Peritoneal mesothelioma: the role of computed tomography in diagnosis and follow up

Peritoneal Carcinosis: What the Radiologist Needs to Know

Peritoneal carcinosis is a condition characterized by the spread of cancer cells to the peritoneum, which is the thin membrane that lines the abdominal cavity. It is a serious condition that can result from many different types of cancer, including ovarian, colon, stomach, pancreatic, and appendix cancer. The diagnosis and quantification of lesions in peritoneal carcinosis are critical in the management of patients with the condition, and imaging plays a central role in this process. Radiologists play a vital role in the multidisciplinary management of patients with peritoneal carcinosis. They need to have a thorough understanding of the pathophysiology of the condition, the underlying neoplasms, and the typical imaging findings. In addition, they need to be aware of the differential diagnoses and the advantages and disadvantages of the various imaging methods available. Imaging plays a central role in the diagnosis and quantification of lesions, and radiologists play a critical role in this process. Ultrasound, computed tomography, magnetic resonance, and PET/CT scans are used to diagnose peritoneal carcinosis. Each imaging procedure has advantages and disadvantages, and particular imaging techniques are recommended based on patient conditions. Our aim is to provide knowledge to radiologists regarding appropriate techniques, imaging findings, differential diagnoses, and treatment options. With the advent of AI in oncology, the future of precision medicine appears promising, and the interconnection between structured reporting and AI is likely to improve diagnostic accuracy and treatment outcomes for patients with peritoneal carcinosis.

Role of Computed Tomography in the Evaluation of Peritoneal Carcinomatosis

Peritoneal carcinomatosis (PC) refers to metastatic spread of tumor into the peritoneal cavity. Earlier, PC was thought to be associated with grave clinical outcome. However, various advances in treatment options including cytoreductive surgery and heated intraperitoneal chemotherapy or early post-operative chemotherapy can prolong survival of patients with peritoneal carcinomatosis. These treatment options are associated with high morbidity and mortality. The purpose of this article is to acquaint the radiologist about various appearances of peritoneal carcinomatosis in order to help clinicians in selecting candidates for surgery and avoid unnecessary potentially debilitating surgeries in patients with unresectable PC.

Peritoneal Carcinomatosis and Its Mimics: Review of CT Findings for Differential Diagnosis

Peritoneal carcinomatosis (PC) indicates the metastasis of a malignant neoplasm to the peritoneal surface. PC can be incidentally detected before discovery of the primary malignancy during an imaging study. There are other conditions that can mimic PC, such as pseudomyxoma peritonei, peritoneal lymphomatosis, peritoneal malignant mesothelioma, leiomyomatosis peritonealis disseminata, and tuberculous peritonitis. These diseases may appear similar on computed tomography (CT), but there are some clues for the differential diagnosis. This article will describe the CT findings of PC and its mimics for the differential diagnosis.

Computed Tomographic Characterization of Malignant Peritoneal Mesothelioma

Aims and Background

Peritoneal mesothelioma is a rare disease with a universally fatal outcome when managed in a traditional palliative manner. New approaches to treatment using cytoreductive surgery and intraperitoneal chemotherapy suggest that long-term survival is possible in selected patients. Early recognition of this disease process with an orderly surgical approach will begin to optimize treatment.

Methods

Thirty-three patients with malignant peritoneal mesothelioma had CT scans available for review. A Z-score was used to evaluate the incidence of cancer at a particular anatomic site as compared to a general incidence of disease at all sites. CT was analyzed by abdominopelvic anatomic sites (16), abdominopelvic regions (9), and for presence versus absence of disease in the chest. Interpretative CT findings (class 0-III) were determined for these 33 patients.

Results

Eight of 33 patients had pleural abnormalities. In an analysis of 16 abdominopelvic anatomic sites, the vesical or rectal uterine pouch was involved in 97% and the greater omentum in 91%. These anatomic sites were the only ones with a positive Z-score of >1. In the analysis of 9 abdominopelvic regions, the central and pelvic regions had Z-scores >2 for large volume disease >5 cm. For CT interpretative findings class I, class II and class III was determined in approximately one-third in each category. Sixty-six percent of the patients had ascites by CT.

