Colorectal carcinoma (CRC) is the second most common cause of cancer-related deaths in North America [1]. Invasion of tumor cells into lymphatic and blood vessels is an imperative step in the metastatic progression of CRC [[2], [3], [4], [5]] with venous invasion (VI) associated with 18-fold increased risk of lymph nodes metastasis [2]. The risk of distant metastasis appears to be significantly increased by VI [[3], [4], [5]]. The significance of extra-mural blood vessel invasion in predicting the biological behavior of CRC is well established [[6], [7], [8]]. The significance of intramural blood vessel invasion and lymphatic vessel invasion, however, is not as well established [8]. A meta-analysis performed in 2018 that included >8000 patients from 1199 papers concluded that intramural VI was significantly associated with decreased cancer-specific survival (HR: 1.6) [9]. A borderline effect was also observed on overall survival and local recurrence.

Conventionally, lymph node metastasis is used as the surrogate marker for classifying the risk of metastatic disease. A more direct measure would be to use VI, which is an independent predictor of hematogenous spread and mortality in CRC [10]. However, damaged muscular walls of the veins can render accurate detection of VI difficult with routine hematoxylin and eosin (H&E) slides [10]. That is why Dawson et al. are proponents of the use of routine elastin staining for detecting VI [10]. Not only does it improve VI detection by two to three-fold, but it also improves cancer survival prediction [10]. The authors found interest with the under-reporting of VI detection in Ontario, Canada [10]. They outlined a population-based survey of 361 Ontario pathologists that quantify the seemingly low VI detection rates [10]. Heightened awareness and emerging literature on the benefits of elastin staining increased its usage among pathologists in Ontario [10]. Seventy-two percent of those that have increased their usage of routine elastin stains felt that their VI detection rate has improved [10].

Improving VI detection is critical as its presence in stage II CRC can provide oncologists with additional information which could influence their decision to offer adjuvant chemotherapy to patients [10]. Thus, it is crucial to investigate methods that can facilitate the detection of vessel invasion in CRC specimens.