The retroperitoneum can be habitat to a wide range of diseases, including rare benign tumors and diseases that might be primary or metastatic. The incidence of malignant tumors of the retroperitoneum is four times higher than that of benign lesions. A third of retroperitoneal tumors are sarcomas. Soft tissue sarcomas are uncommon tumors, with retroperitoneal sarcomas accounting for about 17% of the 2,000 cases of soft tissue sarcomas estimated each year in England and Wales. Each year, between 255 and 300 new cases of retroperitoneal sarcoma (RPS) are diagnosed in the United Kingdom. After the lower extremities, the retroperitoneum is the second most frequent site of development of malignant mesenchymal tumors. Because of their late-onset and anatomical location, retroperitoneal tumors present a number of therapeutic difficulties.
Because of their rarity, difficulty in identification, high recurrence rate following surgical removal, and unpredictable response to adjuvant treatment, retroperitoneal tumors in the pelvis are a challenging surgical pathology entity. Retroperitoneal tumors are frequently diagnosed late, in the advanced stages of local or systemic metastasis, due to their inaccessible anatomical location and late clinical presentation. As a result, many of these patients do not benefit from total surgical excision, leaving gynecologists with a significant diagnostic and therapeutic dilemma.
The retroperitoneum is a complex potential area that is bounded anteriorly by the peritoneum, posteriorly by the posterior abdominal wall, superiorly by the 12th rib and vertebra, inferiorly by the base of the sacrum and iliac crest, and laterally by the quadratus lumborum muscle boundaries. The connective tissue, kidneys, ureters, adrenal glands, aorta and its branches, inferior vena cava and its tributaries, and lymph nodes are all contained inside this space.
Retroperitoneal sarcomas are extremely rare tumors, accounting for just 1%–2% of all solid tumors. The majority of sarcomas originate outside of the retroperitoneum. Retroperitoneal sarcomas account for only 11–21% of all sarcomas, with an overall incidence of 0.4–0.5% per 100,000 people. The incidence is highest in the fifth decade of life, but it can happen at any age. From study to study, the most common kinds of retroperitoneal soft tissue tumors in adults differ. Liposarcomas, leiomyosarcomas, and malignant fibrous histiocytomas are the most commonly observed cell types in most investigations. The common diagnosis of malignant fibrous histiocytomas in the retroperitoneum has lately been questioned. Many of these fibrous tumors have recently been demonstrated to represent other sarcoma forms, such as leiomyosarcomas or undifferentiated liposarcomas, using immunohistochemistry. As a result, it is expected that the number of these malignancies classified as malignant fibrous histiocytomas in the future will be significantly reduced.
Retroperitoneal Tumor Types
Knowing the differential diagnoses for a retroperitoneal tumor will enable the gynecologist to be aware of the essential preoperative diagnostics and referrals in order to maximize the patient's care.
Retroperitoneal tumors are uncommon tumors that arise from the retroperitoneal spaces rather than from the main retroperitoneal organs. Retroperitoneal tumors can be classified according to their tissue of origin. Retroperitoneal tumors have been classified as solid or cystic tumors. Because gynecologists typically rely on imaging to diagnose retroperitoneal tumors, one of the most important radiological characteristics is whether the tumor is solid or cystic. The majority of retroperitoneal tumors are mesodermal in nature and can emerge from any type of retroperitoneal tissue. They can be either benign or malignant.
Benign tumors are frequently discovered as a result of examinations into unrelated symptoms. Schwannomas, neurofibromas, ganglioneuromas, paragangliomas, fibromatosis, and lipomas are the most frequent benign retroperitoneal tumors.
Sarcomas account for a third of all retroperitoneal tumors, with liposarcomas and leiomyosarcoma being the most common. Lymphomas, malignant fibrous histiocytomas, desmoid tumors, extragonadal germ cell tumors, and metastatic retroperitoneal lymphadenopathy are among the other malignant retroperitoneal tumors.
