False positive uptake of metaiodobenzylguanidine in hepatocellular carcinoma

Diffuse Large B-cell Lymphoma: Unexpected Uptake Observed on Cardiac 123I-MIBG Scintigraphy

ABSTRACT

A 77-year-old man with parkinsonism was referred to the department of neurology for further examination. Cardiac 123I-MIBG scintigraphy unexpectedly showed strong uptake in the left shoulder, suggestive of MIBG-avid tumors including paraganglioma. MRI revealed multiple nodules suggestive of lymphoma. A biopsy was performed, which led to the pathological diagnosis of diffuse large B-cell lymphoma. Cardiac MIBG scintigraphy sometimes shows unexpected findings outside the mediastinum. In addition, lymphoma should also be added to the list of differential diagnoses for MIBG-positive tumors.

False-positive 123I-metaiodobenzylguanidine scan in a patient with renal cell carcinoma: A case of chromophobe renal cell carcinoma oncocytic variant with a complicated clinical course

INTRODUCTION

123I-metaiodobenzylguanidine scanning has high sensitivity and specificity for the diagnosis of tumors derived from sympathetic nerves or the adrenal medulla. We report the rare case of a 123I-metaiodobenzylguanidine false-positive renal cell carcinoma.

CASE PRESENTATION

The patient was referred to our hospital with an incidental left renal mass during evaluation for hypertension. An ovarian tumor and prominent ascites were also observed. Serum and urine catecholamine levels were high to suspect a catecholamine-producing tumor of the kidney. 123I-metaiodobenzylguanidine scintigraphy showed increased 123I-metaiodobenzylguanidine intake in the tumor. Laparoscopic radical left nephrectomy was performed. The pathologic diagnosis was an oncocytic variant of chromophobe renal cell carcinoma. No pheochromocytoma features were found.

CONCLUSION

We report the first case of a 123I-metaiodobenzylguanidine false-positive renal cell carcinoma. This case was diagnosed with primary aldosteronism and Meigs' syndrome, which made the clinical course more complicated.

[TWO CASES OF FALSE POSITIVE 123I-MIBG SCINTIGRAPHY FINDINGS OF UPTAKE IN ADRENAL TUMORS]

Case 1 was a 71-year-old female who had been examined by her primary care physician for palpitation and hypertension. Urinary hormone test results revealed elevated urine metanephrine at 0.20 mg/day, urine normetanephrine at 0.45 mg/day and urine noradrenalin at 234.9 μg/day. ¹²³I-MIBG scintigraphy showed uptake in the right suprarenal area, thus she was referred to our department because of pheochromocytoma. She underwent a laparoscopic right adrenalectomy and pathological results led to a diagnosis of adrenocortical adenoma. Case 2 was a 70-year-old female who had been examined at our hospital for hypertension. Blood hormone test results revealed elevated noradrenalin at 0.70 ng/ml. ¹²³I-MIBG scintigraphy showed uptake in the left suprarenal area and she was referred to our department because of pheochromocytoma. She underwent a laparoscopic left adrenalectomy, thus pathological results showed no tumor lesion.

False Positive Radioiodinated Metaiodobenzylguanidine ((123)I-MIBG) Uptake in Undifferentiated Adrenal Malignant Tumor

¹²³I-Metaiodobenzylguanidine (¹²³I-MIBG) scintigraphy is a widely used functional imaging tool with a high degree of sensitivity and specificity in diagnosis of pheochromocytoma. However, rare cases of false positive reactions have been reported. A 67-year-old male patient was admitted with epigastric pain. Abdominal computed tomography (CT) revealed a heterogeneous left adrenal mass 6 cm in diameter; following hormone testing, ¹²³I-MIBG scintigraphy was performed to determine the presence of pheochromocytoma, which confirmed eccentric uptake by a large left adrenal gland mass. Chest CT and PET-CT confirmed metastatic lymphadenopathy; therefore, endobronchial ultrasound transbronchial needle aspiration was performed. Metastatic carcinoma of unknown origin was suspected from a lymph node biopsy, and surgical resection was performed for definitive diagnosis and correction of excess hormonal secretion. A final diagnosis of undifferentiated adrenal malignant tumor was rendered, instead of histologically malignant pheochromocytoma, despite the uptake of ¹²³I-MIBG demonstrated by scintigraphy.

