Renal Metastasis from Follicular Thyroid Carcinoma Diagnosed by I-131 Whole-body Scan Mimicking Renal Cell Carcinoma on Contrast-Enhanced Computed Tomography

Clinically detectable well-differentiated metastatic thyroid carcinoma to the kidney is rare and should be differentiated from primary renal malignancy. We report a case of renal metastases from follicular thyroid carcinoma (FTC) diagnosed by I-131 whole body scan. Additional features of this case different from previous case reports are solitary renal metastasis on I-131 whole body scan and mimicry of renal cell carcinoma on contrast-enhanced computed tomography.     

FDG positron emission tomographic, radioiodine, and MIBI imaging in a patient with poorly differentiated insular thyroid carcinoma.

Poorly differentiated insular thyroid carcinoma is now classified as a separate entity among other tumors of the thyroid gland. Its histologic pattern and its clinical course are regarded as intermediate between well differentiated and anaplastic thyroid cancer. Insular carcinoma accumulates I-131, but no data exist regarding its fluorodeoxyglucose (FDG) positron emission tomographic (PET) uptake. The authors report F-18 FDG PET, Tc-99m MIBI, and radioiodine imaging features in a 63-year-old patient with metastatic insular thyroid carcinoma. After total thyroidectomy (for poorly differentiated insular carcinoma pT3a), the patient was referred for radioiodine ablation. No signs of recurrence were present until 16 months later, when thyroglobulin levels increased. An I-131 scan showed a single lesion in the right lung, and further radioiodine treatment was administered (cumulative dose [530 mCi], 19,610 MBq I-131). Three years after the initial diagnosis, FDG-PET and Tc-99m MIBI scans were performed within 5 days during thyroxine treatment. After that, thyroxine substitution was withdrawn; 6 weeks later, an I-131 whole-body scan was performed. Both radioiodine and MIBI images showed increased tracer uptake in the known lung lesion. However, FDG PET showed a normal tracer distribution. Magnetic resonance and computed tomographic imaging confirmed a 12-mm lesion in the right upper lobe. These findings support the concept of the "flip-flop phenomenon" in insular thyroid carcinoma, an alternating pattern of metastases with either I-131 or FDG-uptake. Despite poorly differentiated histologic findings, glucose metabolism was not increased in this patient with an insular tumor.     

I-131 accumulation in gastric pull-up simulating pulmonary metastases on total-body scan for thyroid cancer

A follow-up total-body I-131 scan in a patient with follicular thyroid carcinoma demonstrated radionuclide accumulation in the right hemithorax. Originally thought to be pulmonary metastatic thyroid carcinoma, the uptake region proved to be intrathoracic gastric mucosa. The patient had been treated for squamous cell esophageal carcinoma by esophagogastrostomy reconstruction with gastric pull-up. This unusual imaging pattern could have been interpreted as metastatic disease in the absence of complete patient records, an appreciation of normal gastric concentration patterns of I-131, and corroborative imaging study analysis.     

Hyperthyroidism with metastatic follicular thyroid carcinoma

A 70-yr-old woman presented with hyperthyroidism and metastatic follicular carcinoma of the thyroid. The blood level of thyroid stimulating immunoglobulin (TSIg) was elevated. A total thyroidectomy was performed. One month later she remained hyperthyroid. Three weeks after therapy with 218 mCi of I-131 sodium iodide, the patient was euthyroid. Six months after the initial radioiodide therapy, she was again hyperthyroid and was given a second oral treatment dose of I-131 (220 mCi). Five months later, the patient had again become euthyroid. It is likely that initially the woman's metastases were producing sufficient hormone to render her hyperthyroid. After thyroidectomy and two large doses of radioiodide, she has remained euthyroid without having to take exogenous hormone. The blood level of TSIg had become undetectable. Based on this finding, we offer a tentative classification of the causes of hyperthyroidism in patients with thyroid carcinoma.     

I-131 uptake in renal cyst: a false positive result

We present the case of a 60-year old male with a follicular pattern of multifocal invasive papillary thyroid carcinoma who had undergone total thyroidectomy. During post-surgical follow-up with I-131 scan, a I-131 deposit was observed in the upper left hemiabdomen. Due to suspicion that it could be a metastasis, an ultrasound and CT scan were performed, with the subsequent diagnosis of a left simple serous renal cyst. Once confirmed, drainage was performed under ultrasound control, obtaining I-131 in the analysis of its content.     

