ORIGINAL ARTICLES

Use of an elastic stain to show venous invasion in colorectal carcinoma: a simple technique for detection of an important prognostic factor

C J Howlett, E J Tweedie, D K Driman

Department of Pathology, London Health Sciences Centre and University of Western Ontario, London, Ontario, Canada

Correspondence to:
^{Correspondence to} Dr D K Driman, Department of Pathology, London Health Sciences Centre, 339 Windermere Road, London, Ontario N6A 5A5, Canada; ddriman{at}uwo.ca

Background: Venous invasion (VI) is an important prognostic factor in colorectal cancer; it is positively associated with visceral metastases and may affect the decision to treat with adjuvant therapy.

Aims: To evaluate whether an elastic tissue (Movat) stain facilitates identification of VI, the number of Movat-stained blocks needed to detect VI, and whether VI identified with a Movat stain is prognostically equivalent to VI identified on H&E-stained slides.

Methods: H&E-stained sections from colorectal carcinomas from the year 2000 (n = 92) were examined for VI and compared to Movat-stained slides. Clinical charts were reviewed to compare rates of metastases in VI-positive versus VI-negative patients.

Results: With the Movat stain, VI was identified in 44% of cases previously categorised as negative (p<0.001) on review of H&E slides alone. One Movat-stained section was often sufficient to identify VI, with a statistically significant benefit to performing multiple stains if necessary. In H&E sections, two clues helped identify VI: the "unaccompanied artery" sign, where large arteries were seen without an accompanying vein; and the "protruding tongue" sign, where smooth tongues of tumour extended into pericolic/rectal fat. Metastases were present in 61% of cases positive for VI compared to 35% in VI-negative cases (p = 0.03). 45% of cases positive for intramural VI only developed metastases (p = 0.39), while 65% of cases positive for extramural VI only developed metastases (p = 0.03).

Conclusions: Pathologists should look for morphological clues of VI in H&E stained sections; when VI is not apparent, an elastic tissue stain on all tumour blocks significantly improves identification of VI. Morphological clues include the "unaccompanied artery" and "protruding tongue" signs.

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