Peritumoral tissue reaction at transrectal US as a possible cause of overstaging in rectal cancer: histopathologic correlation.

PURPOSE

To assess if peritumoral tissue reaction (PTR) can be differentiated from tumor with transrectal ultrasound (TRUS) to avert overstaging.

MATERIALS AND METHODS

Preoperative TRUS results in 40 consecutive patients with biopsy-proved rectal cancer were compared with histopathologic reports on the specimens (study 1). To test the hypothesis that areas more anechoic than the tumor were deemed responsible for incorrect staging in study 1, a prospective study was undertaken in another 40 consecutive patients (study 2). The thickest part of PTR was measured, and results were compared with the histopathologic findings.

RESULTS

In study 1, 28 (70%) of 40 rectal cancers were staged correctly with TRUS. PTR was responsible for the misinterpretation in six of seven overstaged cases. In study 2, 38 (95%) of 40 cancers were staged correctly, and the presence or absence of PTR was described in 39 cases (98%). A statistically significant positive correlation was noted between histopathologic classification of PTR and its thickness measured with TRUS (P = .0001).

CONCLUSION

Because of its more anechoic appearance, PTR may be differentiated from the tumor by means of TRUS. This may lead to a statistically significantly higher accuracy of TRUS in the staging of rectal cancer due to the avoidance of overstaging.