Surgical Margins

Robert Quinn

Appropriate surgical planning for the treatment of musculoskeletal tumors requires proper histologic diagnosis and staging. The type of surgical margin most appropriate for a given tumor is, to a large extent, dictated by the appropriate stage.

Terminology

The pathologic definitions in Table 4.1-1 are essential to the understanding of surgical margins.

Surgical Margins

The surgical procedures and margins are defined in Table 4.1-2.

Surgical Procedures

Principles of Selecting the Appropriate Surgical Procedure

Selection of the most appropriate surgical margin is dependent upon the overall treatment goals of the patient.
Table 4.1-3 shows some example tumor types according to surgical stage for each type of surgical procedure.
If the goal of treatment is to establish the best chance of cure, then the most appropriate margin is that which will provide the lowest risk of local recurrence.
- Life-threatening malignancy: successful limb salvage is a secondary goal, and margins should not be
  compromised in an effort to save a limb or improve its function.
- Most aggressive benign tumors: rarely life- or limb-threatening, and these are often best treated with a less aggressive procedure, accepting a low rate of local recurrence in exchange for improved functional outcome

Table 4.1-1 Terms Pertaining to Surgical Margins

Term	Definition
Reactive zone	Area, or potential area, between the tumor and normal tissue; it may be composed of variable amounts of pseudocapsule, satellite tumor lesions, and reactive tissue, including edema
Satellite lesion	Nodules of isolated tumor within the reactive zone
Skip lesion	Nodule of isolated tumor within the same compartment as the primary tumor but separated by an interval of normal tissue beyond the reactive zone

Table 4.1-2 Definitions of Surgical Procedures Related to Margins

Procedure	Definition
Intralesional	Procedure performed within the capsule or pseudocapsule of the tumor. This is generally a curettage type of procedure for bone tumors and piecemeal excision for soft tissue tumors. By definition, macroscopic disease is left behind. An intralesional margin is obtained when the plane of dissection passes within the lesion.
Extended intralesional	Procedure performed intralesionally but extended beyond the confines of the tumor reactive zone into normal tissue by use of mechanical or other adjunctive means. This usually applies to low-grade aggressive bone lesions, where the outer border of a standard curettage is extended mechanically with aggressive use of curettes, a high-speed bur, or both, into normal surrounding bone. The bone margin may also be extended by the use of chemical (phenol), electrical, or laser cauterization, thermal effect of curing bone cement, and freezing effect of liquid nitrogen.
Marginal	Procedure performed within the reactive zone of the lesion. This is typically an en bloc type of resection for soft tissue tumors such as excision of a lipoma. For intraosseous bone tumors, a marginal excision would be an “extended curettage.” For surface bone tumors, a marginal excision would be accomplished by simple excision of the lesion without any surrounding tissue. A marginal margin is obtained when the plane of dissection passes through the reactive zone. Microscopic disease may be left behind where portions of the tumor itself extend into the reactive zone or where satellite lesions are present. A marginal resection or amputation risks leaving satellite lesions behind.
Wide	Procedure performed entirely through normal tissue beyond the reactive zone. It reflects not the amount of normal tissue that makes up the margin but simply the presence of some amount of normal tissue between the reactive zone and the plane of dissection. A wide procedure only risks leaving skip lesions behind.
Radical	Procedure in which the entire compartment of origin is removed
Contaminated margin	If, during the process of performing a wide or radical resection, the tumor is inadvertently entered and local normal tissue exposed, the area is at increased risk for local recurrence of the tumor. If the at-risk tissues are then removed with a wide margin, the ultimate margin is said to be a contaminated wide margin. If the at-risk tissues are not removed, the ultimate margin is intracapsular.