Substernal thyroid carcinoma detected by 67Ga scan in a patient with normal 131I scan

A patient with a superior mediastinal mass on an admission chest radiograph was initially evaluated by an 131I thyroid scan which failed to demonstrate a substernal thyroid. However, the tomographic 67Ga scan clearly showed an abnormal uptake in the area corresponding to the mass lesion on radiographic examination. Subsequent resection and biopsy of the substernal mass revealed a poorly differentiated follicular carcinoma with foci of anaplastic carcinoma. The differential diagnosis of the anterior mediastinal mass and the usefullness of the tomographic gallium scan are briefly discussed.     

Oncocytoma of the parotid gland causing false-positive result on I-131 whole-body scintigraphy

A 50-year-old patient underwent near-total thyroidectomy in 1997 because of a T?N?M? follicular carcinoma in the right lobe of the thyroid gland, followed by I-131 ablation (3700 MBq). Follow-up of I-131 whole-body scintigraphy after 9 years showed pathologic uptake at the left side of the neck. Histopathologic analyses of the resected specimen suggested a cystic metastasis within the parotid gland, probably originating from thyroid carcinoma. However, the patient had been disease-free for over 9 years and thyroglobulin was undetectable in plasma. Revision of the specimen with complementary immunohistochemical staining revealed histopathologic aspects more typical of oncocytoma.     

Vertebral hemangioma mimicking a metastatic bone lesion in well-differentiated thyroid carcinoma

The authors report a case of abnormal accumulation of I-131 in a thoracic vertebra in a patient with a well-differentiated thyroid carcinoma. The presumptive diagnosis was metastatic bone disease. Further diagnostic work-up confirmed a benign bone lesion. Bone metastasis, when shown on I-131 whole-body scintigraphy, usually supports a change in the staging and therapeutic approach to a patient with thyroid carcinoma. The authors believe that, although an infrequent lesion, the differential diagnosis of abnormal accumulation of I-131 in the body of a vertebra in patients with well-differentiated thyroid carcinoma should raise the possibility of a benign hemangioma. Complete work-up of the suggested bone metastatic lesion should be performed before tumor restaging and I-131 therapy is recommended.     

Bronchoalveolar carcinoma of lung masquerading as iodine avid metastasis in a patient with minimally invasive follicular carcinoma of thyroid

A 52-year-old man with follicular thyroid carcinoma was administered 182 mCi of radioiodine (I-131) a month after total thyroidectomy. Post-therapy scan revealed diffuse uptake of radioiodine in the apical left lung. CT-guided biopsy of this mass revealed mucinous bronchoalveolar carcinoma. Immunohistochemistry for thyroglobulin was negative. An FDG PET scan showed avid uptake in the lung mass. Surgery was ruled out, so he was given chemotherapy, without benefit. The lesion continued to show I-131 uptake even while on daily T3 substitution, suggesting that the mass was thyroid stimulating hormone-independent. Because the mass showed I-131 uptake and chemotherapy was not beneficial, it was decided to treat with I-131. He was continued on T3 substitution therapy and was given 209 mCi of I-131. Follow-up CT scan a few weeks later reported a 1-cm all round reduction of the mass. I-131 scan showed avid tracer uptake in the mass. This case suggests the possibility of this therapeutic option in nonthyroidal tumors that may concentrate radioiodine.     

Technetium-99m tetrofosmin uptake in insular thyroid carcinoma. A comparison with iodine-131

The authors describe a 42-year-old man with insular thyroid carcinoma. In this patient, iodine-131 (I-131) and technetium-99m (Tc-99m) tetrofosmin imaging were performed to investigate residual thyroid tissue and metastatic foci of tumor. Both I-131 and Tc-99m tetrofosmin images showed metastatic foci, but Tc-99m tetrofosmin imaging revealed the lesions better than did the I-131 scan. Tc-99m tetrofosmin imaging does not require withholding of thyroid hormone suppression and can be used for follow-up evaluation of patients with insular thyroid carcinoma.     

