Keratin 7 expression in lymph node metastases but not in the primary tumour correlates with distant metastases and poor prognosis in colon carcinoma.

Colorectal carcinoma (CRC) is one of the leading causes of cancer-related deaths worldwide. Alterations in keratin expression, including keratin 7 (K7), are frequent findings in multiple cancers, and they constitute a prognostic factor. The aim of our study was to evaluate the prognostic significance of K7 in the primary tumour and lymph node metastases in two separate cohorts of patients: the first one with lymph node involvement (LN+, 129 cases) and the second one free of LN metastases (LN-, 85 cases). Keratin 7 expression in CRC was analysed on tissue microarrays with immunohistochemistry and evaluated using the h-score. In the LN+ group K7 positivity was identified in 7/129 (5.4%) of primary tumours (PT) and lymph node metastases (LNM); concordance between them was 94% ( 0.396). Keratin 7 was expressed in 8/85 cases (9.4%) in the LN- group. K7 expression in LNM of the LN+ cohort correlated with shorter overall survival (OS) (p = 0.047) and presence of distant metastases at diagnosis (p = 0.005). Expression of K7 in the primary tumour in both cohorts did not correlate with survival. We conclude that the status of K7 expression in metastatic lymph nodes from CRC is a poor prognostic factor.