Benign cystic mesothelioma of the peritoneum in a male child.

The benign cystic mesothelioma of the peritoneum is a rare lesion that occurs predominatly in women of reproductive age and has a high propensity for local recurrence. It is very rare in childhood, especially in boys, being reported in only 4 cases. A new case of benign cystic mesothelioma of the peritoneum in an 11-year-old boy is reported. The lesion occupied the entire left abdomen, arising from the transverse mesocolon, and it was accompanied by 4 small cysts. The patient had a coexistent right-sided renal agenesis. The mesothelial nature of the cysts epithelial lining cells was confirmed by immunopositivity for calretinin, cytokeratin 5/6, HBME1, and epithelial membrane antigen (EMA). No recurrence of the lesion was noted in the 7-month follow-up. Pathologists and clinicians should be aware of the existence of this rare entity in childhood to establish an accurate diagnosis and provide close follow-up after the surgery.