Editing Peritoneal malignancy (section)

== Pseudomyxoma peritonei ==

* Epidemiology
** Rare
** Usually 40-50yo
* Pathophysiology
** Characterised by mucinous ascites and peritoneal implants - typically most prominent in the pelvis, paracolic gutters, omentum, and subdiaphragmatic spaces
** Most common primary tumour is a perforated mucinous tumour of appendix, but can come from mucinous ovarian, colonic or pancreatic tumours
* Presentation
** Usually asymptomatic until late in disease course
** Often slow global deterioration in health
** Check for new hernia, ascites, abdominal distension with non-shifting dullness, and sometimes a palpable mass
* Grading - WHO
** Acellular mucin
** Low-grade mucinous carcinoma peritonei - low cellularity
** High-grade mucinous carcinoma peritonei - high cellularity, infiltrative invasion
** High-grade mucinous carcinoma peritonei with signed ring cells - signed ring cells
* Imaging
** Ct may show ascites, loculated pools of fluid, peritoneal-based tumour nodules, thickened omentum, scalloping of liver margins, and evidence of invasion of the mesentery, porta hepatis and small bowel
** 'Redistribution phenomenon' - peripheral location of the tumour, and relative sparing of the central small bowel and mesentery
* Management (see separate topic with technical description under 'oncology')
** Cytoreduction (resection of as much of the tumour as possible)
*** Often limited by diffuse small bowel involvement or porta hepatis involvement
*** Could include omentectomy, stripping of involved parietal peritoneum, resection of involved organs, and appendicectomy or ileocolectomy - leave no visible disease, or at least no nodules >2mm
** HIPEC (hyperthermic intra-peritoneal chemotherapy)
*** Commonly mitomycin C or oxaliplatin
* Prognosis
** A low-grade tumour with successful cytoreduction and HIPEC has a 5-year survival rate of 60-90%
** Even patients with high-grade tumours can have 5-year survival rates of 50%