Malignant transformation of rectal endometriosis: Preoperative diagnosis by endorectal ultrasound guided biopsy

The prevalence of malignant transformation of endometriotic lesions is estimated between 0.3% and 1%. Malignant transformations of endometriosis occur in the colorectum is rarer, accounting for 0.25%. Because the malignant transformation of colorectal endometriosis rarely involves mucosa, it is difficult to obtain abnormal tissue by routine endoscopic biopsy. In this case, we evaluated a patient with a rectal mass by endorectal ultrasound (ERUS) and performed endorectal ultrasound-guided biopsy (EGB). Malignant transformations of endometriosis were confirmed by histological result. For patients with rectal tumors but with negative findings on colonoscopy and biopsy, ERUS and EGB contribute to preoperative diagnosis.

Automated summary

Malignant transformations of endometriosis, especially in the colorectum, are rare. Routine endoscopic biopsy is not effective in diagnosing the malignant transformation of colorectal endometriosis. Endorectal ultrasound (ERUS) and endorectal ultrasound-guided biopsy (EGB) are valuable methods for diagnosing rectal tumor patients with negative findings on colonoscopy and biopsy.