直肠的解剖和分期.ppt

Depth of invasion outside the muscularis propria. (a) Orthogonal high-resolution T2-weighted MR image shows tumor extension through the muscularis propria at multiple points (black arrows). The residual muscularis propria is seen as a subtle hypointense line (white arrow). The maximum depth of invasion outside the muscularis propria is approximately 5 mm. (b) Orthogonal high-resolution T2-weighted MR image obtained in a different patient shows significant tumor infiltration (black arrow) beyond the muscularis propria (white arrow). Arrowhead = mesorectal fascia. * Relationship of tumor to the mesorectal fascia. (a) Orthogonal axial high-resolution T2-weighted MR image shows a tumor that infiltrates into the mesorectal fat (arrow) but does not involve the mesorectal fascia. Double-headed arrow = distance between leading edge of tumor and mesorectal fascia. (b) Orthogonal axial high-resolution T2-weighted MR image shows tumor infiltration (arrow) through the anterior rectal wall and into the mesorectal fat. The tumor abuts the mesorectal fascia posterior to the prostate gland (arrowhead). * The assessment of lymph node involvement in primary rectal cancer involves evaluation of the following nodal groups: mesorectal, superior rectal, and inferior mesenteric; internal, external, and common iliac; retroperitoneal; and superficial inguinal * Drawing illustrates the most common nodal pathways of tumor spread in rectal cancer. The most common pathway of nodal spread from all primary rectal tumors is to mesorectal nodes, followed by spread to superior rectal and inferior mesenteric nodes. Midrectal tumors also spread through lymphatic vessels along the midrectal vessels to internal iliac nodes, whereas low rectal tumors may also involve superficial inguinal nodes. * Features that are suggestive of malignancy include irregular or spiculated nodal margins and heterogeneous signal intensity * Mesorectal lymph node involvement. (a) Coronal high-resolution T2-weighted MR imag