Retroperitoneal Tumor Symptoms
Ovarian cancers are frequently misinterpreted as retroperitoneal tumors. Because the ultrasound findings and clinical symptoms of a retroperitoneal cyst and an ovarian cyst are so identical, it's incredibly harder to say the two apart.
Retroperitoneal tumors create compression of the structures in the retroperitoneum, which can cause obstruction. Symptoms are vague and arise late in the course of the disease. On clinical evaluation, most patients will have abdominal pain and distension, as well as a palpable lump. A large number of benign retroperitoneal tumors are discovered by chance during imaging for unrelated symptoms. Patients may also experience urinary or gastrointestinal problems as a result of the huge tumors' pressure on these organs.
Between 1999 and 2009, Gatita and colleagues conducted a retrospective examination of all patients treated for primitive retroperitoneal tumors. It's important to note that all of the retroperitoneal tumors found in their investigation were in the symptomatic stage. 84 percent of the 57 patients in this study reported abdominal discomfort, 71.5 percent reported a palpable tumor, 51.8 percent reported urine symptoms, 43 percent reported gastrointestinal symptoms, and 5.5 percent reported abdominal distension.
Retroperitoneal Tumor Diagnosis
Radiological approaches are used to identify retroperitoneal tumors, and histology is used to confirm the diagnosis. When a patient goes to the consultation clinic with abdominal pain or distension, ultrasonography (US) is frequently the initial line of examination in gynecology. The use of ultrasound to detect cystic lesions is effective and affordable, with no radiation exposure.
Computed Tomography (CT)
Contrast-enhanced computed tomography (CT) is the imaging of choice for identifying retroperitoneal malignancies. CT is crucial in the diagnosis, characterization, and assessment of the extent of local invasion, as well as the assessment of metastases and treatment response of malignant tumors. Although most retroperitoneal tumors have non-specific CT imaging findings, an imaging study of the tumor components, growth pattern, vascularity, and tumor demography can help to narrow down the differential diagnosis. Every cystic retroperitoneal pelvic tumor suspected on initial imaging should get a CT myelography to rule out Tarlov cyst (perineurial cyst), as this would change the therapy. Asymptomatic Tarlov cysts are normally left alone; however, symptomatic Tarlov cysts should be referred to neurosurgeons for further therapy.
Magnetic Resonance Imaging (MRI)
Magnetic resonance imaging (MRI), while more expensive than CT, is becoming more common in the assessment of retroperitoneal soft-tissue tumors due to its superior tissue characterization and spatial resolution. However, unlike CT, the MRI characteristics of most retroperitoneal tumors are non-specific, making it difficult for radiologists to anticipate an accurate histological diagnosis. The vascularity of masses is reflected in the dynamic enhancing patterns in MRI, which helps to distinguish benign from malignant retroperitoneal tumors. High-resolution MRI's tissue-specific multiplanar capability enables improved tumor localization and internal characterization and hence serves as a road map for surgical planning.
Retroperitoneal Tumor Surgical Treatment
Although complete surgical removal is the only potentially curative treatment option for RPS, local recurrence affects a substantial percentage of patients and accounts for up to 74% of sarcoma-related fatalities. Complete macroscopic excision, tumor grade, multifocality, and histological subtype are known prognostic markers for local recurrence and overall survival in RPS. RPS has a substantially worse prognosis than extremities sarcomas, with a five-year local recurrence-free survival rate of 54 to 79 percent following full resection and a five-year overall survival rate of 40 to 69 percent. This is due to the fact that they are typically larger and develop in an anatomically difficult and surgically inaccessible location with important structures surrounding them limiting wide margins. They are frequently unresponsive to traditional radical radiation. The chance of a complete margin-negative surgical removal is impacted by tumor biology, as well as invasion of surrounding visceral organs and vascular structures. Surgical skills and management in high-volume centers may also play a role.
