Octreotide uptake in parathyroid adenoma

GIANT MEDIASTINAL PARATHYROID ADENOMAS AND MULTIPLE ENDOCRINE NEOPLASIA TYPE 1: A DIAGNOSTIC CONUNDRUM

CONTEXT

Giant parathyroid adenoma (GPA) is a rare entity that is rarer with Multiple endocrine neoplasia type 1 (MEN1) syndrome.

OBJECTIVES

Describe the clinical presentation, diagnostic difficulties, and management strategy for GPA in MEN1.

METHODS

We searched Pubmed, SCOPUS and EMBASE for GPA in MEN1 for GPA in association with MEN1. Hereby, we describe index case of largest ever reported GPA.

RESULTS

We identified 7 cases of GPA reported till date in association with MEN1. The mean adenoma weight was 7.1 gram. The index case is largest-ever reported GPA (weight 97 gram) in MEN1 presenting with compressive symptoms and mediastinal mass. Incidentally, she was found to have hypercalcemia with increased parathyroid hormone, suggesting primary hyperparathyroidism. The possibilities of an ectopic parathyroid tumor and thymic carcinoid were considered. She also had acromegaloid features, and was found to have a sellar tumor. Subsequently, MENIN gene mutation was identified confirming MEN1 syndrome. Patient underwent trans-sternal excision of the mass weighing 97 grams and confirmed as parathyroid adenoma on histopathologic examination.

CONCLUSION

Despite rarity of ectopic mediastinal parathyroid tumors, calcium profile should be considered as part of work-up of considering varied etiologies of anterior mediastinal mass.

Mediastinal Cystic Parathyroid Adenoma Diagnosed by Somatostatin Receptor Scintigraphy

A 71-year-old man complained of nausea and loss of appetite for eight months prior to admission. He was transported to a hospital with disorientation and diagnosed with primary hyperparathyroidism by laboratory examinations. However, ultrasonography, computed tomography, and technetium-99m labeled methoxyisobutyl isonitrile (^99mTc-MIBI) with single-photon emission computed tomography did not yield definite results. In contrast, somatostatin receptor scintigraphy successfully identified the lesion responsible for the over-secretion of parathyroid hormone within the middle mediastinum. The tumor was successfully resected by surgery, and a histopathological analysis confirmed the parathyroid adenoma nature of the tumor.

Somatostatin receptor expression in parathyroid neoplasms

INTRODUCTION

Parathyroid carcinoma represents a rare cause of primary hyperparathyroidism. Distinguishing carcinoma from the benign tumors underlying primary hyperparathyroidism remains challenging. The diagnostic criteria for parathyroid carcinoma are local and/or metastatic spreading. Atypical parathyroid adenomas share other histological features with carcinomas but lack invasive growth. Somatostatin receptors are commonly expressed in different neuroendocrine tumors, but whether this also holds for parathyroid tumors remains unknown.

AIM

Our aim is to examine the immunohistochemical expression of somatostatin receptor 1-5 in parathyroid typical adenomas, atypical adenomas and carcinomas.

METHODS

We used a tissue microarray construct from a nationwide cohort of parathyroid carcinomas (n = 32), age- and gender-matched typical parathyroid adenomas (n = 72) and atypical parathyroid adenomas (n = 27) for immunohistochemistry of somatostatin receptor subtypes 1-5. We separately assessed cytoplasmic, membrane and nuclear expression and also investigated the associations with histological, biochemical and clinical characteristics.

RESULTS

All parathyroid tumor subgroups expressed somatostatin receptors, although membrane expression appeared negligible. Except for somatostatin receptor 1, expression patterns differed between the three tumor types. Adenomas exhibited the weakest and carcinomas the strongest expression of somatostatin receptor 2, 3, 4 and 5. We observed the largest difference for cytoplasmic somatostatin receptor 5 expression.

CONCLUSIONS

Parathyroid adenomas, atypical adenomas and carcinomas all express somatostatin receptor subtypes 1-5. Somatostatin receptor 5 may serve as a potential tumor marker for malignancy. Studies exploring the role of somatostatin receptor imaging and receptor-specific therapies in patients with parathyroid carcinomas are needed.

Visualization of Gallbladder with In-111 Octreotide Scan

A 54-year-old woman underwent octreotide scintigraphy for evaluation of neuroendocrine tumor recurrence. The images demonstrated unusual uptake in gallbladder area in addition to physiologic uptake at other tissues. Whole-body planar and SPECT imaging were repeated after fatty meal ingestion at 28 hours in order to figure out whether this activity was physiologic or not. Since the unusual uptake in the gallbladder was still detected at these images, additional images were obtained 72 hours after radionuclide injection. The activity in the gallbladder disappeared at these images revealing the physiologic nature of this unusual accumulation.