Multimodality imaging of common and uncommon peritoneal diseases: a review for radiologists

High-grade B-cell lymphoma, not otherwise specified, presenting as primary peritoneal lymphomatosis and successfully treated with dose-adjusted EPOCH-R

Peritoneal lymphomatosis (PL) is a rare lymphoma-associated condition defined as the dissemination of lymphoma cells in the peritoneum. An 82-year-old man presented with abdominal pain, heartburn, and high fever. Radiological findings, including positron emission tomography-computed tomography (PET-CT), and gastrointestinal fiberscopy, showed diffuse thickening of the peritoneum, omentum, and mesentery; however, no lymphadenopathy, hepatosplenomegaly, or gastrointestinal lesions were observed. Under suspicion of peritonitis carcinomatosa of unknown origin, exploratory laparoscopy was performed that revealed multiple white nodules and masses on the surfaces of the peritoneum, mesentery, and intestinal serosa. The histopathological and cytogenetic findings of the peritoneum revealed high-grade B-cell lymphoma, not otherwise specified, and a gain of MYC by fluorescence in-situ hybridization. The patient was treated with two cycles of R-CHOP therapy, followed by six cycles of dose-adjusted EPOCH-R therapy, and a complete metabolic response was confirmed by PET-CT. Since there are no specific radiological findings to confirm the diagnosis of PL, a histopathological diagnosis is usually required. Most PL exhibit an aggressive lymphoma phenotype and can be cured by appropriate chemotherapy. Therefore, early diagnosis and treatment are desirable.

Rare Variants of Malignant Peritoneal Mesothelioma: a Literature Review

Primary peritoneal mesothelioma (PM) is a rare and aggressive malignancy that arises from the peritoneum and classified into diffuse malignant peritoneum mesothelioma (DMPM) and borderline variants, viz. multicystic peritoneal mesothelioma (MCPM) and well-differentiated papillary peritoneal mesothelioma (WDPPM). The borderline variants are rarer than conventional DMPM, are less aggressive form accounting for 3-5% of all cases of peritoneal mesothelioma. In this narrative review article, we have discussed the pathogenesis, clinical presentation, natural history, and management of these rarer variants of PM, viz. MCPM and WDPPM. Histologically, MCPM typically consists of small cysts composed of mesothelial epithelium with benign bland cuboidal cells with clear fluids; cells lack cellular atypia and have increased number of mitoses. WDPPM has specific papillary component with myxoid plump cores and single layer of bland mesothelial cells. Both the variants commonly present as incidental finding or symptoms of chronic abdominal pain, chronic pelvic inflammatory disease, pelvic mass, and infertility. In the absence of treatment, these diseases are slow growing with major concerns being that both the variants have malignant transformation capabilities and a high rate of recurrence. In the light of current evidences, it is recommended that MCPM and WDPPM patients should be offered a complete cytoreductive surgery and hyperthermic intraperitoneal chemotherapy consisting of cisplatin and doxorubicin. Collaborative multi-institutional studies are needed to generate more data and formulate robust guidelines.

Imaging in metastatic breast cancer, CT, PET/CT, MRI, WB-DWI, CCA: review and new perspectives

BACKGROUND

Breast cancer is the most frequent cancer in women and remains the second leading cause of death in Western countries. It represents a heterogeneous group of diseases with diverse tumoral behaviour, treatment responsiveness and prognosis. While major progress in diagnosis and treatment has resulted in a decline in breast cancer-related mortality, some patients will relapse and prognosis in this cohort of patients remains poor. Treatment is determined according to tumor subtype; primarily hormone receptor status and HER2 expression. Menopausal status and site of disease relapse are also important considerations in treatment protocols.

MAIN BODY

Staging and repeated evaluation of patients with metastatic breast cancer are central to the accurate assessment of disease extent at diagnosis and during treatment; guiding ongoing clinical management. Advances have been made in the diagnostic and therapeutic fields, particularly with new targeted therapies. In parallel, oncological imaging has evolved exponentially with the development of functional and anatomical imaging techniques. Consistent, reproducible and validated methods of assessing response to therapy is critical in effectively managing patients with metastatic breast cancer.