Conclusions

Malignant peritoneal mesothelioma by CT evaluation predominates in tumor mass within the central and pelvic portions of the abdomen. Minimal, moderate, and extensive small bowel enlargements were seen in roughly one-third of the patients. With the use of the Z-score and interpretative small bowel findings a radiologic characterization of this disease for primary radiologic diagnosis is possible.

CT differentiation of diffuse malignant peritoneal mesothelioma and peritoneal carcinomatosis

BACKGROUND AND AIM

Diffuse malignant peritoneal mesothelioma (DMPM) and peritoneal carcinomatosis (PC) have similar imaging in computer tomography (CT). We aimed to distinguish them.

METHODS

Computer tomography findings were evaluated in 48 DMPM and 47 PC for the peritoneal, mesenteric, omentum, lymph nodes, viscera infiltration, ascites and pleural plaques.

RESULTS

Two groups had no difference in terms of thickness, clinical manifestation, diameter of lymph nodes, ascites, and viscera infiltration. But they showed differences in the following: Ratio of asbestos exposure in DMPM group was higher. Smooth and irregular peritoneal thickening were more seen in DMPM group; peritoneal nodules were more commonly detected in PC group. Forty-eight cases of peritoneum in DMPM showed mild enhanced, while 14 patients in PC showed severe enhanced. Nodular type of omentum was more common in PC group than in DMPM group; omental cake was more commonly detected in DMPM group. Mesentery involvement was more commonly seen in DMPM group. Location of enlarged lymph nodes in cardiophrenic region was more frequently identified in DMPM, whereas location of enlarged lymph nodes in retroperitoneal region was more frequently identified in PC. Lymph nodes fusion was more frequently visualized in PC. Fixation of the intestinal wall was more common in DMPM. Pleural plaque was more common in DMPM. PC had distant metastasis except primary foci and peritoneum. In PC, tumor origins were ovary in 10, digestive system in 21, breast in one.

CONCLUSION

Using a combination of CT findings may increase our ability to distinguish PC from DMPM.

Primary and secondary disease of the peritoneum and mesentery: review of anatomy and imaging features

The largest and most complex serosal membrane in the body, the peritoneum, lines the abdominal cavity, and the abdominopelvic viscera. It is frequently involved in a variety of benign and malignant processes. While secondary involvement of the peritoneum is more common, primary tumors can be a diagnostic challenge. Knowledge of the anatomy is crucial in understanding the various pathologic processes. Cross-sectional imaging plays an important role in diagnosing and evaluating the extent of the disease processes. This article reviews the imaging anatomy of the peritoneum and mesentery and the common pathologies involving it.

CT, MRI and PET imaging in peritoneal malignancy

Imaging plays a vital role in the evaluation of patients with suspected or proven peritoneal malignancy. Nevertheless, despite significant advances in imaging technology and protocols, assessment of peritoneal pathology remains challenging. The combination of complex peritoneal anatomy, an extensive surface area that may host tumour deposits and the considerable overlap of imaging appearances of various peritoneal diseases often makes interpretation difficult. Contrast-enhanced multidetector computed tomography (MDCT) remains the most versatile tool in the imaging of peritoneal malignancy. However, conventional and emerging magnetic resonance imaging (MRI) and positron emission tomography (PET)/CT techniques offer significant advantages over MDCT in detection and surveillance. This article reviews established and new techniques in CT, MRI and PET imaging in both primary and secondary peritoneal malignancies and provides an overview of peritoneal anatomy, function and modes of disease dissemination with illustration of common sites and imaging features of peritoneal malignancy.

