Coaxial Breast Biopsy Device Provides Diagnostic Specimens
Coaxial Breast Biopsy Device Provides Diagnostic Specimens
CHICAGOA simple coaxial breast biopsy tool that can be guided by mammography provides a larger tissue specimen than standard core needle biopsies, causes less bleeding and scarring than surgical biopsy, and carries a smaller price than stereotactically guided biopsy procedures, according to Lincoln Russin, MD, who devised the new biopsy tool. Dr. Russin is a radiologist at Noble Hospital, Westfield, Massachusetts, and associate clinical professor of radiology, Yale University.
The technique offers real potential for significant improvement in breast biopsy technique for women everywhere, Dr. Russin said at the 85th Annual Meeting of the Radiological Society of North America (RSNA). It may put precise, minimally invasive breast biopsy in the realm of the small community hospital or clinic that does not have the resources to purchase stereotactic equipment.
In a pilot study, the device has been used on three patients with microcalcification clusters. One patient had a noninvasive ductal carcinoma; the other two had benign adenosis. In each case, the coaxial breast biopsy tool removed a tissue sample of approximately 1 cc, weighing about 1 g, with an average blood loss of 3 cc. The biopsy system has been patented, Dr. Russin said, but is not yet available commercially.
Problems With Current Methods
The coaxial breast biopsy technique is a response to the problems that exist with current biopsy methods, Dr. Russin said. The conventional hookwire-guided surgical biopsy is overly invasive for making a diagnosis, particularly when 80% of breast lesions are benign, he said. Surgical biopsy provides specimen sizes between 10 g and 30 g, when only 1 g or less is needed. The standard surgical biopsy can also result in scarring and, in some cases, deformity of the breast, he said.
Core needle biopsies have a cancer detection rate of 95%; however, it is difficult, if not impossible, to obtain a biopsy of microcalcifications without stereotactic equipment. Core biopsies using a 14-gauge needle may obtain only 15 mg to 35 mg of tissue per core.
Even if you take 5 or 10 cores, you still may end up with an insufficient sample for pathologic diagnosis, and the patient may need to go to surgical biopsy just for diagnosis, Dr. Russin said.
Newer biopsy methods, such as the Advanced Breast Biopsy Instrument (ABBI) and the vacuum-driven Mammotome, require stereotactic tables, which cost approximately $250,000 and are beyond the economic reach of most small hospitals and clinics, and certainly are not available in the vast majority of medical settings worldwide, he noted.
The ABBI has the potential to completely excise small lesions, but not as currently used, Dr. Russin said. Its most commonly used in the 2 cm model, which excises a cylinder of tissue that is 2 cm in diameter and 10 or 15 cm in length, generally from the subcutaneous tissue down through the lesion to a point far below, he explained. This core of tissue is generally larger than necessary to make a diagnosis, but it is not really large enough to achieve total excision of any lesion.
The coaxial breast biopsy technique uses ordinary mammography to obtain a tissue sample that, Dr. Russin believes, is more satisfactory than surgical, core needle, or newer biopsy methods. It captures 1 g of tissue from the center of a mammographic lesion.
This may be a superior specimen for pathologic analysis because it gives a truer picture of what is going on inside the tumor than the Mammotome, which typically takes a series of 10 small slivers in radial fashion from the point of entry, to end up with an 850-mg specimen, he said. Comparing a bloc of tissue to an equivalent weight of tissue fragments is like comparing an intact map to a pile of map fragments. Tissue architecture is seen better with a larger specimen.
Larger cannulas, as used in the coaxial system, at least theoretically, could totally excise a lesion, he said. The surgeon would advance the cutting cannula through a planar incision down to the spiked collar [see Figures 1 and 2], with the lesion maintained centrally in the path of the cannula. Then, the cannula would make a circular incision around the cancer, to excise a cylinder of tissue with the cancer in the middle, surrounded by a margin of normal tissue. The margin width would be determined by the diameter of the cannula, Dr. Russin said.
The coaxial breast biopsy tool is patterned after the hookwire-localized surgical breast biopsy, but instead of using a flexible wire, it employs a rigid rod with flexible steel anchor hooks. First, a sharp rigid rod is inserted through the lesion, under mammographic guidance, and an introducer tube is advanced over the rod. The sharp rod is then withdrawn.
After mammography confirms that the tube is in the correct position deep to the lesion, the rigid rod with the anchor hooks is inserted. The anchor hooks extend from the end of the tube, become embedded in breast tissue, and stabilize the biopsy device. An etch-mark near the outer end of the rod flags the proper depth of insertion of the cutting cannula.
A microscalpel, which consists of an arc of surgical blade laser-welded to a tube, is passed over the rod to make a slit incision down to the top of the lesion as shown on mammography. A loose-fitting collar with radially welded flexible wire spikes is then inserted to mark the beginning of the target zone (see Figure 1 ). At this point, the breast is removed from the mammogram machine and compressed in tongs (see Figure 2). The original skin incision is spread apart until the surgeon can see the spiked collar.
A cannula/obturator is passed down to the spiked collar, where the biopsy incision begins. The obturator is withdrawn to expose the cutting edge of the cannula. The cutting cannula is advanced until it reaches the anchor hooks, when the etch-mark on the tip of the rod becomes visible.
A snare loop wire then severs the tissue specimen from the surrounding breast, and the specimen is withdrawn with the cannula. The small incision is then closed with sutures.