Metastatic follicular carcinoma associated with hyperthyroidism

PURPOSE: A 68-year-old man with metastatic follicular thyroid carcinoma had T3 hyperthyroidism. MATERIAL AND METHODS: A bone scan showed intense uptake in the thyroid and multiple areas of increased uptake in the skeleton. Hyperthyroidism persisted after total thyroidectomy. Treatment with I-131 induced a transient state of euthyroidism lasting approximately 9 months. Further tumor growth and relapse of hyperthyroidism eventually occurred and the patient died 25 months after surgery. Molecular and cytogenetic analyses were performed. RESULTS: No mutations were detected of either of the thyrotropin receptor or of the alpha subunit of the stimulatory guanine-nucleotide-binding proteins. Hyperthyroidism was unlikely the result of thyroid-stimulating receptor antibodies. Comparative genomic hybridization analysis showed that the tumor was characterized by multiple chromosomal imbalances. CONCLUSIONS: This is an unusual case of follicular thyroid carcinoma with initial high I-131 uptake by the thyroid and bone metastases and concurrent hyperthyroidism. Despite the increased I-131 uptake in the tumor, I-131 treatment only transiently controlled the hyperthyroidism and had no effect on tumor size. The cause of hyperthyroidism remained unknown. T3 predominance was unlikely the result of type 2 deiodinase overexpression because loss of genetic material was demonstrated at chromosome 14 long arm, where type 2 deiodinase is mapped.     

Medullary thyroid carcinoma: localization of a mediastinal metastasis with I-131 MIBG

An I-131 metaiodobenzylguanidine (MIBG) scan was performed in a patient with a familial history of multiple endocrine neoplasia (MEN) type 2 and recurrent medullary thyroid carcinoma (MTC). The scan revealed a mediastinal metastasis from her MTC and there was also an imaging pattern of bilateral adreno-medullary hyperplasia. Although the literature indicates that I-131-MIBG scanning is not sufficiently sensitive for the detection of MTC, this procedure has proven to be of value in the management of chosen patients with MEN-associated MTC.     

Treatment rationale in thyroid carcinoma. Effect of scan dose

The authors have previously shown that the definition of ablation of thyroid tissue in patients treated with thyroidectomy and radioiodine (I-131) for thyroid carcinoma depends upon the dose of I-131 used to scan the patient. The therapeutic response to I-131 therapy was evaluated in a group of ten differentiated thyroid cancer patients who had a negative 2-mCi (-2 mCi) diagnostic study, but had a positive 10-mCi (+10 mCi) diagnostic study (group 1) during their follow-up evaluation. These results were compared to another group of ten differentiated thyroid cancer patients who received I-131 ablation therapy based on a positive 2-mCi (+2 mCi) I-131 scan (group 2). Six patients in group 1 and eight in group 2 had improvement or ablation of residual tissue based on the 10-mCi scan following therapy. The difference in response between the two groups was not statistically significant (P = 0.63) by two-tailed Fisher's exact test, indicating that even patients with -2-mCi, but +10-mCi scans may respond to I-131 therapy. Whether the large dose therapy makes any impact on the clinical outcome has not been answered by this study.     

False-positive result of a total-body scan caused by benign thyroidal tissue after I-131 ablation

This case report illustrates a false-positive result of an I-131 total-body scan caused by abnormal, noncancerous thyroid tissue. A 39-year-old woman underwent an open biopsy and thyroidectomy for a papillary thyroid carcinoma. She was treated by ablation with 150.8 mCi I-131. A follow-up total-body scan revealed a solitary focus of increased activity near the midline at the upper border of the larynx that was subsequently excised. Histologic analysis indicated a fragment of thyroid tissue with chronic inflammation, fibrosis, and squamous metaplasia. No evidence of thyroid carcinoma was present. Hypofunctioning or nonfunctioning residual tissue within the thyroglossal duct may have been suppressed under euthyroid conditions, protecting it from ablation. This tissue may have become stimulated by the high thyroid-stimulating hormone levels, accumulating I-131 and producing a false-positive result of the scan.     

Follicular thyroid carcinoma presenting with multiple skull metastases on CT and MRI: A case report and literature review

Although the incidence of thyroid carcinoma has increased in recent years, follicular thyroid carcinoma with bone metastasis as the first symptom remains rare. Here, we report a case of occult follicular thyroid carcinoma in a 65-year-old female patient admitted to hospital with cerebrovascular disease. Computed tomography findings suggested a diagnosis of meningioma; however, magnetic resonance imaging results showed multiple skull bone destruction with soft tissue masses on the left side of the skull. After surgical resection, the pathology results revealed skull metastasis of follicular thyroid carcinoma. We present this case not only because of the diagnostic challenge it posed, but also because the patient had multiple skull metastases from follicular thyroid carcinoma.     

