‘Orphan arteriole’ sign – a helpful clue in detecting extramural venous invasion in colorectal carcinomas

Abstract

Extramural venous invasion is an important feature to recognise in colorectal carcinoma, with significant implications for clinical management and prognosis. Nonetheless, extramural venous invasion is thought to be underreported by pathologists. The ‘orphan arteriole’ sign (also known as ‘orphaned artery’ sign) is where a tumour nodule is seen adjacent to an artery but an accompanying vein cannot be identified on H&E stain. The ‘orphan arteriole’ sign can be a helpful hint that extramural venous invasion is present. An elastin stain (EVG) and a smooth muscle actin (SMA) immu-nostain can be used to confirm the presence of a vein overrun by carcinoma. We retrospectively reviewed 71 consecutive cases of colorectal carcinomas (CRCs) diagnosed as Bankstown-Lidcombe Hospital in 2012. We included 45 cases of pT3 and pT4 CRCs, all of which were stained with EVG and SMA. Cases of pT0, pT1 and pT2 CRC were excluded (26 cases). We found that the ‘orphan arteriole’ sign was a helpful clue in identifying extramural venous invasion in five cases, two of which were initially reported as negative for extramural venous invasion. Extramural venous invasion is an important feature to recognise in colorectal carcinoma, with significant implications for clinical management and prognosis. Nonetheless, extramural venous invasion is thought to be underreported by pathologists. The ‘orphan arteriole’ sign (also known as ‘orphaned artery’ sign) is where a tumour nodule is seen adjacent to an artery but an accompanying vein cannot be identified on H&E stain. The ‘orphan arteriole’ sign can be a helpful hint that extramural venous invasion is present. An elastin stain (EVG) and a smooth muscle actin (SMA) immu-nostain can be used to confirm the presence of a vein overrun by carcinoma. We retrospectively reviewed 71 consecutive cases of colorectal carcinomas (CRCs) diagnosed as Bankstown-Lidcombe Hospital in 2012. We included 45 cases of pT3 and pT4 CRCs, all of which were stained with EVG and SMA. Cases of pT0, pT1 and pT2 CRC were excluded (26 cases). We found that the ‘orphan arteriole’ sign was a helpful clue in identifying extramural venous invasion in five cases, two of which were initially reported as negative for extramural venous invasion.