positive and 28 were node negative. The median duration of follow‐up after surgery was 46 months (range 13–102). Median overall survival was 44 months (range 6–100) and the 1, 3, and 5 year overall survival was 88.8%, 28.8% and 24.4% respectively. After a median follow‐up of 46 months, 27 patients (60.0%) are still alive without evidence of disease, 2 patients (4.4%) are alive with recurrence of disease and 16 patients (35.5%) are dead (12 died because of ampullary carcinoma). Adjuvant radiotherapy and/or chemotherapy for ampullary cancer was not routinely offered in the hospitals involved in the study.

To determine the prognostic impact of MUC2 and MUC5 protein expression by univariate survival analysis, patients were stratified according to the dichotomised variables (criteria as stated above) into MUC2 and MUC5 negative versus MUC2 and MUC5 positive groups. By univariate analysis, overall survival was not influenced by MUC2 or MUC5 expression (p = 0.2004 and 0.7248, respectively). In particular, the median survival time in patients with negative MUC2 expression was 53.55 months (95% CI 54.78 to 88.33 months) versus 69.00 months (95% CI 20.42 to 131.58 months) in patients with positive MUC2 expression. Median survival time in patients with negative MUC5 expression was 58.31 months (95% CI 38.87 to 77.75 months) versus 67.00 months (95% CI 62.90 to 71.10 months) in patients with positive MUC5 expression.

There is little substantial data reporting significant prognostic markers for ampullary cancer patients. An increasing interest in oncology research is now focused on the study of mucins in ampullary cancer, as molecular markers useful for a correct histological classification.⁵,⁶ For these reasons, for the first time in the literature, we have attempted to characterise the expression examining the possible prognostic significance of MUC2 and MUC5 in a homogeneous cohort of patients with radically resected cancer of the ampulla of Vater. The present study reports the absence of a prognostic role of mucin expression in this type of cancer.