Diagnostic ultrasound ( PDFDrive )

750 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
A
B
6 cm
2 cm
C
D
FIG. 20.20 Comparison of Surgical Procedures for Removal of Parathyroid Adenoma. (A) Intraoperative photograph during bilateral neck
dissection for parathyroidectomy. The thyroid gland (T) is retracted back and a parathyroid adenoma (arrow) exposed. (B) Corresponding 6-cm
“collar” incision with a surgical drain. (C) Intraoperative photograph during minimally invasive surgery uses a much smaller incision. Parathyroid
adenoma is exposed adjacent to the thyroid (T). (D) Minimally invasive surgical incision, approximately 2 cm. (Courtesy of Geoffrey B. Thompson,
MD, Mayo Clinic, Rochester, Minn.)
PERCUTANEOUS BIOPSY
Sonographically guided percutaneous FNA biopsy can be used
for preoperative conirmation of suspected abnormal parathyroid
glands in selected cases, particularly in the candidate for reoperation.
59,60,94,96-102,136 his technique can decrease the false-positive
rate and increase the speciicity of sonography by permitting the
reliable diferentiation of parathyroid adenomas from other
pathologic structures, such as thyroid nodules and cervical lymph
nodes. In addition to its value to the surgeon, a positive biopsy
may reassure the reluctant reoperative patient. FNA biopsy is
also generally obtained for diagnostic conirmation before
percutaneously injected ethanol ablation of a suspected abnormal
gland.
If the suspected parathyroid adenoma is in a location remote
from the thyroid gland, the main diferential diagnostic consideration
is a lymph node. Percutaneous biopsy is performed by
using a standard noncutting 25- or 27-gauge needle to obtain
aspirates that contain either parathyroid cells or lymphocytes
(Fig. 20.23, Videos 20.17 and 20.18). he aspirate must also be
analyzed for PTH because elevated levels indicate the presence
of parathyroid tissue, even if the cytologic results are
inconclusive. 19,96-99 Ater the aspirated material is expelled onto
a slide for cytologic review, the residual sample in the needle
hub is rinsed with a tiny amount of sterile saline, emptied into
a tube, and placed on ice. his is repeated for each aspirate,
diluting the sample for PTH assay into a total volume of 1 to
1.5 mL. Alternatively, three to four aspirates may be expelled
and rinsed directly into a tube containing 1 to 1.5 mL of sterile
saline, then placed on ice. When performed in this manner,
positive aspirate assays yield PTH levels markedly higher than
that of normal serum levels, and typically much higher than the
patient’s own inappropriately elevated serum PTH levels. If the
suspected parathyroid adenoma lies adjacent to the thyroid, FNA
biopsy may be necessary to diferentiate parathyroid and thyroid
tissue. hese aspirates should also be analyzed for PTH because
parathyroid and thyroid tissue can be very diicult to diferentiate
by cytology. 19,96-99 In addition, thyroid tissue sometimes must be
traversed to access a parathyroid adenoma, causing possible
sample contamination with thyroid cells. 19 A histologic specimen
obtained with a small-caliber (20- to 22-gauge) cutting needle
may provide more cellular material for analysis but usually is
unnecessary if PTH assay is performed. In addition, the possibility
of postbiopsy periglandular ibrosis complicating subsequent