Figure 10.2. T1 anal cancer.
(a) Transaxial T2W1 and (b) transaxial STIR image showing lobulated intermediate signal intensity tumour mass less than 2.0 cm maximum dimension extending through anal wall (arrows); vagina (V).
(a) Transaxial T2W1 showing intermediate signal intensity tabulated tumour mass (arrows) between 2.0 cm and 5.0 cm maximum dimension largely filling ano-rectal lumen, (b) Transaxial T2W1 just above (a) showing circumferential spread of tumour in lower rectum (arrows).The muscle layer remains intact. (c) Sagittal T2WI showing cranio-caudal extent of tumour. Differentiation between tumour stage on the basis of maximum dimension can be difficult with infiltrative tumours with circumferential spread; bladder (B); prostate (P); seminal vesicles (SV); muscle layer (M).
(a) Transaxial T2W1 and (b) coronal T2W1 showing intermediate signal intensity, nonlobulated tumour
(arrows) between 2.0 cm and 5.0 cm maximum dimensions which extends to the anal verge. There is an incidental right adenexal cyst (asterisk).
Figure 10.5. T3 anal cancer.
(a) Transaxial T2W1, (b) coronal T2W1 and (c) sagittal T2W1 showing intermediate signal intensity tumour
(arrows) greater than 5.0 cm maximum diameter. Tumour has extended through the anal sphincter into the ischioanal fossa and extended to the anal verge. Internal sphincter (I); longitudinal muscle layer (L); external sphincter (E); ischioanal fossa (IAF).
(a) Transaxial T2W1 and (b) sagittal T2W1 showing large lobulated high signal intensity mass (arrows)
characteristic of a mucinous adenocarcinoma. Tumour has extended through the anal sphincter into the fat of the ischioanal fossa and buttock to abut onto the natal cleft, it also extends cranially into the lower rectum (asterisk). Natal cleft (NC); ischioanal fossa (IAF).
(a) Transaxial T2W1 and (b) coronal T2W1 showing high/intermediate signal intensity mass (T) extending anteriorly through the anal wall and recto/anovaginal septum to invade the left side of the vagina (arrows) and laterally to infiltrate the pelvic floor (arrowheads) but not extend into the ischioanal fossa. Note probable left inguinal lymph node metastases (asterisk) which are non-enlarged but show asymmetrical clustering and have similar signal characteristics to the primary tumour. Urethra (Ur); vagina (V).
Figure 10.8. N1 anal cancer.
Transaxial T2W1 showing lymph node metastases in the perirectal fat (arrows) and local spread of primary tumour to rectum (asterisk). Lymph nodes are not normally identified in the perirectal fat on MRI and should be regarded as pathological. Differentiation between malignant and hyperplastic nodes on the basis of size, is not reliable in this location. Nodes with central necrosis or a similar signal characteristic to the primary tumour, as in this case, favour malignant disease.
Figure 10.9. N1 anal cancer.
Transaxial T2W1 of the mucinous anal cancer (T) shown in Figure 10.6. The perirectal lymph node (arrow)
shows central high signal indicating a high probability of metastatic disease. Central lymph node high signal on T2W1 occurs with metastatic mucin secreting adenocarcinoma and cystic nodal necrosis in squamous cell carcinoma. A benign right inguinal node, with fat in the hilum (arrowheads) also returns high signal on T2W1. The eccentrically located fat usually indicates its benign significance but uncertainty can be resolved with fat suppressed (STIR) sequences.
Figure 10.10. N2 anal cancer.
Transaxial T2W1 showing enlarged intermediate signal intensity left inguinal lymph node (arrow). Note nodal signal intensity is slightly higher than primary tumour (arrowheads) due to its closer proximity to the surface phased array receiving coil.
Figure 10.11. N3 anal cancer.
Coronal T2W1 showing bilateral surgical obturator (internal iliac) lymph node metastases (arrows). Note infiltrating ano-rectal tumour (T).
