Retroperitoneal Tumors and Sarcomas

These flashcards cover important concepts and details related to retroperitoneal tumors and sarcomas, aiding in exam preparation.

What is the retroperitoneum bounded by anteriorly?

The peritoneum, ipsilateral colon and mesocolon, pancreas, liver, or stomach.

What muscle groups form the posterior margin of the retroperitoneum?

The psoas, quadratus lumborum, transverse abdominal, and iliacus muscles.

What is the incidence of malignant tumors compared to benign tumors in the retroperitoneum?

Malignant tumors occur four times more frequently than benign lesions.

What type of tumors comprise a third of retroperitoneal tumors?

Sarcomas.

What are the two broad categories of sarcomas?

Soft tissue sarcomas and bone sarcomas.

What percentage of all adult malignancies do sarcomas account for?

Approximately 1%.

What are the most common subtypes of soft tissue sarcomas (STS)?

Undifferentiated pleomorphic sarcoma, GISTs, liposarcoma, leiomyosarcoma, synovial sarcoma, and malignant peripheral nerve sheath tumors.

What percentage of neoplasms arising in the retroperitoneum are malignant?

Approximately 80 percent.

What is the most common histologic type of retroperitoneal sarcoma in adults?

Liposarcoma (70%).

How many subtypes of liposarcoma are there?

Three: well-differentiated, dedifferentiated, and pleomorphic.

What does leiomyosarcoma show differentiation in?

Smooth muscle.

Which imaging technique is preferred for pre-resection biopsy?

Image-guided core needle biopsy.

What syndrome is associated with a TP53 germline mutation?

Li-Fraumeni syndrome.

What indicates unresectability in retroperitoneal sarcoma?

Extensive vascular involvement, peritoneal implants, distant metastases, and involvement of mesenteric vessels.

What is the primary oncologic goal for surgical resection of retroperitoneal STS?

Complete resection with microscopically negative margins (R0 resection).

What is a common post-surgical complication with retroperitoneal sarcomas?

Local recurrence.

Which type of radiotherapy is used more frequently for high-grade retroperitoneal STS?

Preoperative radiation therapy (RT).

What type of tumors arise more commonly in the abdominal cavity compared to STS?

Tumors that metastasize to the liver and peritoneum.

Regarding staging, what does the term TX indicate?

Primary tumor cannot be assessed.

What does T1 represent in tumor staging?

Tumor ≤ 5 cm in greatest dimension.

What type of resection may be required to achieve complete resection of retroperitoneal tumors?

Resection of adjacent organs such as the small bowel, colon, or kidney.

What does R1 resection indicate?

Grossly complete resection with microscopically positive margins.

Why is preoperative RT often preferred over postoperative RT?

It allows the delivery of higher doses safely, avoiding risks to surrounding organs.

What is a significant complication associated with postoperative RT for retroperitoneal sarcomas?

Narrow therapeutic ratio due to radiosensitive normal structures nearby.

In what condition should patients consider further genetic assessment?

Families with a history suggestive of Li-Fraumeni syndrome.

What are the key factors influencing the prognosis of retroperitoneal STS?

Histologic grade and resection margins.

What is the common site of distant metastases for retroperitoneal sarcomas?

Liver and lungs.

What percentage of retroperitoneal sarcomas are high-grade tumors?

Approximately one-half.

What type of tumors does Gardner syndrome predispose individuals to?

Desmoid tumors.

What is the typical treatment approach for localized retroperitoneal STS?

Surgical resection.

What tumor size is classified as T2?

Tumor > 5 cm to ≤ 10 cm in greatest dimension.

What does M0 indicate in distant metastasis staging?

No distant metastasis.

What are common primary sites for soft tissue sarcoma?

Extremities, trunk, visceral, retroperitoneal, and head and neck.

What is the treatment for unresectable retroperitoneal STS?

No survival benefit for incomplete resection (debunking).

What is the main characteristic of malignant peripheral nerve sheath tumors?

They arise from peripheral nerves and have variable histology.

In what patient population are extraskeletal Ewing sarcoma and PNET most common?

Children.

What treatment modality is often used after resection of retroperitoneal STS?

Adjuvant radiation therapy.

What is the definition of G3 in histologic grading?

Grade 3, indicating poorly differentiated tumors.

What is the prognosis for retroperitoneal sarcomas compared to STS in other sites?

Less satisfactory outcomes and a higher rate of recurrence.

What is a characteristic finding of dedifferentiated liposarcoma on imaging?

A solid mass with a surrounding fat-dense well-differentiated component.

Which imaging technique is essential for workup before therapy for STS?

Chest, abdomen, and pelvis CT with contrast.

Which syndrome includes gastric stromal sarcoma and paragangliomas?

Carney-Stratakis syndrome.

What does G1 indicate in histologic grading?

Grade 1, indicating well-differentiated tumors.

What type of sarcoma is related to smooth muscle differentiation?

Leiomyosarcoma.

Which methodology can improve the delivery of radiation doses in the postoperative setting?

Intensity-modulated radiation therapy (IMRT) or proton beam irradiation.

What is the common site of first recurrence for retroperitoneal STS?

Local site, as opposed to distant sites in extremity sarcomas.

What does N1 indicate in regional lymph nodes staging?

Regional lymph node metastasis.