As nature has taught us over the years, cancer can manifest in almost any region of the body. One region it does not present as frequently is the retroperitoneal (RP) space. The infrequent occurrence of this disease can make the diagnosis more challenging, particularly if a physician has not come across it previously and is not aware of the variety of symptoms that indicate an RP mass. 

The RP space is located within the abdomen and behind the peritoneum–a serous lining covering many of the abdominal organs. There are several organs contained in the RP space including the aorta, inferior vena cava (IVC), thoracic part of the esophagus, head and body of the pancreas, the kidney and ureters, adrenal glands second through fourth parts of the duodenum, ascending and descending colon, and rectum.

RP masses can be found internally (within these organs) or externally, at which point its location will directly impact how the patient clinically presents. For example, RP masses located near the kidney and ureters can cause a patient to present with decreased urinary output, flank pain, and renal failure. An RP mass near the duodenum can manifest with gastric outlet obstruction leading to nausea, vomiting, and early satiety in patients. Occasionally, patients also experience nonspecific symptoms including vague abdominal pain, weight loss, general malaise, and nausea. Therefore, a high index of suspicion is needed in order to include RP masses as a part of the differential diagnoses of common complaints such as nausea and abdominal pain.

Regardless of whether an RP mass is suspected as the primary cause of the patient’s symptoms or if it happens to be an incidental finding on imaging, CT scans or MRI are usually the radiologic tests of choice. Of the primary RP masses identified on imaging, approximately 70% to 80% are malignant and represent less than 0.5% of all malignancies found in the body1. RP masses are typically biopsied in order to identify the exact tissue and staging. Biopsies can be CT-guided and are often performed with the help of interventional radiologists.

Based on theradiologic findings and clinical presentation of RP masses, they can usually be preliminarily labeled as neoplastic or non-neoplastic. Amongst the neoplastic RP masses, they can be further subdivided into malignant versus benign. The pathology results of the biopsy will eventually help make the formal tissue diagnosis and stage. There are numerous types of malignant RP masses; however, some of the more common diagnoses include sarcomas (eg, liposarcoma, leiomyosarcoma), nerve cell derivatives (eg, schwannomas, pheochromocytomas), and germ cell tumors (eg, seminomas, malignant teratomas)2. Benign neoplasms include lipomas, fibromas, and gastrointestinal stromal tumors. The treatment regimens vary based upon the tissue diagnosis and staging, but can include surgery, radiation, and chemotherapy.

RP masses represent a somewhat uncommon yet unique subset of neoplasms; unfortunately, they can easily be forgotten when formulating a differential diagnosis for common complaints such as flank and abdominal pain. As with many deadly cancers, the malignant variety of RP masses usually present with extensive local involvement and occasional metastases. Therefore, a second thought should be given in patients presenting with non-specific symptoms, as it can be caused by a serious, underlying pathological process. 


References

1. Neville A, Herts BR. CT characteristics of primary retroperitoneal neoplasms. Crit Rev Comput Tomogr. 2004;45(4):247-70.

2. Rajiah P, Sinha R, Cuevas C, et al. Imaging of uncommon retroperitoneal masses. Radiographics. 2011 Jul-Aug;31(4):949-76. doi: 10.1148/rg.314095132.