CONCLUSION

Major progress has been made in oncological imaging over the last few decades. Accurate disease assessment at diagnosis and during treatment is important in the management of metastatic breast cancer. CT (and BS if appropriate) is generally widely available, relatively cheap and sufficient in many cases. However, several additional imaging modalities are emerging and can be used as adjuncts, particularly in pregnancy or other diagnostically challenging cases. Nevertheless, no single imaging technique is without limitation. The authors have evaluated the vast array of imaging techniques - individual, combined parametric and multimodal - that are available or that are emerging in the management of metastatic breast cancer. This includes WB DW-MRI, CCA, novel PET breast cancer-epitope specific radiotracers and radiogenomics.

Differentiating peritoneal tuberculosis and peritoneal carcinomatosis based on a machine learning model with CT: a multicentre study

PURPOSE

It is still a challenge to make early differentiation of peritoneal tuberculosis (PTB) and peritoneal carcinomatosis (PC) clinically as well as on imaging and laboratory tests. We aimed to develop a model to differentiate PTB from PC based on clinical characteristics and primary CT signs.

METHODS

This retrospective study included 88 PTB patients and 90 PC patients (training cohort: 68 PTB patients and 69 PC patients from Beijing Chest Hospital; testing cohort: 20 PTB patients and 21 PC patients from Beijing Shijitan Hospital). The images were analyzed for omental thickening, peritoneal thickening and enhancement, small bowel mesentery thickening, the volume and density of ascites, and enlarged lymph nodes (LN). Meaningful clinical characteristics and primary CT signs comprised the model. ROC curve was used to validate the capability of the model in the training and testing cohorts.

RESULTS

There were significant differences in the following aspects between the two groups: (1) age; (2) fever; (3) night sweat; (4) cake-like thickening of the omentum and omental rim (OR) sign; (5) irregular thickening of the peritoneum, peritoneal nodules, and scalloping sign; (6) large ascites; and (7) calcified and ring enhancement of LN. The AUC and F1 score of the model were 0.971 and 0.923 in the training cohort and 0.914 and 0.867 in the testing cohort.

CONCLUSION

The model has the potential to distinguish PTB from PC and thus has the potential to be a diagnostic tool.

Extramedullary Hematopoiesis: A Forgotten Diagnosis and a Great Mimicker of Malignancy

ABSTRACT

Radiology errors have been reported in up to 30% of cases when patients have abnormal imaging findings. Although more than half of errors are failures to detect critical findings, over 40% of errors are when findings are recognized but the correct diagnosis or interpretation is not made. One common source of error is when imaging findings from one process simulate imaging findings from another process but the correct diagnosis is not made. This can result in additional imaging studies, unnecessary biopsies, or surgery. Extramedullary hematopoiesis is one of those uncommon disease processes that can produce many imaging findings that may lead to misdiagnosis. The objective of this article is to review the common and uncommon imaging features of extramedullary hematopoiesis while presenting a series of interesting relevant illustrative cases with emphasis on CT.

The role of imaging in diagnosis and management of malignant peritoneal mesothelioma: a systematic review

PURPOSE

Imaging of the peritoneum and related pathology is a challenge. Among peritoneal diseases, malignant peritoneal mesothelioma (MPeM) is an uncommon tumor with poor prognosis. To date, there are no specific guidelines or imaging protocols dedicated for the peritoneum and MPeM. The objective of this study was to analyze the literature describing imaging modalities used for MPeM to determine their relative clinical efficacy and review commonly reported imaging features of MPeM to promote standardized reporting.

METHODS

We performed a systematic review of original research articles discussing imaging modalities in MPeM from 1999 to 2020. Effectiveness measures and common findings were compared across imaging modalities.

RESULTS

Among 582 studies analyzed, the most-used imaging modality was CT (54.3%). In the differentiation of MPeM from peritoneal carcinomatosis, one study found CT had a diagnostic sensitivity of 53%, specificity of 100%, and accuracy of 68%. Two studies found fluorodeoxyglucose positron emission tomography (FDG-PET) had sensitivity of 86-92%, specificity of 83-89%, and accuracy of 87-89%. Another study found magnetic resonance imaging (MRI) was the best predictor of the peritoneal carcinomatosis index. Characteristics shown to best differentiate MPeM from other diseases included ascites, peritoneal thickening, mesenteric thickening, pleural plaques, maximum tumor dimension, and number of masses.

CONCLUSION

Most published MPeM imaging studies utilized CT. PET/CT or MRI appear promising, and future studies should compare effectiveness of these modalities. MPeM imaging reports should highlight ascites, number of and maximum tumor dimension, peritoneal/mesenteric thickening, and associated pleural plaques, allowing for better aggregation of MPeM imaging data across studies.

