SURGICAL PATHOLOGY OF ENDOCRINE AND ...

4 G. Moonis and K. Mani
Fig. 6 Parathyroid adenoma
imaging. Technetium-99m
sestamibi scan (a) on a 32-yearold
woman with
hyperparathyroidism
demonstrates a focus of
increased uptake overlying the
upper pole of the thyroid
(arrows), which corresponded to
a hypoechoic lesion in this locale
(arrows) on the corresponding
ultrasound examination (b).
This was a surgically proven
parathyroid adenoma
lesions (Fig. 6a). Initially the agent distribution is proportional
to blood flow. Once intracellular the agent is sequestered
within the mitochondria, especially in overactive
parathyroid gland. The agent reaches maximum activity
inside the thyroid gland within 5 min whereas parathyroid
activity is sustained and washout is delayed allowing for a
double phase study based on the differential washout rate
from the thyroid versus the parathyroid [16–19]. Sensitivity
of 68–95% and specificity of 75–100% have been attributed
to the dual phase technique, particularly in conjunction
with single photon emission tomography (SPECT)[20–24].
On ultrasound (US) the typical parathyroid adenoma is
seen as an oval mass of low echogenicity, which is attributable
to its uniform hypercellularity [25] (Fig. 6b). Preoperative
imaging facilitates minimally invasive surgery as an
alternative to bilateral neck dissection. A combined interpretation
of Tc-99m sestamibi and US results is helpful in
planning targeted exploration [26–28]. Cross sectional imaging
(CT/MRI) is helpful for localizing ectopic adenomas,
particularly in the mediastinum [29, 30] (Fig. 7). This is
especially useful following failed surgery. On CT, these
lesions are well defined and enhance intensely (Fig. 8).
On MRI, these lesions are increased in signal on T2weighted
images, intermediate on T1-weighed images
and demonstrate intense enhancement [8] (Fig. 7). No
imaging modality can differentiate a parathyroid adenoma
from a parathyroid carcinoma.
Carcinoid Tumor
a b
One of the most familiar of the neuroendocrine tumors is
carcinoid tumor (also referred to in later chapters as
neuroendocrine tumor), arising from enterochromaffin
cells, which can occur widely throughout the body.
Most commonly, however, they are found in the gastrointestinal
or bronchopulmonary tracts.
Fig. 7 Ectopic parathyroid adenoma. Axial T2-weighted MR
image of the neck in a 60-year-old female with hyperparathyroidism
not responsive to bilateral parathyroidectomy reveals a round
hyperintense lesion in the right neck parapharyngeal space, which
was surgically proven to be an ectopic PT adenoma (arrows)
Gastrointestinal Carcinoid Tumor
(Neuroendocrine Tumor)
Carcinoid tumors as described in Chapter 12 can affect
the gastrointestinal tract from the esophagus to the rectum,
but are most common in midgut, including the jejunum,
ileum, appendix, and ascending colon [31]. These