Compare FDG-PET and Tc-99m tetrofosmin SPECT to detect metastatic thyroid carcinoma

RATIONALE AND OBJECTIVES: The effectiveness of 18-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) and technetium-99m tetrofosmin (Tc-99m TF) single photon emission computed tomography (SPECT) of neck and chest was evaluated to detect metastatic lesions in well-differentiated thyroid carcinoma after nearly total thyroidectomy and radioiodine (I-131) treatment who present with elevated serum human thyroglobulin levels but negative I-131 whole body scan. MATERIALS AND METHODS: Twenty-three patients with differentiated thyroid carcinoma who underwent nearly total thyroidectomy and I-131 treatments were included in this study. RESULTS: All of the 23 patients had negative I-131 whole body scan and elevated human thyroglobulin levels under thyroid-stimulating hormone stimulation. Metastatic lesions were detected by FDG-PET in 20 patients, while Tc-99m TF SPECT revealed metastatic lesions in only 11 of the 20 patients. Both FDG-PET and Tc-99m TF SPECT failed to demonstrate miliary pulmonary metastases in two of the remaining three patients. The other patient did not show any lesion on FDG-PET, Tc-99m TF SPECT, chest computed tomography, or other imaging techniques. CONCLUSION: This study demonstrated that FDG-PET is more sensitive than Tc-99m TF SPECT to detect metastatic lesions in differentiated thyroid carcinoma with elevated human thyroglobulin but negative I-131 whole body scan. However, miliary pulmonary metastases could be missed by the both techniques.     

Brain metastases with exceptional features from papillary thyroid carcinoma: report of three cases

We present three papillary thyroid carcinoma PTC patients with brain metastases who are unusual in many aspects. The first case is a unique 3mm papillary thyroid microcarcinoma (PTMC) patient with metastases to the cerebrum and lung. The solitary cerebral lesion was identified by iodine-131 whole- body scan ((131)I-WBS) and (131)I single photon emission tomography/computed tomography (SPET/CT). Almost complete response achieved after radiosurgery. The second case is a unique PTC patient with coexistent (131)I-negative cerebrum, adrenal gland and ilium metastases, which were identified by (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging (MRI). Partial response achieved after radiosurgery. The third case is a patient with an incident solitary cystic cerebellar mass as a primary presentation of follicular variant of PTC and absent other distant metastases. In conclusion, widespread metastases from small PTMC may occur. Concomitant brain and adrenal metastases may occur in a same PTC patient. Brain metastasis may present as a cystic lesion.     

False-positive iodine-131 body scan caused by a large renal cyst

Focal I-131 accumulation is generally a reliable indicator of functioning thyroid tissue or a differentiated thyroid cancer metastasis. Normal accumulation of activity may be seen in areas such as the intestinal tract, liver, and salivary glands. This report describes a patient with significant accumulation of I-131 in the right upper quadrant of the abdomen. The abnormality, first thought to represent metastatic thyroid carcinoma, was subsequently proven to be accumulation within a large renal cyst.     

Preoperative scintigraphic visualization of an orbital metastasis before identification of carcinoma in a nonfunctioning thyroid nodule

Preoperative accumulation of Tc-99m pertechnetate and radioiodine in metastases of well-differentiated thyroid carcinoma is uncommon. The authors report the case of a 51-year-old woman with follicular thyroid carcinoma revealed by a right orbital metastasis. I-131 scintigraphy performed before thyroidectomy showed intense uptake in an orbital metastasis despite the presence of an intact thyroid gland.     

Gamma probe-guided resection and scanning with TC-99m MIBI of a local recurrence of follicular thyroid carcinoma

A 30-year-old woman underwent two operations for multinodular goiter and follicular thyroid carcinoma. The residual thyroid tissue was ablated by I-131 therapy. After 7 years of follow-up, Tc-99m MIBI and I-131 scintigraphy were performed, because her serum thyroglobulin level was much higher compared with the control analysis performed in the sixth year. Tc-99m MIBI showed pathologic accumulation, which could be consistent with a local recurrence, whereas the results of I-131 scintigraphy were negative. The locally recurring follicular thyroid carcinoma was resected using a gamma probe and Tc-99m MIBI. The thyroglobulin level decreased to a normal level after surgery. This case shows that the intraoperative use of a gamma probe with Tc-99m MIBI allows localization of recurrent thyroid tissue in the scarred area in patients with increased radionuclide accumulation, and scanning of the affected area using the gamma probe may be helpful in determining whether resection is complete.