Venous invasion demonstrated by orcein staining of colorectal carcinoma specimens is associated with the development of distant metastasis.

To assess venous invasion (VI) and its relation to distant metastases in colorectal cancer (CRC). Primary untreated CRC cases were assessed for VI. All tumour blocks were stained with H&E and orcein. The presence of VI and nodal status were then correlated with the presence of synchronous or metachronous distant metastases. VI was detected more frequently with the orcein stain (18% versus 71%). Eleven tumours (nine node-positive tumours, all VI positive) were associated with synchronous distant metastasis. During a median follow-up of 17 months nine further cases were diagnosed with distant metastasis (six node-positive tumours, all VI positive). The specificity and sensitivity of the presence of nodal metastasis for predicting distant metastasis were 0.56 and 0.75, respectively. The same values for orcein-detected VI were 0.39 and 1, respectively. Elastic stains such as the orcein stain enable the detection of clinically relevant VI with greater frequency than conventionally stained histological slides. If nodal involvement is an indication for systemic chemotherapy, the data presented here suggest that VI detected by the orcein stain should also be an indication for systemic chemotherapy.