Performances of 18F-FDOPA PET/CT in the Preoperative Evaluation of the Peritoneal Cancer Index in Small Intestine Neuroendocrine Tumors

PURPOSE

Peritoneal carcinomatosis (PC) concerns up to 30% of patients with a neuroendocrine tumor (NET), especially of the small intestine. Aggressive management of carcinomatosis seems to be justified, especially with regard to possible mechanical complications. 18F-FDOPA PET/CT is known to be the most sensitive imaging modality for the detection of small bowel NET metastases, yet its performance in the detection of PC is not well studied. The main objective of our study is to evaluate the performances of preoperative 18F-FDOPA PET/CT in the prediction of surgical peritoneal cancer index.

METHODS

All patients referred to our center for an 18F-FDOPA PET/CT from October 2017 to January 2021 were retrospectively screened. Images were analyzed by a blinded nuclear medicine physician, and peritoneal abnormalities were reported to comply with the surgical peritoneal cancer index standard. Per patient analysis and per region analysis were then conducted.

RESULTS

Thirty-three patients were included; 6 patients (35 regions) presented a peritoneal carcinosis. Peritoneal Carcinomatosis Index (PCI) estimated on 18F-FDOPA PET/CT was significantly and strongly correlated to surgical PCI (r = 0.96, P < 0.001). Patient-based sensitivity, specificity, negative predictive value, and positive predictive value for 18F-FDOPA PET/CT were 100%, 93%, 100%, and 75%, respectively. The agreement between 18F-FDOPA and surgery regarding PC was excellent (Cohen κ = 0.82 on per patient analysis, 0.74 on per region analysis).

CONCLUSIONS

A preoperative estimation of PCI is achievable based on 18F-FDOPA PET/CT for small intestine NET and could allow to optimize surgical procedures and patient selection.

Peritoneal disease: key imaging findings that help in the differential diagnosis

The peritoneum is a unique serosal membrane, which can be the site of primary tumors and, more commonly, secondary pathologic processes. Peritoneal carcinomatosis is the most common malignant condition to affect the peritoneal cavity, and the radiologist plays an important role in making the diagnosis and assessing the extent of disease, especially in sites that may hinder surgery. In this review, we address the role of the radiologist in the setting of peritoneal pathology, focusing on peritoneal carcinomatosis as this is the predominant malignant process, followed by revising typical imaging findings that can guide the differential diagnosis.We review the most frequent primary and secondary peritoneal tumor and tumor-like lesions, proposing a systemic approach based on clinical history and morphological appearance, namely distinguishing predominantly cystic from solid lesions, both solitary and multiple.

Characterizing omental PET/CT findings for differentiating tuberculous peritonitis from peritoneal carcinomatosis

PURPOSE

To characterize and investigate PET/CT findings in the omentum in the differentiation of tuberculous peritonitis (TBP) and peritoneal carcinoma (PC).

METHODS

Thirty-nine patients with TBP and 113 patients with PC who underwent PET/CT were retrospectively enrolled. The omental uptake intensity, distribution characteristics, contracture, size and boundary of soft-tissue lesions, and CT patterns were reviewed.

RESULTS

Absent and focal FDG uptake in the lesser omentum was more common in the PC patients (P = 0.034 and P = 0.017, respectively), and diffuse FDG uptake in the lesser omentum was more common in the TBP patients (P < 0.001). An apron-like pattern in the greater omentum commonly occurred in the TBP patients (P = 0.004). Micronodules (< 5 mm) were more common in the TBP patients (P < 0.001), and masses (> 3 cm) were more common in the PC patients (P = 0.001). Smudged and nodular patterns occurred more frequently in the TBP patients than in the PC patients (P < 0.001 and P = 0.003, respectively), and the caked pattern occurred more frequently in the PC patients (P < 0.001). There was no significant difference in the FDG uptake intensity and the boundary of soft-tissue lesions between the TBP and PC patients (P = 0.191 and P = 0.061, respectively).

CONCLUSION

Diffuse FDG uptake, an apron-like pattern, micronodules, and a smudged and nodular pattern might be significant differential features of TBP. Absent and/or focal FDG uptake, mass, and a caked pattern might be significant differential features of PC.