Malignant peritoneal mesothelioma

Malignant mesothelioma is a highly aggressive neoplasm. The incidence of malignant mesothelioma is increasing worldwide. Diffuse malignant peritoneal mesothelioma (DMPM) represents one-fourth of all mesotheliomas. Association of asbestos exposure with DMPM has been observed, especially in males. The great majority of patients present with abdominal pain and distension, caused by accumulation of tumors and ascitic fluid. In the past, DMPM was considered a pre-terminal condition; therefore attracted little attention. Patients invariably died from their disease within a year. Recently, several prospective trials have demonstrated a median survival of 40 to 90 mo and 5-year survival of 30% to 60% after combined treatment using cytoreductive surgery and perioperative intraperitoneal chemotherapy. This remarkable improvement in survival has prompted new search into the medical science related to DMPM, a disease previously ignored as uninteresting. This review article focuses on the key advances in the epidemiology, diagnosis, staging, treatments and prognosis of DMPM that have occurred in the past decade.

Neoplastic and nonneoplastic conditions of serosal membrane origin: CT findings

Computed tomography (CT) is an important imaging modality for diagnosis and follow-up of neoplastic or nonneoplastic conditions of the serosal membrane. The characteristic CT findings of malignant pleural mesothelioma include unilateral pleural effusion, thickening of the mediastinal pleura, and circumferential and nodular pleural thickening of greater than 1 cm. Malignant peritoneal mesothelioma manifests as a large mass or diffuse peritoneal thickening without a definable mass and is difficult to differentiate from peritoneal carcinomatosis or tuberculosis. The imaging features of primary serous papillary carcinoma of the peritoneum resemble those of peritoneal carcinomatosis; however, the ovary is usually of normal size. The possibility of desmoplastic small round cell tumor should be considered in children or young adults with multiple peritoneal masses and no identifiable primary malignancy. The CT findings of secondary tumors include a variable amount of fluid in the serosal cavity, thickening of the serosal lining (irregular and nodular), and serosal implants. Nonneoplastic conditions manifest as focal or diffuse thickening of the serosal membrane, a variable amount of fluid in the serosal cavity, and a soft-tissue mass at CT. Although the CT findings of some of the conditions overlap, knowledge of the typical findings is helpful in narrowing the differential diagnosis.

From the archives of the AFIP: primary peritoneal tumors: imaging features with pathologic correlation

Primary peritoneal tumors are uncommon lesions that arise from the mesothelial or submesothelial layers of the peritoneum. Primary malignant mesothelioma, multicystic mesothelioma, primary peritoneal serous carcinoma, leiomyomatosis peritonealis disseminata, and desmoplastic small round cell tumor are the most prominent of these rare lesions. Primary malignant mesothelioma is a highly aggressive malignancy that occurs most commonly in older men and that has a strong association with high levels of asbestos exposure. It manifests most often as diffuse sheetlike or nodular thickening of the peritoneal surfaces, but it may occasionally be a localized mass. Multicystic mesothelioma occurs most frequently in women and has benign or indolent biologic behavior in the majority of patients. It is a multilocular cystic mass that arises from the pelvic peritoneal surfaces. Primary peritoneal serous carcinoma occurs almost exclusively in women. It is histologically identical to ovarian serous carcinoma and may be indistinguishable from metastatic ovarian carcinoma at imaging studies. Leiomyomatosis peritonealis disseminata is a rare, benign proliferative process that also occurs exclusively in women and is characterized by multiple smooth muscle nodules throughout the peritoneum. Desmoplastic small round cell tumor is a highly aggressive malignancy of unknown origin that occurs most often in the peritoneal cavity of young men. This unusual group of tumors is linked together by a common site of origin and imaging manifestations that mimic those of peritoneal carcinomatosis. Knowledge of the spectrum of imaging findings in this group of primary peritoneal tumors, along with their clinical and pathologic characteristics, is important in the evaluation of patients with diffuse peritoneal disease.

