Cartilaginous differentiation in peritoneal tissues: a report of two cases and a review of the literature.

Two cases of cartilaginous differentiation of the peritoneum not associated with an intraabdominal malignancy are described. This is the first detailed report of cartilaginous metaplasia of the peritoneum. The patients were female, ages 53 (Patient 1) and 77 years (Patient 2). Prior medical histories were significant for a culdotomy (to drain pelvic abscesses associated with pelvic inflammatory disease) in Patient 1 and for an open abdominal surgery in Patient 2. The peritoneal lesions were incidental findings in both cases. In Patient 1, surgery was performed for a septated ovarian cyst; the other patient underwent surgery to relieve obstructive bowel symptoms. In Patient 1, multiple firm, white lesions ranging from 2.0 to 7.0 mm were present on the serosal surfaces and the mesenteries of the small and large bowel. In Patient 2, a single firm, white lesion measuring 2 cm in maximum dimension was removed from the mesentery of the ileum. Microscopically, the lesions consisted of small nodules of mature hyaline cartilage surrounded by nondescript fibrous tissue and covered by mesothelium. There was no foreign body giant cell reaction, inflammation, or other reactive changes in the surrounding adipose tissue. These may represent metaplastic lesions of the secondary mullerian system, or a unique peritoneal response to previous surgical manipulation. Alternatively, these may represent benign neoplastic lesions (chondroma) of the submesothelium.