a 66-year - old man with rectal cancer was found to have an incidental 3.1    2.4  cm ring - like lesion in the left rectovesical pouch on staging scans .
he subsequently underwent a laparoscopic anterior resection and a free - floating white mass was found in the left rectovesical pouch ( fig.1 ) .
histology revealed necrotic adipose tissue with focal calcification , surrounded by a thick dense fibrous capsule with no evidence of malignancy , confirming an encapsulated fat necrosis . left : mri t2w pelvic image showing ring - like lesion with a thick hypointense wall and a central fatty focus ( arrow ) .
intraperitoneal encapsulated fat necroses are postulated to be a result of infarcted epiploic appendages , with inflammatory cellular response inducing a fibrous reaction forming a capsule , resulting in a free - floating lesion .
 key clinical messagea 66-year - old man with rectal cancer was found to have an incidental ring - like lesion in the left rectovesical pouch . 
 histology revealed an encapsulated fat necrosis . 
 intraperitoneal encapsulated fat necroses are postulated to be a result of infarcted epiploic appendages resulting in a free - floating lesion . 
Intraperitoneal Encapsulated Fat Necrosis
What is the Diagnosis?
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