Prognostic indicators for patients undergoing cytoreductive surgery and perioperative intraperitoneal chemotherapy for diffuse malignant peritoneal mesothelioma

BACKGROUND

This study evaluates clinical, radiological and histopathological prognostic indicators for survival of patients undergoing cytoreductive surgery and perioperative intraperitoneal chemotherapy for diffuse malignant peritoneal mesothelioma (DMPM).

METHODS

Sixty-two consecutive patients with DMPM underwent cytoreduction and perioperative intraperitoneal chemotherapy at the Washington Cancer Institute. Twenty-six clinical, radiological and histopathological parameters were analyzed in univariate and multivariate analyses using overall survival as an endpoint.

RESULTS

The overall survival was 79 months (range 1-143 months), with 1-, 3- and 5-year survival rates of 84%, 58% and 50%, respectively. The following 14 prognostic variables were significant for survival in the univariate analysis: gender (P = .045), peritoneal cancer index (P = .038), completeness of cytoreduction score (P = .010), interpretive CT findings of the small bowel and mesentery (P = .001), mesothelioma cell type (P < .001), mesothelioma nuclear size (P < .001), nuclear/cytoplasmic ratio (P < .001), mitotic count (P < .001), atypical mitosis (P < .001), chromatin pattern (P < .001), cellular necrosis (P < .001), perineural invasion (P = .037), stroma pattern (P < .001) and depth of invasion (P = .014). In the multivariate analysis, the only factor that was independently associated with an improved survival after cytoreduction and perioperative intraperitoneal chemotherapy was mesothelioma nuclear size.

CONCLUSIONS

Mesothelioma nuclear size was the dominant factor determining overall survival in patients with DMPM. A histopathological staging system based on measurement of the nuclear size was proposed.

Intra-abdominal desmoplastic small round cell tumors: CT findings and clinicopathological correlations in 13 cases

PURPOSE

We report computed tomography (CT) findings in 13 patients with a primary abdominal desmoplastic small round cell tumor.

MATERIALS AND METHODS

13 cases (12 men, 1 woman, mean age=24.8 years) were found in our hospital database between 1991 and 2003. Clinical, CT and histopathological features were studied retrospectively.

RESULTS

Peritoneal involvement was the most common feature. In 10 cases, several lobulated peritoneal soft tissue masses (with a mean of four masses per patient) were seen. Two patients had diffused irregular peritoneal carcinomatosis without any distinct peritoneal masses. One patient had a solitary mass in the pelvic space. The main sites of peritoneal involvement were the pelvic space (n=7), omentum (n=5), retroperitoneal space (n=4), small bowel mesentery (n=3), paracolic gutter (n=2 on the right and n=1 on the left), transverse colon mesentery (n=1), peri-splenic space (n=1), peri-hepatic space (n=1). The soft tissue masses were often bulky (mean 6cm, range 1-28cm), lobulated and heterogeneous with hypodense areas (in 73% of cases). In six cases, moderate ascites was seen. In one case of pelvic involvement, unilateral hydronephrosis was seen. Adenopathies were present in seven cases at the time of the diagnosis (at intraperitoneal, retroperitoneal and pelvic sites in six patients and in the groin in one patient). Five patients had liver metastases (four lesions per case excepted one patient with 30 metastases). Associated thoracic metastases were seen in three patients. The diagnosis was confirmed with four CT-guided percutaneous biopsies.

CONCLUSION

Although CT features are nonspecific, the diagnosis of desmoplastic small round cell tumor may be suspected in young men with multiple bulky heterogeneous peritoneal soft tissue masses. Imaging is useful for staging and also to guide biopsies.

Computed tomography manifestations of peritoneal diseases

The peritoneal cavity is a potential space that is divided by the peritoneal reflections into various complex subspaces. It can be involved in many disease processes including developmental, inflammatory, neoplastic and traumatic conditions. Computed tomography is highly sensitive and consistent in detecting peritoneal pathology. This pictorial essay aims to emphasize and illustrate the CT features of the spectrum of peritoneal diseases.