Resection of neighboring affected organs is frequently required, with rates of adjacent viscera resection ranging from 35-94% in large series, although macroscopic clearing was achieved in 60-93%. The surgical technique comprises a low threshold for organ resection in order to clear all macroscopic diseases. To achieve total macroscopic clearance, an en bloc resection of the sarcoma and neighboring organs that are macroscopically affected by the tumor or encompassed by the tumor is undertaken. Organs that are only adjacent to the tumor and are not involved are not attempted to be resected. We reported a 64 percent resection of surrounding organs, with 84 percent of patients achieving macroscopic clearance. The colon, kidney, pancreas, and spleen are the most often resected organs.
Two retrospective European studies looked at the role of liberal visceral en bloc resection in attempting to incorporate an envelope of normal tissue around the tumor to reduce resection marginality and improve outcome. It's also unclear whether selective removal of some disposable organs (colon, kidney) adjacent to the tumor while retaining other important structures (inferior vena cava, aorta, superior mesenteric artery, liver) that are also in proximity with the tumor will improve overall survival. There's no reason to believe that one of the organs forming the retroperitoneums' boundaries is more important than the others in determining local failure.
Recurrent Retroperitoneal Tumor
RPS is prone to local recurrence, which is still the leading cause of death. Tumor biology is a significant predictive factor for patients with recurrent RPS; local recurrence rates are higher and occur at a shorter interval in patients with high-grade tumors than in patients with low-grade tumors. The majority of reports on this subject are retrospective, with varying management strategies and outcomes. When patients develop new symptoms or a mass is apparent on clinical examination, a CT scan is recommended. If the patient develops serious symptoms or if further delay makes ultimate operation more difficult, additional surgery is recommended.
At the time of local recurrence, the chances of obtaining negative margins are much reduced, and each subsequent surgery is more challenging than the last. However, in symptomatic patients with first and repeated local recurrence, resection should be explored since it provides effective palliation and may increase survival in certain people. For recurrent sarcomas of low or intermediate grade, palliative surgery can be used to reduce symptoms and enhance the quality of life.
Retroperitoneal Tumor Chemotherapy
Because of the high rate of local failure, researchers are looking at using a combined modality treatment (surgery and radiotherapy) to reduce the rate of local recurrence. Radiotherapy has become standard practice in the treatment of extremities sarcomas because it improves local control. RPS, on the other hand, has a number of radiotherapeutic challenges. These tumors are frequently seen in close proximity to radiosensitive structures that have a low radiation tolerance. Retroperitoneal sarcomas are a diverse category of tumors with varying levels of radiosensitivity.
A number of retrospective and observational studies have been conducted to assess the feasibility and outcomes of preoperative, intraoperative, and postoperative radiation in the treatment of RPS. Preoperative radiotherapy has the following advantages: the tumor is clearly delineated for radiotherapy planning, the tumor is pushing some of the radiosensitive surrounding organs, and an equivalent therapeutic dosage of radiotherapy may be reduced. Based on the grade and margin status, postoperative radiation allows for the identification of individuals who are at risk for recurrence. In the postoperative situation, however, the surrounding organs will shift into the tumor bed and become adherent to it, increasing the risk of radiation-related toxicities. Studies have assessed plan of care with conformal treatments such as intensity-modulated radiotherapy or the use of intraoperative radiotherapy in an effort to minimize radiation toxicities.
Retroperitoneal Tumor Radiotherapy
Although there may be some cases when neoadjuvant/adjuvant treatment is beneficial, there is no convincing evidence of a disease-free survival advantage for the majority of histological subtypes. Chemotherapy has significantly increased survival in subtypes such as the Ewing family of tumors, for which it is an important component of primary management. Agents like doxorubicin and ifosfamide have a role to play in the treatment of symptomatic advanced sarcoma. Chemotherapy is becoming more specialized based on histological subtype, with taxanes being used for angiosarcoma, gemcitabine and docetaxel for leiomyosarcoma, and trabectedin for leiomyosarcoma and myxoid/round cell liposarcoma, for example.