Spilled stones following pyelolithotomy: An unusual mimic of peritoneal carcinomatosis

While spillage of intraperitoneal gallstones has been reported frequently in the literature, spilled renal stones after urologic intervention is rare. The dropped renal stones may mimic peritoneal carcinomatosis (PC) on imaging, causing concern and potentially leading to unnecessary diagnostic workup. Additionally, these dropped stones may cause surrounding inflammation, potentially leading to the formation of adhesions or an intra-abdominal abscess. Calcifications along the peritoneal lining are generally interpreted as peritoneal carcinomatosis until proven otherwise. However, this case highlights the importance of a detailed history and comparison with prior imaging. We describe a rare case of intraperitoneal spilled renal stones after pyelolithotomy initially mistaken for PC, in addition to a review of diagnostic pitfalls and radiologic mimics of PC.

Foliate Lymphoid Aggregates as Novel Forms of Serous Lymphocyte Entry Sites of Peritoneal B Cells and High-Grade B Cell Lymphomas

The cellular homeostasis of lymphoid tissues is determined by the continuous interactions of mobile hematopoietic cells within specialized microenvironments created by sessile stromal cells. In contrast to the lymph nodes and mucosal lymphoid tissues with well-defined entry and exit routes, the movement of leukocytes in the peritoneal cavity is largely unknown. In this study, we report that, in addition to the omental milky spots and fat-associated lymphoid clusters, in mice, the serous surface of the mesenteric adipose streaks contains lymphocyte-rich organoids comprised of a highly compacted leaf-like part connected to the adipose tissue that can also efficiently bind B cells and high-grade B cell lymphoma (diffuse large B cell lymphoma) cells. Denoted as foliate lymphoid aggregates (FLAgs), these structures show incomplete T/B segregation and a partially differentiated stromal architecture. LYVE-1-positive macrophages covering FLAgs efficiently bind i.p. injected normal B cells as well as different types of diffuse large B cell lymphoma cells. Within FLAgs, the lymphocytes compartmentalize according to their chemokine receptor pattern and subsequently migrate toward the mesenteric lymph nodes via the mesenteric lymphatic capillaries. The blood supply of FLAgs includes short vascular segments displaying peripheral lymph node addressin, and the extravasation of lymphocytes to the omental and mesenteric adipose tissues is partly mediated by L-selectin. The appearance of i.p. injected cells in mesenteric lymph nodes suggests that the mesentery-associated lymphatics may also collect leukocytes from the fat-associated lymphoid clusters and FLAgs, thus combining the mucosal and serous exit of mobile leukocytes and increasing the range of drainage sites for the peritoneal expansion of lymphoid malignancies.

FOLFIRINOX in patients with peritoneal carcinomatosis from pancreatic adenocarcinoma: a retrospective study

Background

Peritoneal carcinomatosis (pcm) in metastatic pancreatic ductal adenocarcinomas (mpdac) is frequently encountered in day-to-day practice, but rarely addressed in the literature. The objective of the present study was to describe the management and outcome of patients diagnosed with pcm.

Methods

Data for all consecutive patients with mpdac treated in our centre between 1 January 2014 and 31 August 2015 were analyzed retrospectively. Computed tomography imaging was centrally reviewed by a dedicated radiologist to determine the date of pcm diagnosis.

Results

The analysis included 48 patients. Median age in the group was 61 years, and 41 patients had an Eastern Cooperative Oncology Group performance status (ecog ps) of 0-1. All patients presented with pcm either synchronously (group 1) or metachronously (group 2). Those groups differed significantly by baseline ecog ps and neutrophil-to-lymphocyte ratio (nlr), with ecog ps being poorer and nlr being higher in group 1. In addition to pcm, the main sites of metastasis were liver (62.5%) and lungs (31.3%). First-line chemotherapy in 36 patients (75%) was folfirinox (fluorouracil-irinotecan-leucovorin-oxaliplatin). The median overall survival for the entire population was 10.81 months [95% confidence interval (ci): 7.16 months to 14.16 months]; it was 13.17 months (95% ci: 5.9 months to 15.4 months) for patients treated with folfirinox. Median overall survival was 7.13 months (95% ci: 4.24 months to 10.41 months) for patients in group 1 and 14.34 months (95% ci: 9.79 months to 19.91 months) for patients in group 2, p = 0.1296.