Abdominal computed tomography scans in the selection of patients with malignant peritoneal mesothelioma for comprehensive treatment with cytoreductive surgery and perioperative intraperitoneal chemotherapy

BACKGROUND

Malignant peritoneal mesothelioma is a rare and fatal disease. Until recently, the treatment options were very limited and ineffective. The new comprehensive approach of cytoreductive surgery with perioperative intraperitoneal chemotherapy offers improved survival rates at a cost of considerable morbidity and mortality as in other peritoneal surface malignancies. The outcome after these treatments is predominantly dependent on adequate cytoreduction. The aim of the current study was to identify computed tomography (CT) scan images that are useful in patient selection for this comprehensive approach.

METHODS

An analysis of the preoperative CT scans of 30 patients with peritoneal mesothelioma treated with cytoreductive surgery and perioperative intraperitoneal chemotherapy at a single institution was performed. Based on the size of residual tumor nodules after cytoreductive surgery, patients were divided into 2 groups: those with residual lesions<or=2.5 cm (adequate cytoreduction) and those with residual lesions>2.5 cm (suboptimal cytoreduction). The CT scans for each patient were evaluated by a standardized scoring system with the reader blinded to the operative findings. Thirty-nine CT scan parameters were obtained and statistically analyzed to determine their association with the study outcome variables, namely, adequacy of cytoreduction.

RESULTS

Seven patients (64%) in the suboptimal cytoreduction group and 2 patients (11%) in the adequate cytoreduction group had a >5-cm tumor mass in the epigastric region (P=0.004). Nine patients (82%) in the suboptimal group and 2 patients (11%) in the adequate cytoreduction group had CT scans that showed loss of normal architecture of the small bowel and its mesentery (P<0.001). In a composite analysis of these 2 radiologic features, none of the patients with a >5-cm tumor mass in the epigastric region and loss of normal architecture of the small bowel and its mesentery had an adequate cytoreduction. Patients who lacked these two preoperative CT scan findings had a 94% probability of an adequate cytoreduction.

CONCLUSIONS

CT scans effectively identified large peritoneal mesothelioma tumors at crucial anatomic sites. Because adequate cytoreduction is necessary to achieve prolonged survival, CT scans became an accurate prognostic radiologic test for patient selection for comprehensive treatment.

Le péritoine acteur de la pathologie abdominale

The peritoneum is an important actor in diseases of the abdomen: defects of the peritoneum or mesos may lead to internal hernias; developmental anomalies of the peritoneum may lead to volvulus and bowel obstruction; diffuse or localized primary or secondary tumors of the peritoneum may develop; infectious, inflammatory or ischemic primary diseases of the peritoneum may cause abdominal pain, sepsis or result in the formation of fluid collections. The purpose of this presentation is to illustrate the role of imaging in the diagnosis of these different diseases and to provide some guidelines allowing their detection and characterization.

Current controversies regarding the role of asbestos exposure in the causation of malignant mesothelioma: the need for an evidence-based approach to develop medicolegal guidelines

Asbestos is a group of fibrous silicate minerals that includes two mineralogic groups: amphiboles and serpentines. While the carcinogenic role of amphiboles (eg, crocidolite and amosite) is well established, medical "experts" that tend to strongly advocate their views currently argue in medicolegal cases multiple specific issues regarding the carcinogenicity of asbestos fibers. For example, it is controversial whether chrysotile causes malignant mesothelioma (MM); what are the specific carcinogenic thresholds for amphiboles and chrysotile; what occupations are truly at risk to develop MM as a result of asbestos exposure; what is the role of chrysotile in the development of peritoneal MM; how to assign causation in individuals exposed to multiple industrial products containing variable concentrations of various asbestos fibers; and, what criteria should be used to accept causation in household exposure cases and others. The causation criteria currently acceptable in U.S. courts are surprisingly flexible and subject to variable interpretation by medical "experts." At a time where thousands of individuals are claiming causation of MM by asbestos exposure, there is a need to develop more specific causation guidelines based on scientific evidence. Evidence-based medicine has been proposed as a new approach to the study, teaching, and the practice of medicine and has been used as a process of systematically reviewing the relevant studies in the literature to assess their scientific validity and development of guidelines. This article summarizes some of the current controversies regarding the role of asbestos exposure in the causation of MM and suggests the need for future evidence-based medicine-type studies to develop causation guidelines that could be used consistently during litigation.

