MRI-detected extramural venous invasion of rectal cancer: Multimodality performance and implications at baseline imaging and after neoadjuvant therapy

Abstract

MRI is routinely used for rectal cancer staging to evaluate tumor extent and to inform decision-making regarding surgical planning and the need for neoadjuvant and adjuvant therapy. Extramural venous invasion (EMVI), which is intravenous tumor extension beyond the rectal wall on histopathology, is a predictor for worse prognosis. T2-weighted images (T2WI) demonstrate EMVI as a nodular-, bead-, or worm-shaped structure of intermediate T2 signal with irregular margins that arises from the primary tumor. Correlative diffusion-weighted images demonstrate intermediate to high signal corresponding to EMVI, and contrast enhanced T1-weighted images demonstrate tumor signal intensity in or around vessels. Diffusion-weighted and post contrast images may increase diagnostic performance but decrease inter-observer agreement. CT may also demonstrate obvious EMVI and is potentially useful in patients with a contraindication for MRI. This article aims to review the spectrum of imaging findings of EMVI of rectal cancer on MRI and CT, to summarize the diagnostic accuracy and inter-observer agreement of imaging modalities for its presence, to review other rectal neoplasms that may cause EMVI, and to discuss the clinical significance and role of MRI-detected EMVI in staging and restaging clinical scenarios.

Keywords: Disease-free survival; Extramural venous invasion; Magnetic resonance imaging; Prognosis; Rectal Neoplasms.

Fig. 1

Venous anatomy of the rectum. The upper 2/3 of the rectum drains via the superior rectal vein (A SRV) into the inferior mesenteric vein (B IMV). The lower 1/3 of the rectum drains via the middle (a MRV) and inferior rectal vein (a’ IRV) into the internal iliac vein (b IIV), common iliac vein (c CIV), and inferior vena cava (d IVC)

Fig. 2

Extramural venous invasion on histopathology. a The tumor cells (asterisk) are surrounded by a vessel on hematoxylin–eosin stain. b Elastin stain is helpful to depict extramural venous invasion (asterisk) by highlighting elastin fiber (arrowheads) around tumor cells. The scale bar is 500 µm

Fig. 3

Extramural venous invasion on T2-weighted image. A nodular-shaped structure (a arrow) arising from the ulcer crater and leading edge of the primary lesion (a asterisk) invades the mesorectal fascia (a arrowhead). The structure also  extends cranially in the mesorectal fascia (b arrow) and is branched (c arrows)

Fig. 4

Extramural venous invasion scoring system based on T2-weighted images. a No vessel exists adjacent to the primary tumor (score 0). b Normal diameter vessel adjacent to the primary tumor demonstrates no tumor signal intensity (score 1). c Slightly expanded vessel without abnormal signal intensity (score 2). d Expanded vessel including obvious tumor signal intensity (score 3). e Expanded vessel with irregular or nodular contour containing tumor signal intensity (score 4). Adapted from Smith NJ, et al. Br J Surg 2008 [22]

Fig. 5

Extramural invasion on diffusion weighted imaging. A 41-year-old man with rectal adenocarcinoma. T2-weighted image demonstrates a distended perirectal vessel with a lack of flow void and central tumor signal intensity which is contiguous with the primary rectal tumor (a arrow). Diffusion-weighted image shows a high signal intensity cord-like structure contiguous with the primary rectal tumor (b arrow)

Fig. 6

Extramural invasion on contrast-enhanced T1-weighted image. A 56-year-old male with rectal adenocarcinoma. The dilated vessel which is in continuity with the tumor has an irregular margin and contains intermediate signal intensity rather than flow void on the T2-weighted image (a arrow). The tumor in the vessel enhances on the contrast-enhanced T1-weighted image (b arrow)

Fig. 7

Extramural venous invasion on CT. A 47-year-old female with rectal adenocarcinoma. A nodule with an irregular margin containing intermediate signal intensity is observed in the mesorectum on axial T2WI (a arrow). Sagittal T2WI reveals a cord-like structure with tumor signal intensity in the superior rectal vein (b arrow) which drains to the inferior mesenteric veins (b arrowheads) Similarly, contrast-enhanced CT demonstrates an enhancing irregular nodule within the posterior mesorectum on the axial image (c arrow). On the sagittal image a cord-like nodular mass is contiguous with the dilated superior rectal vein (d arrow) and inferior mesenteric veins (d arrow heads) on the sagittal image. The diameters of the inferior mesenteric and superior rectal veins are 8.5 mm (e arrow) and 4.8 mm (f arrow), respectively, which is suggestive of the presence of EMVI

Fig. 8

Local recurrence after surgery from residual disease associated with positive circumferential margin due to extramural venous invasion. A 58-year-old man with rectal cancer. T2-weighted (a) and postcontrast (b) coronal image before treatment demonstrate nodular-shaped structure (black arrows) on the right extending to the mesorectal fat tissue, and worm-shaped (white arrows) structure on the left with tumor signal intensity arising from the primary lesion, indicating extramural venous invasion (EMVI) extending the mesorectal fascia (arrow heads). Axial T2-weighted image shows a primary tumor (c asterisk) and an irregular tumoral deposit in and abutting the mesorectal facia near the left pelvic sidewall (c arrow). Axial and coronal ¹⁸F-FDG-PET/MRI images 23 months after surgery following neoadjuvant therapy show FDG avidity corresponding to a developed nodular recurrence at the same location (d–f arrows)

Fig. 9

Extramural venous invasion in mucinous adenocarcinoma. A 53-year-old man with rectal mucinous adenocarcinoma. The circumferential rectal tumor shows high signal intensity on coronal T2WI (a asterisk). Peripheral heterogeneous enhancement is observed on contrast enhanced T1WI (b asterisk). The intravenous component demonstrates signal intensity and enhancement similar to the primary lesion (a, b arrows)

Fig. 10

Extramural invasion in squamous cell carcinoma. A 58-year-old male with rectal squamous cell carcinoma. A nodular, elongated structure extends cranially from the right side of the circumferential rectal tumor (a, b arrow)

Fig. 11

Extramural venous invasion in neuroendocrine tumor. A 50-year-old man with poorly differentiated neuroendocrine tumor, large-cell type. On the T2WI a tubular structure with irregular margins and signal intensity similar to the tumor (a arrow) extends from the rectal mass (a asterisk). The primary lesion (b asterisk) and extramural venous invasion (b arrow) are more conspicuous on DWI. Mesorectal lymph nodes which were histopathologically proven to be nodal metastases are depicted on T2WI and DWI (a, b arrowheads)