Conclusions

Compared with other metastatic sites, synchronous pcm seems to be a poor prognostic factor. It could be more frequently associated with a poor ecog ps and a nlr greater than 5 in this group of patients. In patients with mpdac and pcm, either synchronous or metachronous, folfirinox remains an efficient regimen.

Differentiation of peritoneal tuberculosis from peritoneal carcinomatosis by the Omental Rim sign. A new sign on contrast enhanced multidetector computed tomography

INTRODUCTION

Peritoneal TB (PTB) is the commonest presentation of abdominal TB. One of its close mimics is peritoneal carcinomatosis (PC). We present a new sign of PTB on contrast enhanced multidetector computed tomography (CT) called the Omental Rim (CT-OR) sign which helps to accurately differentiate PTB from PC.

MATERIALS AND METHODS

A prospective study was performed from 2014 to 2018 on patients referred for CT at a tertiary referral hospital. The study group consisted of consecutive 85 patients, 52 men and 33women, with PTB. The control group consisted of 168 consecutive patients, 96 men and 72 women, with PC. The images were analysed for omental thickening and enhancement, peritoneal thickening and nodules, mesenteric thickening and nodules, presence, quantity, loculation and density of ascites, presence of nodes, bowel and other organ involvement as well as a new sign called the CT-OR sign.

RESULTS

The CT-OR sign could identify 85% of patients with PTB. It was absent in 96% of patients with PC and was effective in ruling out PC (p < 0.001). The sign had a sensitivity of 85%, specificity of 96%, positive predictive value of 92%, negative predictive value of 93% and accuracy of 92%.

CONCLUSION

The new CT-OR sign is a sensitive and specific sign for PTB. It helps to rule out majority of PC.

Ultrasonographic features of colonic B-cell lymphoma with mesenteric lymphomatosis in a cat

A 10-year-old male neutered Domestic Shorthair cat was referred for chronic inappetence, weight loss, and hematochezia and an abdominal mass. Abdominal ultrasonography revealed a heterogeneously hypoechoic transmural colonic mass, which extended beyond the serosa and into the adjacent mesentery. Cytology and clonality assays of fine needle aspirates of the mass and mesenteric nodules yielded a diagnosis of B-cell lymphoma. Colonic lymphoma with mesenteric involvement can have a similar appearance to carcinomatosis, therefore a definitive diagnosis requires sampling and further testing of the mesenteric lesions.

Sonographic features of peritoneal lymphomatosis in 4 cats

Background

The metastatic spread of feline lymphoma to the peritoneum (“lymphomatosis”) has been rarely reported in the literature. The sonographic features specific to this rare disease manifestation have not been described and have important treatment and prognostic considerations prompting definitive diagnosis.

Objectives

To describe the ultrasonic features of feline peritoneal lymphomatosis.

Animals

Four cats with alimentary lymphoma and peritoneal metastasis confirmed using cytology, histology, or both.

Results

The sonographic features described include either a nonobstructive, focally diffuse, and circumferential intestinal mass, or an eccentric, focally diffuse, gastric mass. The intestinal and gastric lesions exhibited hypo‐to‐anechoic transmural wall thickening with loss of wall layering in association with discrete‐to‐coalescing plaques or sheets of thickened, hypoechoic tissue throughout the mesentery or omenta. All cases exhibited only small volumes of anechoic free peritoneal fluid. Three of the 4 cats also had multiple small hypoechoic nodular foci on the parietal and/or visceral peritoneal surfaces. Two cats had bilateral renomegaly because of lymphoma invasion (2/4) and 1 cat had local lymphadenopathy secondary to lymphoma invasion (1/4).

Conclusions and Clinical Importance

Peritoneal lymphomatosis is a rare manifestation of lymphoma metastasis and to date appears to be associated specifically with B‐cell alimentary lymphoma.

