59

Retroperitoneal Tumors

Louis L. Pisters; Philippe E. Spiess; Dan Leibovici

Questions

1.Which of the following is NOT considered an etiologic factor for soft tissue sarcoma?

a.Viral infection

b.Previous radiation exposure

c.Scar tissue from previous injury

d.Retroperitoneal fibrosis

e.Gardner syndrome

2.Which of the following considerations does NOT support the dormant embryonal stem-cell origin theory of sarcoma pathogenesis?

a.Occasional malignant transformation of hemangiopericytoma into hemangiosarcoma

b.The occasional occurrence of heterotopic tissue in a retroperitoneal sarcoma

c.The occurrence of dedifferentiated liposarcoma

d.The fact that mesenchymal tissue turnover is much slower than that of mucosal linings

e.The possible occurrence of sarcoma in very young children

3.Genetic aberrations associated with soft tissue sarcomas include which of the following?

a.Ring chromosome 12 is commonly found in malignant fibrous histiocytoma

b.Deletions of suppressor gene pRb are detected in pleomorphic liposarcoma

c.Translocation between chromosomes 12 and 16 is observed in myxoid liposarcoma

d.Translocation of chromosome 7p to 12q is observed in leiomyosarcoma

e.Aneuploidy is a normal finding in schwannomas

4.A patient undergoes surgical resection of a poorly differentiated retroperitoneal liposarcoma. There was macroscopic residual tumor. In terms of surgical staging, the patient would be considered:

a.Rx.

b.R0.

c.R1.

d.R2.

e.R3.

5.Which of the following may represent a malignant lesion if greater than 6 cm?

a.Rhabdomyoma

b.Aggressive fibromatosis

c.Pelvic lipomatosis

d.Lipoblastoma

e.Leiomyoma

6.Any fat-containing retroperitoneal mass, until proven otherwise, should be considered:

a.a renal angiomyolipoma.

b.an adrenal myelolipoma.

c.a well-differentiated liposarcoma.

d.an adrenal pheochromocytoma.

e.an osteosarcoma.

7.A pretreatment retroperitoneal mass biopsy should be obtained using:

a.an image-guided biopsy, preferably using a retroperitoneal approach.

b.an open or laparoscopic guided biopsy if possible.

c.a fine-needle aspiration technique as more diagnostic.

d.any technique necessary as required to diagnose a retroperitoneal sarcoma in all cases.

e.an endoscopic technique in all cases because it avoids potential seeding of the peritoneum.

8.Postoperative radiotherapy should be considered:

a.if it can compensate for an incomplete resection or positive surgical margins.

b.based on careful review of an individual case and not solely on the margin status at the time of the initial or re-resection.

c.if negative margins have been obtained at the time of the original resection.

d.if positive microscopic surgical margins have been obtained but the surgeon feels that all gross disease has been resected.

e.if a radiation oncologist deems it to beneficial.

9.The adjuvant systemic regimen best studied in the management of retroperitoneal soft tissue sarcoma following surgical resection is:

a.single-agent gemcitabine.

b.targeted therapy using pazopanib.

c.single-agent doxorubicin.

d.combination therapy using epirubicin and ifosfamide.

e.single-agent trabectedin.

.The most important determinant of the likelihood of sarcoma recurrence following surgical status is:

a.sarcoma histologic subtype.

b.tumor grade.

c.tumor ploidy.

d.presence of lymphovascular invasion.

e.final surgical margin status.

Answers

1.d. Retroperitoneal fibrosis. Of the clinical parameters listed, only retroperitoneal fibrosis is not an etiologic factor associated with development of a soft-tissue sarcoma. When a patient presents with retroperitoneal fibrosis, a malignancy such as a soft-tissue sarcoma is in the differential diagnosis, but that does not mean it constitutes an etiologic factor. The remaining choices— viral infection, previous radiation exposure, scar tissue from a previous injury, and Gardner syndrome—are all etiologic factors with soft-tissue sarcomas.

2.a. Occasional malignant transformation of hemangiopericytoma into hemangiosarcoma. It is rare for a benign entity such as a hemangioma or hemangiopericytoma to differentiate into a malignant hemangiosarcoma; therefore this does not support the dormant embryonal stem-cell origin theory. The remaining choices are all correct and support this theory.

