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abdominal mesothelial cyst

Friday 13 January 2006

mesothelial inclusion cysts, benign cystic mesothelioma

The lesions are unifocal and multifocal.

The lesions are located on the surface of the peritoneum in the cul de sac, on the intestines, urinary bladder, uterine adnexa, also involved round ligament within the pelvis and in the inguinal canal.

Additionally, small cysts, free-floating in the peritoneal cavity can be present.

Gross appearance

- The lesions can be polycystic.
- The surgical materials range from three fragments measuring 0.5 cm each to seven fragments, with the maximum size of 14x6 cm.
- The cysts are from microscopic size to 2 cm in diameter.
- The majority are thin-walled, semitranslucent, filled with clear or yellowish fluid or gelatinous contents.
- In some cases, the cyst walls are thicker and show intense inflammatory lesions and fibrinous exudate.

Microscopy

- The majority of cysts are lined with a single layer of flattened or cuboid mesothelial cells (CK+, calretinin+).
- In some patients, the mesothelium demonstrated diffuse squamous cell metaplasia.
- Sometimes, the cells focally form small papillae and are vacuolated.
- No mucus is observed either in the cytoplasm or outside the cells.

Immunochemistry

- Immunohistochemical reactions to CEA, ER, PR and MIB-1 are negative.
- Intramural proliferations and intracystic detached clumps of cells showed both mesothelial cells (without any mitotic activity and signs of atypia) and macrophages (CD68+).

Types

- unifocal
- multifocal

Localization

- diaphragmatic mesothelial cysts
- peritoneal surface (surface of the peritoneum)

  • peritoneal cul-de-sac
  • intestines
  • urinary bladder
  • uterine adnexa
  • round ligament within the pelvis
  • inguinal canal
  • free-floating cysts in the peritoneal cavity

- visceral

  • intra-hepatic mesothelial cysts (12489001)
  • splenic mesothelial cysts

Synopsis

- Gross appearance: polycystic lesions
- Size: microscopic size to 2 cm in diameter
- thin-walled, semitranslucent, filled with clear or yellowish fluid or gelatinous contents
- cysts were with a single layer of flattened or cuboid mesothelial cells (CK+, calretinin+)
- diffuse squamous cell metaplasia
- cells focally forming small papillae
- vacuolated cells
- no mucus

Immunohistochemistry

- CK +
- calretinin +

Associations

- diaphragmatic defect (diaphragmatic hernia)

References

- Mesothelial inclusion cysts (so-called benign cystic mesothelioma)—a clinicopathological analysis of six cases. Urbańczyk K, Skotniczny K, Kuciński J, Friediger J. Pol J Pathol. 2005;56(2):81-7. PMID: 16092670

- Arber DA, Strickler JG, Weiss LM. Splenic mesothelial cysts mimicking lymphagiomas. Am J Surg Pathol. 1997 Mar;21(3):334-8. PMID: 9060604

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