Germline BAP1-positive patients: the dilemmas of cancer surveillance and a proposed interdisciplinary consensus monitoring strategy

The germline BAP1 (BRCA1-associated protein-1) mutation and associated cancer pre-disposition syndrome was first described in 2011. Since then, physicians have considered this diagnosis for patients with a characteristic personal or family history of BAP1-associated tumours (mainly uveal and cutaneous melanoma, pleural/peritoneal mesothelioma, renal cell carcinoma and BAP1-deficient melanocytic lesions). However, a positive germline BAP1 mutation detection creates significant uncertainty in terms of appropriate cancer surveillance. A number of groups have proposed surveillance plans but important management dilemmas remain unresolved. The lifetime risk of developing cancer is not known and it is not clear if surveillance would lead to detecting cancer at an earlier stage or change survival outcomes. A consensus monitoring strategy was initially proposed at the Melanoma Institute Australia Melanoma Multidisciplinary Team meeting and later discussed with specialists in the field of cancer genetics, pathology, radiology, medical oncology, ophthalmology and dermatology. The objectives were to facilitate early diagnosis, incorporating where possible, clinically based and low/non-ionising radiation imaging modalities, applying the principles of a good screening test and a multidisciplinary focus.

Desmoplastic Small Round Blue Cell Tumor: A Review of Treatment and Potential Therapeutic Genomic Alterations

Desmoplastic small round blue cell tumors (DSRCTs) originate from a cell with multilineage potential. A molecular hallmark of DSRCT is the EWS-WT1 reciprocal translocation. Ewing sarcoma and DSRCT are treated similarly due to similar oncogene activation pathways, and DSRCT has been represented in very limited numbers in sarcoma studies. Despite aggressive therapy, median survival ranges from 17 to 25 months, and 5-year survival rates remain around 15%, with higher survival reported among those undergoing removal of at least 90% of tumor in the absence of extraperitoneal metastasis. Almost 100% of these tumors contain t(11;22) (p13;q12) translocation, and it is likely that EWS-WT1 functions as a transcription factor possibly through WT1 targets. While there is no standard protocol for this aggressive disease, treatment usually includes the neoadjuvant HD P6 regimen (high-dose cyclophosphamide, doxorubicin, and vincristine (HD-CAV) alternating with ifosfamide and etoposide (IE) chemotherapy combined with aggressively attempted R0 resection). We aimed to review the molecular characteristics of DSRCTs to explore therapeutic opportunities for this extremely rare and aggressive cancer type.

Adnexal masses associated with peritoneal involvement: diagnosis with CT and MRI

Given the unique intra-peritoneal anatomic location of the adnexa, tubo-ovarian diseases can commonly spread into the peritoneal cavity. Peritoneal seeding may occur in a spectrum of adnexal conditions including infectious diseases, endometriosis, and benign or malignant primary or secondary ovarian tumors. CT is usually the imaging modality on which the concomitant involvement of the peritoneum and the ovary is depicted. The first diagnosis to be considered by the radiologist is generally peritoneal carcinomatosis from ovarian cancer but other conditions cited above have also to be borne in mind and may be suggested on the basis of careful assessment of CT findings or on further MR findings. MRI may indeed help characterize the lesions in some cases. The purpose of this review is to describe the clinical and imaging patterns of peritoneal involvement that may be found in association with different ovarian lesions. Familiarity with these patterns and diagnoses will help the radiologist narrow the differential diagnosis and make an accurate diagnosis, thus facilitating patient management and avoiding unnecessary invasive treatment.

A Case of Well-Differentiated Papillary Mesothelioma of the Male Peritoneum: Successful Treatment by Systemic Chemotherapy

Well-differentiated papillary mesothelioma of the peritoneum (WDPMP) is a rare subtype of epithelioid mesothelioma, which is usually seen in young women without a history of asbestos exposure, and generally, has an indolent course. The relative rarity of this neoplasm in males prompted us to report this case of a well-differentiated papillary mesothelioma of the peritoneum in a 36-year-old man.

The patient, who had no history of asbestos exposure, presented with abdominal pain and ascites of unknown etiology. Computed tomography showed abundant ascites with nodules of the peritoneal cavity. Laparoscopic examination revealed a large number of white miliary nodules diffusely covering the peritoneum. Pathology revealed a diagnosis of well-differentiated papillary mesothelioma of the peritoneum, based on histomorphology and immunohistochemistry. The patient started chemotherapy with cisplatin and pemetrexed. After six cycles of chemotherapy, the effectiveness of this chemotherapy was checked by only the computed tomography. PET scan was not used because it is not routinely recommended in WDPMP. Few data are currently available in the literature regarding the performance of the PET scan in WDPMP. Nine months later, the patient was free of symptoms.

Based on reviewing the literature and our observations in this case, consultation of other pathologists is highly recommended to discern WDPMP from other disseminated peritoneal diseases, in order to offer the most effective and safe therapeutic strategy. Chemotherapy should be strongly considered if the tumor is unresectable and accompanied by symptoms. Cisplatin and pemetrexed chemotherapy could be a promising therapeutic choice.