(a) Transaxial T2W1 and (b) coronal T2W1 showing bilateral inguinal lymph node metastases (arrows). Note intermediate signal intensity of the primary tumour (T). On the right side, the node has a ragged margin (arrowheads) indicating extra-nodal tumour extension.
Coronal T1W1 showing enlarged interaortocaval lymph node (arrow) consistent with metastatic disease.
Metastases in this location are not described in the UICC staging classification but imply a poor prognosis.
Transaxial T1W1 showing enlarged interaortocaval lymph node (arrow), porta hepatis lymph node mass
(arrowheads) and liver metastasis (asterisk). Note the intrahepatic bile duct dilatation secondary to the obstructing porta hepatis
(a) Transaxial T2W1 and (b) coronal T2W1 showing circumferential spread of intermediate signal intensity tumour mass (arrows). There is transmural spread of tumour with a fluid and air-containing fistula (arrowheads) extending through the pubococcygeal portion of the levator ani muscle into the ischioanal fossa (IAF).
(a) Transaxial T2W1 and (b) sagittal T2W1 showing marked oedema and swelling of mucosa at and above the ano-rectal junction (arrows), 4 months following chemoradiotherapy for aTI anal cancer.This has occurred at the margin of the radiation field with low signal fibrosis developing in the anal canal proper (asterisk).There is high signal in the lower sacrum due to conversion from haemopoietic to fatty bone marrow secondary to radiotherapy. A subacute radiation reaction occurs 3 to 12 months after treatment. Occasionally a chronic ano-proctitis develops.
Figure 10.17. Chronic radiation reaction.
Transaxial T2W1 showing changes in pelvic viscera 4 years following chemoradiotherapy for a T3 anal cancer.
There is a mixed signal mass (M) fixed to the left piriformis muscle (P), stable in appearance over a 1 year period—indicating the lack of residual proliferating tumour. There is a band of pre-sacral oedema (arrows). The rectum and an adjacent loop of dependent small bowel show diffuse low signal, mural thickening,and minor serosal spiculation due to fibrosis (arrowheads). Chronic radiation reactions can develop up to 5 years following treatment and persist indefinitely.
(a) Transaxial T1W1 showing recurrent tumour (arrows) with substantial destruction of the left ischiopubic ramus and pubic bone. T1W1s are useful for indicating the extent of bone disease. (b) transaxial T2W1, (c) coronal T2W1 and (d) sagittal T2W1 showing extent of soft tissue infiltration in the pelvis by recurrent disease. Tumour has invaded the prostate and bladder with fistulation to a complex deep pelvic/perineal cavity (C). There is circumferential thickening of the bladder wall (crossed arrows). A separate gas-containing cavity is present in the involved pelvic floor and obturator muscles (arrowheads). A suprapubic catheter is in situ in the bladder (SP). Note the inguinal and iliac lymph nodes (asterisk) in (b) and (c) which are equivocal for metastatic disease or hyperplasia secondary to pelvic sepsis. Multiplanar imaging is important in evaluating such complex cases and fistulae.
(a) Transaxial T2W1 and (b) coronal T2W1 showing a recurrent intermediate signal Intensity tumour mass in the left anal canal and rectum (arrows). The rest of the anal wall is thickened and of low signal intensity representing radiation induced fibrosis (arrowheads). Note probable inguinal lymph node metastasis (asterisk) and definite perirectal lymph node metastasis (solid arrowheads).
Figure 10.20. Recurrent anal cancer following chemoradiotherapy.
(a) Transaxial T2W1 and (b) coronal T2W1 showing recurrent tumour involving rectum (arrows), perirectal, right obturator and right internal iliac (asterisk) and bilateral common iliac lymph nodes (solid arrowheads). Note the dependent small bowel loop with mural thickening and mild serosal spiculation (open arrowheads) due to radiation change.
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