US of the peritoneum

Familiarity with the pathophysiology of peritoneal disease is the basis of successful ultrasound (US) study of the peritoneum. The pouch of Douglas, diaphragmatic surfaces, the paracolic gutters, and the regions of the mesentery and omentum should receive careful scrutiny in the patient at risk for a peritoneal disease process. An optimal US technique requires assessment of the entire peritoneum with a transducer selected to reflect the depth of the region of interest. US may demonstrate minute quantities of free intraperitoneal fluid and is therefore capable of providing sensitive quantitative information about ascites. Qualitative information may also be inferred, as blood, pus, and neoplastic cells demonstrate correlation with particulate ascites on gray-scale US scans. Peritoneal nodules, plaques, and thickening may be detected on the visceral or parietal peritoneal surfaces, especially when high-frequency probes are used. Transvaginal study in women increases the sensitivity of US for detection of peritoneal disease. In women who have unexplained sepsis or are at risk for carcinomatosis, transvaginal scanning should routinely be added to the regular abdominal and pelvic studies regardless of the findings of those studies. Peritoneal carcinomatosis, primary peritoneal neoplasms, pseudomyxoma peritonei, and peritonitis have characteristic appearances at US.

Mesenteric neoplasms: CT appearances of primary and secondary tumors and differential diagnosis

Computed tomography (CT) remains the optimal imaging modality for diagnosing tumors in the mesentery. Although primary neoplasms arising from the mesenchymal tissues of the mesentery are rare, the small bowel mesentery is a major avenue for the dissemination of tumor within the peritoneal cavity. Tumors spread to the mesentery by four major routes: (a) direct extension, commonly seen with carcinoid tumor of the small intestine as well as intraabdominal cancers such as pancreatic and colon cancer; (b) lymphatic dissemination of lymphoma and some epithelial malignancies; (c) hematogenic spread resulting in embolic metastases to the small intestinal wall, usually seen in melanoma and breast cancer; and (d) seeding through the peritoneum from ovarian and gastrointestinal malignancies as well as some lymphomas. Although percutaneous imaging-guided or surgical biopsy is often necessary to guide management, analysis of CT features along with the clinical history may be useful in differentiating mesenteric tumors from infectious, inflammatory, or vascular processes affecting the mesentery. The article presents the characteristic appearances of primary and secondary mesenteric neoplasms at CT and offers a rational approach to the differential diagnosis of mesenteric masses depicted at CT.

Peritoneal mesothelioma: CT and MRI findings

Two patients with histologically proven diagnosis of peritoneal mesothelioma are presented. Both patients had CT scans of the abdomen. The second patient was also examined with MRI.

CT appearance of primary papillary serous carcinoma of the peritoneum

OBJECTIVE

Our objective was to describe the CT characteristics of primary papillary serous carcinoma of the peritoneum.

CONCLUSION

The presence of peritoneal masses, extensive omental calcification, and the absence of an ovarian mass on CT--particularly in postmenopausal women--is highly suggestive of primary papillary serous carcinoma of the peritoneum and should alert the radiologist to the possibility of this diagnosis.

Malignant peritoneal mesothelioma: marked variability of CT findings

Three pathologically proven cases of malignant peritoneal mesothelioma (MPM) are shown with markedly different computed tomographic (CT) appearances. The first presented as a large enhancing pancreatic mass, a second with diffuse solid large intraperitoneal masses enveloping bowel and mesentery, and a third with predominance of ascites and small peritoneal nodules. In only one patient was there a history of possible asbestos exposure. The CT findings, pathology, and differential diagnosis of MPM are discussed.