Unusually increased metaiodobenzylguanidine uptake in a gastrointestinal stromal tumor of the stomach

A 70-year-old woman with a submucosal gastric tumor was referred to our hospital for surgical treatment. Upon examination, it was found that she had hypertension, and abdominal computed tomography revealed swelling on both adrenal glands. The patient was examined with gamma camera imaging and iodine-123 metaiodobenzylguanidine (MIBG), because her hypertension was thought to be due to a suspected adrenomedullary tumor. The planar image showed an unexpected abnormal uptake of MIBG in the upper abdomen. On single-photon emission computed tomographic images, the area of abnormal tracer uptake was thought to correspond to the known gastric tumor. The surgical procedure and histological assessments revealed that the gastric tumor was a gastrointestinal stromal tumor (GIST). MIBG can accumulate in GISTs as well as in neuroendocrine tumors of the medulla of the adrenal glands. Although the cause of radiolabeled MIBG uptake in GISTs is uncertain, further studies are necessary to establish the significance of MIBG scintigraphy in GIST imaging.

False-positive accumulation of metaiodobenzylguanidine in a case with acute intermittent porphyria

We report a 36-year-old woman presenting with hypertensive encephalopathy followed by bulbar palsy and quadriplegia. After an extensive screening for secondary causes of hypertension, the patient was suspected of having pheochromocytoma due to increased levels of catecholamines in the plasma and the urine, and positive (131)I-metaiodobenzylguanidine (MIBG) accumulation in the gallbladder. However, MIBG accumulation was not reproducible without any tumors accompanying this accumulation in the gallbladder. A diagnosis of acute intermittent porphyria was finally confirmed based on the characteristic pictures, increased urinary excretion of porphobilinogen, and identification of a heterozygous missense mutation of R173W in the hydroxymethylbilane synthase gene. This case highlights a pitfall in utilizing MIBG to detect a source of excessive catecholamine and also suggests the importance of having a complete clinical history and extensive work-up of any possible differential diagnosis. We also review the potential mechanism by which false-positive MIBG accumulation occurs.

False-positive 123I-metaiodobenzylguanidine (MIBG) scan in a patient with angiomyolipoma; positive MIBG scan does not necessarily indicate the presence of pheochromocytoma

123I-Metaiodobenzylguanidine (123I-MIBG)-accumulation in angiomyolipoma (AML) is demonstrated. A 24-year-old Japanese woman presented with tumors in the right retroperitoneal space. The tumors, which accumulated 123I-MIBG, had been thought to be adrenal pheochromocytoma before surgery. They were removed, and were found to be AML. 123I-MIBG was accumulated in AML. 123I-MIBG-accumulation in AML led to a false-positive diagnosis of adrenal pheochromocytoma. Catecholamine levels had been normal. No chromaffin cells were found in the histological examination of the tumors. MIBG accumulation does not necessarily indicate the presence of pheochromocytoma.

[Uptake of 123I-MIBG in a hepatic hemangioma in the scintigraphic study of an adrenal gland lesion]

A 60 year old symptom free female in whom a lesion in left adrenal gland was found by chance in a CT scan is presented. She also had increased serum and urine catecholamines levels. 123I-MIBG scintigraphy showed a non-physiological uptake in right adrenal gland that is still seen in the delayed image, with normal left gland. MRI confirmed the presence of a mass in the left adrenal gland suggestive of an adenoma and found a lesion in the right hepatic area at the level of the previously seen MIBG image. This lesion was labelled as a hemangioma and would explain the findings of the isotopic study with MIBG. It must be considered as a false positive for phaechromocytoma. The increased catecholamine serum and urine levels were due to drug interactions.