Keywords
18F-fluorocholine -
18F-fluorodeoxyglucose - positron emission tomography and computed tomography - recurrent
parathyroid carcinoma
Introduction
Parathyroid carcinoma (PTC) – a rare cause of primary hyperparathyroidism requires
complete resection of primary disease though it has a tendency of loco-regional/distant
recurrence.18 F-fluorodeoxyglucose (FDG) positron emission tomography and computed
tomography (PET/CT) has shown its utility in initial staging and restaging of PTC.[1],[2]18 F-fluorocholine (FCH) PET/CT has shown encouraging results in preoperative localization
of parathyroid adenoma,[3],[4] but its utility in PTC is limited to a case report.[5] To the best of our knowledge, this is the second case report, where FCH PET/CT has
shown the complimentary role along with FDG PET/CT scan in the evaluation of recurrent
disease in a patient with recurrent PTC.
Case Report
A 56-year-old female with elevated serum intact parathyroid hormone (PTH) (3414 pg/ml,
normal: 10–65) and calcium levels (12.6 mg/dl, normal: 8.8–10.5) underwent parathyroid
surgery a year back for suspicious parathyroid adenoma. The histopathology revealed
it as parathyroid cancer (high Ki 67 index, 50%) with vascular and capsular invasion.
The patient declined for redo surgery at that time and presented with left-sided neck
swelling, elevated PTH (1027 pg/ml, normal 10–65) and serum calcium levels: (12 mg/dl,
normal 8.8–10.5) on follow-up at 1 year later. The serum alkaline phosphatase and
creatinine were raised with low serum phosphate levels. The patient underwent technetium-99m-labelled
methoxyisobutyl isonitrile (MIBI) dual-phase scintigraphy [Figure 1a] and [Figure 1b] and FCH PET/CT [Figure 1c], [Figure 1d],[Figure 1e],[Figure 1f],[Figure 1g],[Figure 1h] and showed tracer-avid multiple left levels III-IV cervical and the highest mediastinal
lymph nodes suggestive of disease recurrence at the loco-regional site.
Figure 1 Tc-99m methoxyisobutyl isonitrile dual phase scintigraphy at 10 min (early) and 2
h (delayed) showing tracer-avid lesion in the left neck (a and b). 18F-fluorocholine
positron emission tomography and computed tomography maximal intensity projection,
cross-sectional computed tomography and fused images for recurrent disease evaluation,
showing tracer-avid multiple left cervical lymph nodes (c-h)
She subsequently underwent left hemithyroidectomy and modified radical neck dissection.
The surgical resected specimen showed PTC infiltrating into adjacent soft tissue and
skeletal muscle with multiple lymph nodes metastases on histopathology. She developed
breathlessness and pain in the neck after 8 months of the second surgery. She was
again evaluated with biochemical parameters and imaging with chest X-ray, FDG, and
FCH PET/CT. The chest X-ray showed multiple round soft-tissue densities in bilateral
lung fields. The whole-body FDG PET/CT and FCH PET/CT studies [Figure 2a]-h] revealed intensely FDG-avid (maximum standardized uptake value (SUVmax) ~13.1) and moderately choline-avid (SUVmax ~ 4.7) multiple parenchymal and pleural-based lung nodules and mediastinal lymph
nodes. An additional choline-avid (SUVmax 6.5) and non-FDG-avid lesion in the left parasellar location was also noted, which
was suggestive of meningioma on magnetic resonance imaging brain. However, patient
again refused for any intervention for the left parasellar lesion. The patient was
managed on symptomatic treatment, and she passed away after being alive for 2 years
from the date of her first surgery.
Figure 2
18F-fluorodeoxyglucose positron emission tomography and computed tomography and 18F-fluorocholine
positron emission tomography and computed tomography maximal intensity projection,
cross-sectional computed tomography and fused images showing intensely 18F-fluorodeoxyglucose-avid (standardized uptake value maximum ~13.1) and moderately
choline-avid (standardized uptake value maximum ~4.7) multiple parenchymal and pleural-based
lung nodules and mediastinal lymph nodes (arrows in figures a, c, e, g and h). A choline-avid
(standardized uptake value maximum 6.5) and non-18F-fluorodeoxyglucose-avid lesion in the left parasellar location (arrows in figures
b, d and f) MIP: Maximal intensity projection
Discussion
The patients of PTC usually present with palpable neck mass, highly elevated PTH,
and calcium levels. One-third of the patients may have regional lymph node involvement
and metastatic lung, liver, and bone disease and the recurrence of PTC is seen in
around 49%–60% of cases.[1],[6] PTC is difficult to diagnose before surgery and usually confirmed on histopathological
examination. MIBI scintigraphy cannot differentiate between benign and malignant parathyroid
lesions though it has been utilized in localizing the primary and metastatic PTC.[7] FDG PET/CT has demonstrated to be a valuable imaging modality for the evaluation
of PTC regarding tumor metabolism, the extent of the disease and the recurrence at
unusual sites, long after primary treatment where conventional imaging failed in picking
the disease. The primary disease and metastatic sites have shown significant FDG avidity.
The increased SUV value generally indicates the aggressive behavior of the tumor and
poor prognosis.[2],[8],[9] In the index case, the preoperative MIBI showed tracer-avid left inferior parathyroid
lesion followed by postoperative imaging done with MIBI and FCH studies at 1 year
showed intense tracer uptake in the recurrent primary lesion, cervical and mediastinal
nodes. However, the FDG and FCH imaging performed after a period of 8 months following
second surgery showed high FDG and low choline uptake in the mediastinal lymph nodes
and lung nodules. The reason for the divergent avidity of two tracers probably could
be that the recurrent disease had de-differentiated by that time. The choline positive
and FDG negative left parasellar lesion was suggestive of meningioma. Similarly, in
a study of 300 patients of prostate cancer submitted for FCH PET/CT scanning for staging
or restaging, six patients showed additional focal FCH uptake in meningiomas.[10]
FCH PET/CT has shown promising role in the preoperative localization of parathyroid
adenoma,[3],[4] but its role in PTC is limited to a case report where additional metastatic lesions
were detected both by FCH and FDG PET/CT in treated patient of PTC emphasizing the
complementary role of two imaging techniques. The authors postulated that difference
in tumor differentiation and proliferation might have led to discordance in FCH and
FDG uptake in metastatic lesions.[5] Our case had shown the intense cervical lymph nodal FCH uptake at first recurrence,
but moderate FCH and intense FDG avidity in metastatic pulmonary and mediastinal nodal
disease in the subsequent recurrence with the possibility of tumor de-differentiation
during that interval. The FCH PET/CT may have a complementary role in addition to
FDG PET/CT in staging or restaging of PTC in demonstrating the location and extent
of the recurrent disease for further management. The role of FCH PET/CT needs to be
explored in PTC work-up.
FCH PFCH PET/CT as an imaging modality may have an adjunctive role in patients presenting
with parathyroid cancer in staging and restaging since this rare entity has high loco-regional
and distant recurrence of the disease.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form, the patient has given her consent for her images and other clinical information
to be reported in the journal. The patient understand that names and initials will
not be published and due efforts will be made to conceal identity, but anonymity cannot
be guaranteed.
