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Small bowel (small intestine)

Benign tumors and tumor-like conditions

Benign cystic mesothelioma

Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 19 December 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.


● Also called multicystic mesothelioma
● Rare tumor NOT associated with asbestos, occurs most frequently in women of reproductive age, difficult to diagnose preoperatively (J Med Case Reports 2010;4:385)

Clinical features

● Often associated with prior pelvic surgery, endometriosis or pelvic inflammatory disease (J Obstet Gynaecol Res 2011;37:1126)
● Some cases may be neoplastic, others may be caused by inflammation and adhesions (Int J Gynecol Pathol 2011;30:163).
● Complete surgical resection recommended; follow up is necessary, because 50% of tumors recur after excision

Case reports

● 36 year old woman with multiple small cystic lesions in small bowel mesentery and pelvic peritoneum (Case of the Week #205)

Gross description

● Usually large, may be multifocal or unilocular; free floating cysts may also occur

Gross images

23 year old woman: multiple adherent cysts

Micro description

● Cysts are thin-walled, may contain eosinophilic fluid
● Mesothelial cells lining the cysts vary from flattened to endothelial-like to cuboidal
● Inflammatory cells are often present within stroma between cysts
● Foci of mesothelial hyperplasia may be present

Micro images


Various images from Case of Week #205

23 year old woman

72 year old woman

Left: CD31, Right: MNF-116

Positive stains

● Mesothelial cells lining cyst are keratin+, calretinin+ (Hum Pathol 2003;34:369).

Differential diagnosis

Ascitis, loculated: usually has irregular borders, is surrounded by bowel loops or abdominal / pelvic organs
Cystic teratoma: usually contains adipose and calcifications
Lymphangioma: younger patients, may contain chylous fluid grossly, often lymphoid aggregates and smooth muscle within walls, D2-40+
Other mesenteric / omental cysts / pseudocysts: usually unilocular, no distinct cyst wall or internal septa, keratin-, calretinin-
Pseudomyxoma peritonei (mucinous peritoneal metastasis): may have coexisting omental caking, soft-tissue peritoneal nodules, and scalloping of the serosal margins of the liver or spleen

End of Small bowel (small intestine) > Benign tumors and tumor-like conditions > Benign cystic mesothelioma

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