Tumor Biology

Primary malignant tumors have the capacity to metastasize to distant sites. They also are locally aggressive, destroy bone, and involve adjacent soft tissue structures. Malignant tumors are typically subclassified as low, intermediate, or high grade based on the histologic grade. Grade is a feature of the amount of cellular activity, cellular pleomorphism, mitotic activity, and tumor necrosis. It is reflective of the tumor’s aggressiveness.

Malignant bone tumors spread locally by centrifugal tumor expansion. As the tumor cells divide and the mass grows, normal tissue is compressed. Microscopic pseudopods of tumor invade normal surrounding tissue. In an effort to control the tumor, an inflammatory response is established adjacent to the tumor. This reactive zone consists of inflammatory cells, edematous tissue, and neovascularity feeding the advancing tumor. The compressed normal tissue produces a pseudocapsule about the mass. Thus, the surrounding soft tissue around the malignant tumor is slowly invaded by satellites of advancing tumor. To remove the tumor completely, the resection must be well beyond the reactive zone and into normal adjacent soft tissue of bone, thus avoiding leaving satellites behind.¹² Unfortunately, current imaging modalities such as magnetic resonance imaging (MRI), positron emission tomography (PET) scan, and bone scanning cannot identify microscopic tumor extension adequately. Often, the edematous tissue can be well identified, but this really provides no clear information regarding the presence or absence of microscopic tumor satellites.

This aggressive local spread of tumor is frequently halted by anatomic barriers, such as cortical bone, periosteum, cartilage, synovium, and fascia. These barriers are relative and do not offer an absolute stopping point for tumor growth. They can be breached with tumor extension beyond their confines. However, they do serve to force tumor growth into a longitudinal pattern. Tumors can extend for great distances along bone and soft tissue planes and attain a large bulky size before being detected. Tumors that remain within the confined bone or soft tissue compartment are termed intracompartmental.² Tumors that extend out of the compartment of origin and involve adjacent structures are termed extracompartmental. As the tumor spreads, it frequently displaces rather than encases neurovascular structures. Occasionally, these structures can be circumferentially engulfed by tumor but tend to remain patent and functional unless significantly compressed by a large mass. Destruction of bone and presence of a soft tissue mass can lead to pain, the most common presenting symptom of malignant tumors of bone. The subcutaneous nature of the distal femur and proximal tibia lead to early detection of a soft tissue mass associated with a bone tumor.

Principles of Surgical Management

On completion of appropriate staging and the determination of an accurate diagnosis, attention is now turned toward treatment. Cure of malignant tumors requires local control of tumor as well as control of systemic disease. Surgical management of malignant bone tumors is often the foundation for local control. The principles of surgical management are outlined here. Adjuvant treatments for common malignant tumors are found elsewhere in this text in discussions of each of the common bone malignancies.

Surgical Margins

In collecting, analyzing, and reporting surgical data, it is imperative to use a language that is common among surgeons as to which surgical procedure has been performed. The relationship between the surgical plane of resection of the tumor and surrounding tissue is known as the surgical margin. Enneking and Shirley³ have established a nomenclature to describe oncologic surgical procedures in terms of four surgical margins. The margin can be achieved by amputation or a limb salvage procedure.

Intralesional margins are achieved if the surgical plane of dissection is through the tumor, leaving behind gross residual disease. This typically occurs when a biopsy is done but also with curettage or a debulking procedure. Tumor is obviously left behind and the procedure is not curative for malignant bone tumors. This margin is appropriate only in the palliative setting or for very low-grade lesions amenable to local control with curettage alone.

Marginal margins are achieved when the plane of dissection is the pseudocapsule itself. The main body of the tumor easily peels away from the surrounding pseudocapsule. This leads the surgeon to perform a shell-out procedure inadvertently. Failure to recognize that histologically, there is a real potential to have satellites of tumor within and beyond the pseudocapsule, which results in lack of adequate margin. Several studies have demonstrated the high rate of tumor cells in this reactive zone after a shell-out or gross total resection. Even after adjuvant therapies, local recurrence is high with a marginal margin. This is why tumor bed re-excisions are often recommended after gross total resections or shell-out procedures are performed. In tumors treated preoperatively with chemotherapy or radiation, a marginal margin can be accepted only adjacent to vital structures such as a neurovascular bundle. In this situation, the preoperative treatment would have (hopefully) sterilized any microscopic satellite lesions in these areas.

Wide margins are the most commonly achieved margins when dealing with bone malignancies. The resection plane is beyond the pseudocapsule and reactive zone. It results in a cuff of normal tissue surrounding the tumor. The specimen contains the biopsy tract (skin and underlying soft tissue), body of the tumor, pseudocapsule, reactive zone, and a cuff of normal tissue. The thickness of that cuff is subject to study and debate. It must be realized that its thickness is not as important as the concept that the cuff is wide enough to be beyond any satellite or skip lesions that may be present. A wide margin is the goal of surgical treatment in bone and soft tissue sarcomas to minimize the risk of local tumor recurrence¹² (Fig. 149-1).

Figure 149-1 Surgical specimen demonstrating wide margins following resection of distal femur. Note cuff of normal tissue surrounding the tumor and inclusion of a biopsy track.

Radical margins are achieved when the involved bone and soft tissue component are resected in their entirety. An extracompartmental resection is thus achieved. When managing tumors that are extracompartmental, the entire involved bone and involved adjacent musculature must be excised to be considered a radial resection. Radical margins are typically unnecessary for bone sarcomas.

Related posts:

Overview of Psoriatic Arthritis Anesthesia for Knee Surgery Computer-Assisted Navigation: Minimally Invasive Surgery for Total Knee Replacement Distal Realignment of the Patellofemoral Joint: Indications, Effects, Results, and Recommendations Anterior Cruciate Ligament Reconstruction With Central Quadriceps Free Tendon Graft Osteochondritis Dissecans

Stay updated, free articles. Join our Telegram channel

Join