3.c. Translocation between chromosomes 12 and 16 is observed in myxoid liposarcoma. Genetic aberrations including a balanced translocation of

chromosomes 12 and 16 t(12:16) (q13:p11) appear in 90% of myxoid liposarcoma cases and are pathognomonic of this sarcoma (Eneroth et al, 1990).* The remaining choices are all incorrect.

4.d. R2. The presence of macroscopic residual tumor following surgical resection renders the patient R2. R0 represents tumor that was entirely resected with no residual tumor and negative surgical margins; R1 represents microscopic residual tumor (i.e., a positive surgical margin); R2 represents macroscopic residual tumor; and R3 represents tumor spillage and dissemination at the time of resection.

5.e. Leiomyoma. Distinguishing a leiomyoma from a leiomyosarcoma can be difficult under rigorous microscopic pathology review, but parameters suggestive of malignancy include tumor size, pleomorphism, cellularity, necrosis, atypia, and mitosis. Hence, of the choices given, leiomyoma is the correct answer.

6.c. A well-differentiated liposarcoma. Retroperitoneal liposarcomas are the most common type of retroperitoneal soft tissue sarcomas. Based in large part on this important fact, any fat-containing retroperitoneal mass should be considered a well-differentiated liposarcoma until proven otherwise. All other choices are incorrect.

7.a. An image-guided biopsy, preferably using a retroperitoneal approach.

Many experts feel that a pretreatment biopsy should be obtained (whenever feasible) using an image-guided and, if possible, a retroperitoneal approach to minimize the risk of cancer spillage/dissemination. The other choices are incorrect because they are not the preferred diagnostic approach to obtaining a pretreatment biopsy, although they are occasionally obtained when an image-guided biopsy is not technically feasible.

8.b. Based on careful review of an individual case and not solely on the margin status at the time of the initial or re-resection. Postoperative radiotherapy should be offered to patients based not solely on their margin status at the time of surgical resection (either primary or redo) but rather on the individual characteristics of the case. All other choices are incorrect.

9.d. Combination therapy using epirubicin and ifosfamide. The combination of the systemic agents epirubicin and ifosfamide are the best studied in the management of retroperitoneal soft-tissue sarcomas (and overall soft-tissue sarcomas for that matter). This systemic chemotherapy combination has been used in pivotal trials of perioperative systemic therapy. Other systemic agents such as single-agent gemcitabine, doxorubicin, and trabectedin as well as

targeted agents (e.g., pazopanib) have not been as well studied in the management of retroperitoneal sarcomas and hence are incorrect choices to this question.

.e. Final surgical margin status. The final surgical margin status is the most important prognostic factor of the likelihood of recurrence. Although other options listed, such as tumor grade and ploidy, have prognostic importance for retroperitoneal sarcomas, they are of lesser importance in predicting the likelihood of recurrence following surgical resection; hence the remaining choices are incorrect.

Chapter review

1.Retroperitoneal sarcomas have a propensity for hematogenous spread— usually to the lung and liver.

2.Pelvic lipomatosis is a hyperplastic rather than a neoplastic process.

3.Myelolipoma usually occurs in the adrenal gland but may be found in the retroperitoneum.

4.Sarcomas have a tendency to recur, in part owing to pseudoencapsulation and the false gross appearance of complete surgical resection. Surgical margin status is the most important prognostic indicator for local recurrence and survival.

5.Rhabdomyosarcomas are classified as embryonal, alveolar, and undifferentiated.

6.Sarcomas arise de novo and not from malignant transformation of a benign tumor.

7.Liposarcoma, leiomyosarcoma and malignant fibrous histiocytoma make up 80% of retroperitoneal sarcomas. Liposarcoma is the most common type of retroperitoneal soft tissue sarcoma.

8.Radiation therapy has been shown to be beneficial in selected circumstances and may be given preoperatively, intraoperatively, or postoperatively.

9.Tumor involvement of neural foramina suggests unresectability.

10.Staging of retroperitoneal sarcomas: R0 represents tumor that was entirely resected with no residual tumor and negative surgical margins; R1 represents microscopic residual tumor (i.e., a positive surgical margin); R2 represents macroscopic residual tumor; and R3 represents tumor spillage and dissemination at the time of resection.

11.Surgical margin status is the most important prognostic factor of the

likelihood of recurrence. Tumor grade and ploidy also have prognostic importance, but to a lesser degree.

* Sources referenced can be found in Campbell-Walsh Urology, 11th Edition, on the Expert Consult website.