Mucin histochemical analysis of the ileocaecal valve and lymphoid tissues of the terminal ileum: role against tumour invasion.

OBJECTIVES

We previously reported clinicopathological data on 78 patients who underwent a right hemicolectomy from 1990 to 1997. Our results indicated that the ileocaecal valve [ICV] and lymphoid tissue of the terminal ileum might, together, play a protective and local immune role against carcinoma invasion. Furthermore, we previously reported that mucin histochemical features of the transitional zone [TZ] might also play a role in predicting metastasis and, thus, prognosis. The aim of this study was to examine the clinicopathological correlation between lymphoid infiltration and mucin secretion in the terminal ileum with carcinoma of the right colon.

METHODS

According to the proximity of the tumour to the ICV, a total of 16 specimens with lymphoid infiltration to and around [< 1 cm] the ICV were studied in order to identify the mucin expression and histochemical features of the TZ as a prognostic indicator.

RESULTS

Patients with sulphomucin-staining tumours in the terminal ileum and ICV had a relatively favourable course. Even when the clinical staging was the same for different tumours, greater lymphoid infiltration in the ICV, greater staining for sulphomucin in the ICV and a relatively favourable course were observed in nine patients. The sulphomucin-type TZ showed a favourable course as well. On the other hand, patients with sialomucin staining of the ICV and the TZ tended to have low-grade lymphoid infiltration and a very poor course, although two patients with moderately high-grade lymphoid infiltration had a favourable course. Overall survival was significantly associated with the mucin type of the ICV [p < 0.01].

CONCLUSIONS

Our results indicated that lymphoid infiltration of the terminal ileum may lead to an alteration in mucin secretion and, thus, play a protective role in the invasive and metastatic process of advanced right colon carcinoma.