Review Question - QID 219538

Figure A demonstrates a microscopic evaluation of the resected tumor (hypercellular tissue, lower portion of the image) with a red dashed line through the rim of surrounding normal fat tissue. This type of resection is defined as a wide resection (Answer 4; Illustration A).

Various methods of sarcoma removal may be performed depending on the histologic diagnosis and intended treatment. In the setting of soft tissue sarcomas, wide excision of the tumor with a peripheral rim of normal tissue (i.e., wide resection; Figure A) results in lower rates of local tumor recurrence and, in many studies, improved long-term survival rates. After the soft tissue sarcoma is removed, it is sent as a large tissue block to a pathologist for examination. The pathologist will coat the block of tissue in a special ink stain and then look at various slices of the specimen under microscopic evaluation to determine if the entire tumor was removed or if there was an area of tumor potentially left behind. Dr. Enneking originally described his tumor margins classification (Illustration B), which has been widely used for decades. Contemporary classifications include the R-classification (Illustration C) and a newer R+1 classification. Positive margins may warrant adjuvant radiation (i.e., boost radiation) or even a second surgery to perform tumor bed excision.

Dr. William Enneking provided his classic proposed musculoskeletal staging system for sarcomas. This classification was based on the grade of the tumor, whether it remained intracompartmental, and if there were any distant metastases. Dr. Enneking also discussed the type of resection that should be performed, balancing the importance of local tumor control and overall limb function.

Endo and Lin comprehensively reviewed the various margin classifications for soft tissue sarcomas. They discuss the Enneking classification, R-classification (American Joint Committee on Cancer, AJCC), and R+1 classification (International Union Against Cancer, UICC). While no classification has proven superiority, they all have shown that microscopically negative margins consistently prove to have the lowest rate of local recurrence and, in many cases, improved survival rates. The authors also discuss nuances and special circumstances around margins and certain soft tissue sarcoma subtypes. They conclude that curative surgery for extremity soft tissue sarcomas should always aim for an R0 resection (i.e., microscopically negative margins).

Figure A demonstrates the microscopic examination of a resected soft tissue sarcoma. The red dashed line is denoted through the surrounding fat layer (note: the hypercellular tumor is at the lower end of the image). Illustration A shows the same image with Enneking’s marginal classification layers labeled. Illustration B shows the originally described Enneking marginal classification. Illustration C shows the AJCC’s R classification.

Incorrect Answers:
Answer 1: “Intralesional” margins are obtained when the dissection passes within the tumor, meaning the pseudocapsule was violated during surgery.
Answer 2 and 3: “Marginal” margins are obtained when the tumor is removed through the pseudocapsule. Given that microscopic tumor cells may have invaded the capsule into the surrounding reactive zone (Illustration A), some authors utilize the reactive zone as the reference point for marginal resection. In either case, these margins are sometimes intentionally left behind when removing a soft tissue sarcoma that abuts a critical neurovascular structure to retain limb function.
Answer 5: “Radical” margins are obtained by removing the tumor, pseudocapsule, reactive zone, and entire muscles or bone involved far beyond the normal plane of tissue. This would be best described as removing the entire compartment where the tumor resides or performing an amputation of the entire extremity involved.