Deep rectosigmoid endometriosis: "mushroom cap" sign on T2-weighted MR imaging.
OBJECTIVE
The purpose of this study is to evaluate the "mushroom cap" sign on T2-weighted MR imaging in patients with submucosal tumors in the rectosigmoid colon.


METHODS
From January 2001 to August 2009, 12 patients with four different diseases presenting or mimicking submucosal tumors in the rectosigmoid colon underwent colonic resection. All patients with deep endometriosis (n = 6), gastrointestinal stromal tumor (n = 4), metastasis from ovary cancer (n = 1), and carcinoid tumor (n = 1) had either an MRI of the rectum or pelvis before surgery. We evaluated the MRI findings and compared them with the macroscopic and microscopic observations in the resected specimens.


RESULTS
In all six cases of deep endometriosis, a characteristic "mushroom cap" shaped appearance was found on T2-weighted MR imaging. Heterogeneous low signal intensity of the hypertrophic muscularis propria, covered with high signal intensity of the mucosa and submucosa on T2-weighted MR images, looked like a "mushroom cap" with the pattern of intraluminal endophytic growth. In histological findings, deep endometriosis involved the submucosa (n = 4) or mucosa (n = 2). The "mushroom cap" sign was not present in any of the six other tumors.


CONCLUSIONS
The "mushroom cap" sign on T2-weighted MR imaging may be a characteristic sign for diagnosing deep rectosigmoid endometriosis.
Yoon
Jung Hwan
JH
Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Kangnam-Ku, Seoul, Korea.
Choi
Dongil
D
Jang
Kee-Taek
KT
Kim
Chan Kyo
CK
Kim
Heejung
H
Lee
Soon Jin
SJ
Chun
Ho-Kyung
HK
Lee
Woo Yong
WY
Yun
Seong Hyeon
SH
D000328:Adult; D012809:Colon, Sigmoid / Q000473:pathology* / Q000601:surgery; D003937:Diagnosis, Differential; D004715:Endometriosis / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D012007:Rectum / Q000473:pathology* / Q000601:surgery