Fig. 11.1
(a) An anteroposterior radiograph of a suspected metastatic lesion in the humeral diaphysis. (b) The solid line indicates the planed open biopsy incision, longitudinally oriented within an extensile approach, indicated by the dotted line extending proximally and distally. The dotted ellipse around the planned biopsy incision indicates an appropriate biopsy tract excision if the biopsy reveals a primary musculoskeletal malignancy
The biopsy tract should be planned to span the shortest possible distance from the skin to the lesion while being located within a single muscular compartment and away from critical neurovascular structures. In this manner, potential disease dissemination is limited to a single compartment and spares vital structures, the contamination of which compromises limb-sparing surgery. Following the procurement of a specimen, absolute hemostasis is the goal. A hematoma arising from a biopsied malignancy contains cancerous cells. An expanding hematoma may dissect through tissue planes, introducing malignant cells throughout the extremity, increasing the risk of disease dissemination and complicating limb-sparing procedures.
A bone scan may further aid in the determination of the optimal biopsy location. By identifying multifocal osseous disease, a bone scan may reveal the presence of a readily accessible osseous lesion. The histologic diagnosis of one lesion in multifocal disease is considered representative of the other lesions, assuming that they have a similar morphology [2].
When an extraosseous soft tissue mass is present, it should be biopsied preferentially in order to avoid violating cortical bone and further weakening a bone at risk of fracture. However, in the absence of tumor soft tissue extension a cortical window osteotomy may be required to access the lesion of interest. In order to minimize the structural derangement resulting from a cortical window, the osteotomy should be longitudinally oriented, be oblong in shape, and have rounded edges. The osteotomy should be narrow and enlarged longitudinally as needed. Increasing the osteotomy transversely, around the circumference of the bone, has been shown to significantly weaken a long bone, predisposing it to fracture. Cortical windowing performed in this manner is believed to preserve the structural integrity of long bones better than that of other geometries [18].
Prior to performing a biopsy, careful planning is essential. Considerations ranging from compartmental anatomy to lesion accessibility and surgical approaches for definitive management must be considered. Improperly placed biopsy tracts alter future procedures in 5 % of bone sarcomas [19]. Even when planning an intraoperative frozen section for the confirmation of metastatic disease, the initial approach should be planned with the aforementioned considerations in mind just in case the intraoperative biopsy reveals an unexpected malignant process.
Biopsy Methods
Whether an open or percutaneous biopsy is performed, appreciation for the general principles of musculoskeletal biopsies is essential. These considerations should be clearly communicated if someone other than the managing surgeon is performing the biopsy. Of equal importance is communication with the pathologist. A patient’s clinical history and diagnostic imaging provide important context, facilitating the evaluation of the histopathological specimen.
Incisional Biopsy
With diagnostic accuracy rates up to 98 %, an open incisional biopsy is considered the gold standard for obtaining a histologic diagnosis [20]. If there is a high index of suspicion for metastatic carcinoma to the bone, an incisional biopsy may be performed intraoperatively to obtain histological confirmation prior to the definitive operative procedure [21]. Alternatively, an open biopsy performed as an isolated procedure is rarely warranted as a first-line test due to increased cost, time, and risk of complications associated with the procedure compared to percutaneous options.
The principles of biopsy placement, orientation, and hemostasis are most relevant for incisional biopsies. Following open biopsies, complication rates up to 15 % have been reported in this high-risk patient population, made vulnerable by their underlying malignant pathology and their resultant therapies [19, 22, 23].
Core Needle Biopsy
Compared to open biopsies, image-guided core needle biopsies (CNB) have the advantage of being percutaneous and safe to perform [9, 24, 25]. Procedure-related sedation, recovery, cost, and complications are all lower compared to an open technique [9, 10, 25, 26]. When facilitated by image guidance, diagnostic accuracy rates for CNB have been reported between 74 and 93 % (Fig. 11.2) [9, 24–27]. These rates are predominately a reflection of the techniques’ ability to distinguish between different types of primary bone malignancies. However, for confirming the presence of metastatic carcinoma in bone, a less nuanced diagnosis, accuracy rates for CNB have been reported as high as 97 % [9, 10].
Fig. 11.2
An image-guided CNB enables tissue sampling deep structures with relatively minimal morbidity
The main advantage of a CNB over fine-needle aspiration (FNA), an alternate percutaneous modality, is its ability to retain normal tissue architecture which greatly facilitates histologic evaluation (Fig. 11.3).
Fig. 11.3
The core biopsy needle with representative specimens. Obtaining a contiguous core of tissue allows maintenance of microscopic tissue architecture to facility histologic diagnosis compared to needle aspirations
Fine-Needle Aspiration
Similar to a CNB, FNA has the advantages inherent with a percutaneous procedure. The disadvantages to FNA compared to other modalities are a relatively low rate of accuracy and the requirement of an experienced cytopathologist for specimen review. The literature reports accuracy rates between 63 and 85 % for image-guided aspirations of bone lesions [26, 28]. For each non-diagnostic sampling a repeat biopsy must be performed, causing significant increases in time, cost, and patient anxiety. Proponents of FNA report a cost saving compared to open procedures; however the additive cost of FNA and the request repeat biopsies have a greater expense than CNB or intraoperative frozen specimen evaluation [24, 29].
Summary
A confirmatory histologic diagnosis of metastatic bone disease should be obtained prior to surgical intervention for an osseous abnormality presumptively attributed to metastatic carcinoma. The cost, time, and risks associated with a biopsy are negligible compared to the catastrophic consequences of inadvertently treating a primary bone malignancy as if it were metastatic disease.
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