Primary systemic amyloidosis: imaging interpretation of this complex multisystemic disease

This report highlights the diagnostic complexities involved in the case of a 63-year-old female who presented with a non-productive cough and shortness of breath on exertion. Initial chest radiograph demonstrated generalized abnormal interstitial lung markings with thickened peripheral septal lines. Further characterization was sought by CT scan of the chest, and given the possibility of lymphangitic carcinomatosis, a CT scan of the abdomen and pelvis was also performed. The CT scan findings revealed septal line thickening, abnormal omental soft tissue with calcified deposits and wall thickening of the stomach and proximal duodenum. A preliminary differential diagnosis of peritoneal carcinomatosis was made, but cancer markers were equivocal. A CT-guided biopsy of the “omental cake” was non-diagnostic, hence formal biopsy via laparoscopy was undertaken. While awaiting the results, the patient was readmitted with acute haematemesis. Gastric and duodenal biopsies from the endoscopic assessment were positive for Congo red stain and birefringent under polarizsed light, which was consistent with amyloidosis. Histology from the omental biopsies and additional haematological tests concurred. The patient was diagnosed with advanced systemic amyloid light-chain amyloidosis comprising diffuse pulmonary amyloidosis, calcified omental soft tissue deposits, and extensive soft tissue amyloid with cardiac and gastrointestinal involvement. We discuss the spectrum of differential diagnoses posed by the imaging findings and the difficulties faced in interpreting this complex case of systemic amyloidosis.

Desmoplastic small round cell tumor: postoperative retroperitoneal mass

We describe the case of a 14-year-old boy who presented with a large, 17.6-cm retroperitoneal mass, along with multiple metastases, and was diagnosed with desmoplastic small round cell tumor. After initial chemotherapy, he underwent gross total resection with a positive margin. On postoperative radiation planning computed tomography, a 6.8-cm heterogeneous mass was noted in the surgical bed. Given the tumor's aggressive nature and positive surgical margins, there was real concern for recurrent disease. Further evaluation with magnetic resonance imaging elucidated that the mass consisted of simple fluid and fat, without contrast enhancement, suggesting a postoperative fluid collection. He was able to continue with adjuvant treatment as planned. This case example illustrates that even large postoperative heterogeneous masses may still be related to postoperative fluid collection in patients with aggressive tumor. However, it is important to rule out recurrent disease before starting adjuvant therapy given improved outcomes with gross total resection in desmoplastic small round cell tumor.

Prospective Evaluation of Ultrasound Accuracy in the Detection of Pelvic Carcinomatosis in Patients with Ovarian Cancer

We analyzed the accuracy of transvaginal sonography in detection of pelvic carcinomatosis in ovarian cancer patients and factors (age, body mass index, performance status, ascites, stage, histotype, tumor grade) influencing the performance of ultrasound. In this prospective study, all 191 consecutively included patients underwent a pre-operative ultrasound staging examination according to institutional protocol. Peritoneal spread was assessed on the basis of peri-operative findings or histology. The area under the receiver operating characteristic curve for the detection of carcinomatosis was 0.90 (0.84-0.93); the sensitivity was 84% (95% confidence interval [CI]: 75%-%90), specificity 96% (95% CI: 89%-99%), positive predictive value 96% (95% CI: 89%-99%), negative predictive value 83% (95% CI: 74%-90%) and overall accuracy 89% (95% CI: 84%-93%). We report that transvaginal sonography is clinically useful in the detection of pelvic carcinomatosis.

Peritoneal lymphomatosis confused with peritoneal carcinomatosis due to the previous history of gastric cancer: a case report

Peritoneal lymphomatosis is a very rare disease of extranodal involvement of malignant lymphoma that is occasionally confounded with other peritoneal diseases. Herein, we reported the case of a 59-year-old woman who presented with massive ascites with prior history of stomach perforation during endoscopic procedure to treat early gastric cancer. Imaging studies showed massive ascites and tumor infiltration in the omentum and peritoneal wall. Initially, relapsed gastric cancer with peritoneal seeding was suspected based on the patient's history and imaging findings. However, final diagnosis was confirmed by ascites cytology as peritoneal lymphomatosis of diffuse large B-cell lymphoma unlike prior clinical information.