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      Drugs & Diseases > Oncology

      Peritoneal Cancer Workup

      Updated: Feb 05, 2021
      • Author: Wissam Bleibel, MD; Chief Editor: N Joseph Espat, MD, MS, FACS  more...
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      Workup

      Laboratory Studies

      In malignant peritoneal mesothelioma, findings from cytologic examination of ascites can suggest the diagnosis, and findings from percutaneous biopsy of the omentum can help verify the diagnosis. This condition is usually confined to the abdomen at the time of diagnosis.

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      Imaging Studies

      Standard imaging tests, including ultrasonography and helical computed tomography (CT) scans, are notably insensitive for the detection of peritoneal tumors. CT is limited in detecting small peritoneal metastases. CT can depict tumors larger than 1 cm with sensitivity of 85–93% and specificity of 91–96%, but the sensitivity decreases to 25–50% in detecting implants that are 1 cm or smaller. [19]

      Ultrasonography is similarly insensitive; rather than relying on solid tumor detection, therefore, it is important to consider findings that may suggest the presence of peritoneal lesions. These include the presence of ascites, fixing together of bowel loops, thickening of mesentery, and omental matting.

      CT scan findings are nonspecific in primary papillary serous carcinoma of the peritoneum. Consider this diagnosis when findings include the following:

      • Ascites
      • Omental caking
      • Diffuse enhancement with nodular thickening of the parietal peritoneum of the pelvis
      • Normal-sized ovaries, with or without a fine enhancing surface nodularity of the ovary.

      Malignant peritoneal mesotheliomas produce CT findings that range from peritoneum-based masses (a so-called "dry" appearance) to ascites, irregular or nodular peritoneal thickening, and an omental mass (a so-called "wet" appearance). Scalloping of the peritoneum or direct invasion of adjacent abdominal organs may also be seen. [1]

      Some studies show that magnetic resonance imaging (MRI) is superior to helical CT scan for the detection of peritoneal and bowel wall abnormalities.

      Preoperative imaging of the abdomen and pelvis plays an important role in determining the extent of peritoneal disease in patients who are being considered for cytoreductive surgery. Delayed gadolinium-enhanced imaging combined with diffusion-weighted MRI has been shown to be a superior imaging modality to predict which patients will be able to undergo complete primary cytoreductive surgery. In one study, MRI more accurately predicted peritoneal cancer index (PCI) preoperatively in patients undergoing evaluation for cytoreductive surgery than CT. PCI measures the size and extent of peritoneal tumor at laparotomy.  For predicting resectability, MRI had sensitivity of 95%, specificity of 70%, and accuracy of 88% compared with 55%, 86%, and 63%, respectively, for CT. [20]

      Positron emission tomography (PET) imaging has not been shown to be sensitive for lesions smaller than 1 cm in the abdominal cavity.

      Dual-time point imaging after carbonated water may increase the accuracy of 18F-fluorodeoxyglucose (FDG) PET/CT for the imaging of peritoneal cancer in patients affected by colorectal cancer. [21]

      Findings from radionuclide scan studies can help confirm the diagnosis of peritoneal hemangiomas; the isotope concentrates in the area where platelets are being sequestered. A CT scan and ultrasound also may detect larger hemangiomas. Angiographic evaluation is a more precise, although invasive, procedure that may be considered when radionuclide scans, CT scan, and ultrasound findings are negative.

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      Procedures

      The workup of peritoneal lesions includes peritoneal lavage cytology. Peritoneal lavage can be performed using a percutaneous closed technique or at the time of laparoscopy or laparotomy. The sensitivity of the test results depends on the ability to completely lavage all regions of the peritoneal cavity and the ability to detect cancer cells being shed into the peritoneal cavity by the tumor.

      Direct visualization of the peritoneal surfaces along with palpation of the abdominal contents is by far the most sensitive modality for detecting peritoneal cancer. This can be accomplished with a minimally invasive approach (ie, laparoscopy), which allows for safe, directed peritoneal lavage for cytology, or with open abdominal exploration and palpation of the peritoneal surfaces. Open abdominal exploration and palpation are extremely sensitive for 1- to 2-mm peritoneal nodules.

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      Histologic Findings

      Primary peritoneal carcinoma is histologically indistinguishable from primary epithelial ovarian carcinoma; however, primary ovarian cancer can be excluded when the following criteria are present:

      • Both ovaries are of normal size
      • The extraovarian involvement is greater than the involvement on the surface of the ovary
      • The ovarian component is smaller than 5 × 5 mm within the ovary or confined to the ovarian surface
      • Cytologic characteristics are of the serous type.
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