(appendix) Pseudomyxoma peritonei of a mature ovarian teratoma caused by MMR deficiency -Lynch syndrome

 Pseudomyxoma peritonei is a very rare type of cancer that usually begins in your appendix as a small growth, called a polyp. Or, more rarely, it can start in other parts of the bowel, the ovary or bladder. This polyp eventually spreads through the wall of your appendix or wherever else it starts.
               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
open access

Case Report

Background: Pseudomyxoma peritonei (PMP) is a rare disease with an estimated incidence of 1–2 cases per million individuals per year. PMP is characterized by the accumulation of abundant mucinous or gelatinous fluid derived from disseminated tumorous cells. Most of the tumorous cells are originated from rupture of appendiceal neoplasms, but some are from the metastasis of cancer of the colon, ovary, fallopian tube, urachus, colorectum, gallbladder, stomach, pancreas, lung and breast. Although frequent mutations in KRAS and/or GNAS genes have been reported, precise molecular mechanism underlying PMP remains to be elucidated. It is of note that mucinous tumour is one of the frequent histological features of colorectal cancer (CRC) in Lynch syndrome (LS), an autosomal dominantly
inherited disease caused by a germline mutation of the DNA mismatch repair (MMR) genes including (MLH1), (MSH2), (MSH6), and postmeiotic segregation
increased 2 (PMS2). Therefore, typical LS-associated tumours show mismatch repair instability. Although LS patients are most strongly predisposed to CRC, PMPs from mucinous CRC have not been reported in LS patients.....

In conclusion, mismatch repair defect may cause PMP through the development of ovarian tumour, one of the extra-colorectal tumours associated with Lynch syndrome. Further studies will clarify the molecular mechanisms underlying PMP originating from ovarian teratoma.