Primary and secondary tumors of the peritoneum: key imaging features and differential diagnosis with surgical and pathological correlation.

Peritoneal malignancies represent a diagnostic challenge for abdominal radiologists, oncologists, surgeons and pathologists in multidisciplinary teams, who must address their differential diagnosis, staging and treatment. In this article, we explain the pathophysiology of these processes and lay out the role of different imaging techniques in their evaluation. Then, we review the clinical and epidemiological aspects, the main radiological features and the therapeutic approaches for each primary and secondary peritoneal neoplasm, with surgical and pathological correlation. We further describe other rare peritoneal tumors of uncertain origin and a variety of entities that may mimic peritoneal malignancy. Finally, we summarize the key imaging findings of each peritoneal neoplasm to facilitate an accurate differential diagnosis that may impact patient management.Clinical relevance statementImaging plays an essential role in the evaluation of peritoneal malignancies, assessing their extension, detecting unfavorable sites of involvement and facilitating an accurate differential diagnosis, helping to choose the best therapeutic approach.

Adjuvant therapy sparing in rectal cancer achieving complete response after chemoradiation.

AIM: To evaluate the long-term results of conventional chemoradiotherapy and laparoscopic mesorectal excision in rectal adenocarcinoma patients without adjuvant therapy. METHODS: Patients with biopsy-proven adenocarcinoma of the rectum staged cT3-T4 by endoscopic ultrasound or magnetic resonance imaging received neoadjuvant continuous infusion of 5-fluorouracil for five weeks and concomitant radiotherapy. Laparoscopic surgery was planned after 5-8 wk. Patients diagnosed with ypT0N0 stage cancer were not treated with adjuvant therapy according to the protocol. Patients with ypT1-2N0 or ypT3-4 or N+ were offered 5-fluorouracil-based adjuvant treatment on an individual basis. An external cohort was used as a reference for the findings. RESULTS: One hundred and seventy six patients were treated with induction chemoradiotherapy and 170 underwent total mesorectal excision. Cancer staging of ypT0N0 was achieved in 26/170 (15.3%) patients. After a median follow-up of 58.3 mo, patients with ypT0N0 had five-year disease-free and overall survival rates of 96% (95%CI: 77-99) and 100%, respectively. We provide evidence about the natural history of patients with localized rectal cancer achieving a complete response after preoperative chemoradiation. The inherent good prognosis of these patients will have implications for clinical trial design and care of patients. CONCLUSION: Withholding adjuvant chemotherapy after complete response following standard neoadjuvant chemoradiotherapy and laparoscopic mesorectal excision might be safe within an experienced multidisciplinary team.

Retroperitoneal fibrosis: role of imaging in diagnosis and follow-up.

Retroperitoneal fibrosis (RPF) encompasses a range of diseases characterized by proliferation of aberrant fibroinflammatory tissue, which usually surrounds the infrarenal portion of the abdominal aorta, inferior vena cava, and iliac vessels. This process may extend to neighboring structures, frequently entrapping and obstructing the ureters and eventually leading to renal failure. The idiopathic form of RPF accounts for more than two-thirds of cases; the rest are secondary to factors such as drug use, malignancies, or infections. If promptly diagnosed and treated, idiopathic and most other benign forms of RPF have a good prognosis. In contrast, malignant RPF, which accounts for up to 10% of cases, has a poor prognosis. Therefore, the most important diagnostic challenge is differentiation of benign from malignant RPF. Imaging plays a key role in diagnosis of RPF. Cross-sectional imaging studies, particularly multidetector computed tomography (CT) and magnetic resonance (MR) imaging, are considered the imaging modalities of choice. Imaging features may help distinguish between benign and malignant RPF, but in some cases histopathologic examination of the retroperitoneal tissue is needed for definitive diagnosis. CT and MR imaging, along with positron emission tomography with fluorine 18 fluorodeoxyglucose, also play an important role in management and follow-up of idiopathic RPF.