[Diagnostic value of bilateral inferior petrosal sinus sampling in various modifications and methods of radiation and radionuclide imaging in the diagnosis and differential diagnosis of ACTH-dependent endogenous hypercortisolism]

AIM

To analyze the diagnostic performance of bilateral inferior petrosal sinus sampling (BIPSS) with desmopressin as a stimulation agent and prolactin measurements to control catheter position with or without the ACTH/prolactin normalized ratio calculation in the differential diagnosis of ACTH-dependent endogenous hypercortisolism, and the diagnostics performance of ectopic ACTH-syndrome (EAS) visualization.

MATERIALS AND METHODS

A single-center diagnostic study with a retrospective analysis of the data was carried out. The study included patients with ACTH-dependent endogenous hypercorticism with no visualization of pituitary adenoma on MRI or adenoma sizes less than 6 mm. All patients underwent BIPSS with and without calculation of the ACTH/prolactin normalized ratio. Visualization of an EAS included pituitary MRI (to exclude EAS), whole-body CT scan with contrast, and somatostatin receptor scintigraphy with 99mTc-Tectrotide and CT (99mTc-Tectrotide SPECT). The final verification was based on immunohistochemical confirmation of the tumor or stable remission of Cushing's disease (CD) after surgical treatment. Statistical data processing was carried out by using IBM SPSS Statistics 23. Confidence intervals were calculated using the JavaStat online calculator.

RESULTS

230 BIPSS were performed in 228 patients (166 women, 62 men), of which 178 patients were verified as CD and 50 cases were EAS of various localization. The effectiveness of catheterization of petrosal sinuses was 96.9%. The sensitivity of BIPSS without ACTH/prolactin ratio calculation (n=70) was 95.9% (95% CI 86.3-98.9), specificity was 92% (95% CI 75.0-97.8), for the BIPSS with additional determination of ACTH/prolactin-normalized ratio (n=51) - 97.3% (95% CI 86.2-99.5) and 93.8% (95% CI 71.7-98.9), respectively. The use of the MRI method for this sample of patients had a sensitivity of 60.2% (95% CI 52.6-67.5), specificity of 59.2% (95% CI 44.2-73.0), the total body CT with contrast has a sensitivity of 74% (95% CI 59.7-85.4), specificity of 100% (95% CI 97.95-100). The diagnostic accuracy for 99mTc-Tectrotide SPECT in NET visualization has a sensitivity of 73.3% (95% CI 44.9-92.2), specificity of 100% (95% CI 95.3-100).

CONCLUSION

BIPSS with desmopressin stimulation and prolactin measurements to control catheter position, as well as the additional calculation of the ACTH/prolactin-normalized ratio, is an optimal method for the differential diagnosis of EAS. Patients who are identified an EAS on BIPSS may be further referred for 99mTc-Tectrotide SPECT and CT for tumor visualization.

Ectopic sphenoidal ACTH-secreting adenoma revealed by 11C Methionine PET scan: case report

BACKGROUND

Ectopic ACTH pituitary adenomas (EAPA), located outside the sella turcica and deriving from cellular remnants of Rathke's pouch are a very rare cause of Cushing's syndrome (CS). The diagnosis is often difficult and delayed, even after comprehensive work-up. To our knowledge, we report for the first time an ectopic corticotroph tumor of the posterior wall of the sphenoid sinus, leading to false positive results of bilateral inferior petrosal sinus sampling (BIPPS) and which was finally localized by a co-registered¹¹ C Methionine PET/MR imaging.

CASE PRESENTATION

A 48-year-old woman was referred for a high clinical suspicion of ACTH-dependent CS. Biological testing comprising low dose dexamethasone suppression and CRH stimulation tests were indicative of pituitary Cushing's disease, but comprehensive pituitary MRI did not reveal any pituitary adenoma. BIPSS confirmed however a central origin of ACTH secretion (central-to-peripheral ACTH ratio > 100) and revealed a significant right-to-left gradient (6.2), leading to a first right-sided exploratory hypophysectomy, that did not cure the patient. BIPSS images were reviewed and revealed preferential drainage of the left pituitary to the right petrosal sinus, leading us to a left sided exploratory hypophysectomy, which was again unsuccessful. A¹¹ C Methionine PET/MRI was performed and revealed a hypermetabolic lesion adjacent to the posterior wall of the sphenoidal sinus. After surgical resection, this polypoid mass was identified as an ectopic ATCH-secreting pituitary adenoma expressing ACTH and T-Pit and complete remission of hypercortisolism was observed.