Postoperative Imaging Follow-up
Despite complete resections, 5- and 10-year survival rates are low, at 50% and 37%, respectively. Local recurrences in the surgical bed are the most common cause of this. The majority of tumor recurrences happen within two years of the first surgical excision. Because the ability to completely resect local recurrences affects subsequent prognosis in these cases, early diagnosis of tumor recurrence is essential. Re-resections are efficient in up to 92% of patients when conducted early. Sadly, many recurrences are discovered late in the course of the disease, resulting in inadequate resection and, in about half of the cases, recurrence.
Because most recurrences are localized, follow-up imaging should be evaluated for minor changes in the surgical bed. Clinical follow-up is frequently ineffective because up to half of the patients are asymptomatic, and if symptoms do exist, they are often nonspecific.
Early local recurrences can be hard to detect. Recurrences of soft-tissue attenuation may be difficult to distinguish from post-operative scarring in the surgical bed. Local recurrence identification in liposarcomas is particularly problematic because recurrent liposarcomas can be difficult to differentiate from normal retroperitoneal fat on imaging when they are tiny. Closer examination often reveals that the fat in a recurrent liposarcoma has a somewhat higher CT attenuation than normal retroperitoneal fat. Recurrent liposarcomas can also have imaging properties that differ from those of the main tumor. Four of the eight recurring liposarcomas in a CT investigation of fat-containing liposarcomas had no apparent fat. Because recurrent tumors respond well to surgical removal, all tumor-bearing locations should be recognized to allow for optimal and full resection. Regional metastases are also common, so before evaluating for distant metastases, a comprehensive investigation of the draining nodes, peritoneal surfaces, and liver should be performed.
Follow-up imaging is typically done with CT or MRI, and the frequency of follow-up is often determined by the extent of tumor resection, tumor type, and grade. Obtaining imaging at regular intervals (e.g., CT or MRI every 3-4 months for two years, then every 4-6 months for five years, and every one year thereafter) is recommended follow-up program. Although most sarcomas (high-grade or low-grade) recur within three years, a significant delay in the manifestation of recurrent disease is not uncommon.
The concept of concentrating rare surgical disorders and complex surgeries in high-volume specialized centers has been a significant development in surgery over the previous decade. In major oncologic surgeries, such as hepatobiliary surgical procedures, esophagogastric surgical interventions, and surgical oncology, significant surgeon volume and specialized centers are linked to better patient outcomes. Patients with large, high-grade, and particularly retroperitoneal tumors should be addressed exclusively in high-volume centers, according to a study comparing the results between low- and high-volume centers, to make sure both enhanced short-term surgical outcomes and superior long-term local recurrence and overall survival rates. As a result, RPS management should be confined to a few highly skilled interdisciplinary centers. This will also benefit training and education.
Tumor biology research focuses on the molecular and genetic diversity of sarcomas, with the intention of developing novel biological therapeutics to target the various molecular mechanisms, comparable to the success seen with a tyrosine-kinase inhibitor in managing gastrointestinal stromal tumors. Randomized control trials are needed to determine the significance, dose, and timing of radiation in enhancing local management.
A wide range of unusual diseases, including benign and malignant tumors, can be found in the retroperitoneum. Tumors typically present late, causing symptoms or becoming palpable once they have grown large enough. Retroperitoneal tumors are best assessed with high-resolution cross-sectional imaging, and when imaging is non-diagnostic, preoperative histopathology by core needle biopsy is essential. Complete surgical excision is the only potentially curative treatment option for retroperitoneal sarcomas, and it's best done by a multidisciplinary sarcoma team in high-volume centers. A substantial percentage of patients experience local recurrence. The capacity to totally resect a retroperitoneal sarcoma, as well as the tumor grade, are still the most important indicators of local recurrence and disease-specific survival. To identify the role of radiation therapy and establish novel biological therapies to target the various molecular mechanisms, more study is needed.