CONCLUSIONS

In conclusion, we report a case of ACTH-dependent Cushing's syndrome, caused by an ectopic corticotroph adenoma located in the sphenoidal sinus, which perfectly mimicked the biological features of a classical pituitary ACTH adenoma on a comprehensive hormonal evaluation including BIPPS, and the features of a benign naso-sinusal polyp at MRI. We report for the first time a key role of¹¹ C Methionine PET co-registered to high resolution MRI for localizing ectopic adenomas, efficiently guiding surgical removal and leading to complete remission of hypercortisolism.

A rare case of ectopic ACTH syndrome with rhabdomyolysis

BACKGROUND

Manifestations of hypokalaemia in ectopic adrenocorticotropic hormonesyndrome(EAS) vary from mild muscle weakness to life-threatening arrhythmia. Herein, we present a rare case of EAS with concomitant rhabdomyolysis(RM) as a result of intractable hypokalaemia.

CASE PRESENTATION

A 64-year-old man was admitted for limb weakness and facial hyperpigmentation for 2 weeks. Lab tests revealed intractable hypokalaemia (lowest at 1.8 mmol/L) and metabolic alkalosis. The diagnosis of RM was based on a creatine kinase(CK)level of 5 times the upper limit. The elevated CK and myohemoglobin (Mb) levels returned to within the normal range after the alleviation of hypokalaemia. The patient was diagnosed with ACTH-dependent Cushing's syndrome (CS) based on unsuppressed serum cortisol after a low-dose dexamethasone suppression test(LDDST) and remarkably elevated ACTH levels. The diagnosis of EAS was made based on the results of a high-dose dexamethasone suppression test(HDDST) and bilateral inferior petrosal sinus sampling(BIPSS). Multiple lymph nodes in the left supraclavicular fossa, right root of neck, mediastinum and bilateral hili of the lung were found with abnormal uptake of ⁶⁸Ga-DOTA-NOC. Mediastinoscopic lymph node biopsy was performed. The pathological diagnosis was small-cell and large-cell neuroendocrine carcinoma with positive ACTH staining. The patient was prescribed mifepristone and received one cycle of chemotherapy. The patient could not tolerate subsequent chemotherapy and died of dyscrasia.

CONCLUSIONS

RM is a rare complication of EAS with insidious onset and atypical clinical manifestations. Serum potassium levels should be vigilantly monitored to avoid RM in EAS.

Case Report: Three Rare Cases of Ectopic ACTH Syndrome Caused by Adrenal Medullary Hyperplasia

Ectopic ACTH syndrome (EAS) accounts for 10-20% of endogenous Cushing's syndrome (CS). Hardly any cases of adrenal medullary hyperplasia have been reported to ectopically secrete adrenocorticotropic hormone (ACTH). Here we describe a series of three patients with hypercortisolism secondary to ectopic production of ACTH from adrenal medulla. Cushingoid features were absent in case 1 but evident in the other two cases. Marked hypokalemia was found in all three patients, but hyperglycemia and osteoporosis were present only in case 2. All three patients showed significantly elevated serum cortisol and 24-h urinary cortisol levels. The ACTH levels ranged from 19.8 to 103.0pmol/L, favoring ACTH-dependent Cushing's syndrome. Results of bilateral inferior petrosal sinus sampling (BIPSS) for case 1 and case 3 confirmed ectopic origin of ACTH. The extremely high level of ACTH and failure to suppress cortisol with high dose dexamethasone suppression test (HDDST) suggested EAS for patient 2. However, image studies failed to identify the source of ACTH secretion. Bilateral adrenalectomy was performed for rapid control of hypercortisolism. After surgery, cushingoid features gradually disappeared for case 2 and case 3. Blood pressure, blood glucose and potassium levels returned to normal ranges without medication for case 2. The level of serum potassium also normalized without any supplementation for case 1 and case 3. The ACTH levels of all three patients significantly decreased 3-6 months after surgery. Histopathology revealed bilateral adrenal medullary hyperplasia and immunostaining showed positive ACTH staining located in adrenal medulla cells. In summary, our case series reveals the adrenal medulla to be a site of ectopic ACTH secretion. Adrenal medulla-originated EAS makes the differential diagnosis of ACTH-dependent Cushing's syndrome much more difficult. Control of the hypercortisolism is mandatory for such patients.

Case Report: A Challenging Localization of a Pulmonary Ectopic ACTH-Secreting Tumor in a Patient With Severe Cushing's Syndrome

BACKGROUND

Ectopic adrenocorticotropic syndrome (EAS) is a rare cause of endogenous ACTH-dependent Cushing's syndrome, usually associated with severe hypercortisolism as well as comorbidities. Tumor detection is still a challenge and often requires several imaging procedures. In this report, we describe a case of an ectopic ACTH secretion with a misleading localization of the responsible tumor due to a concomitant rectal carcinoma.

CASE PRESENTATION

A 49-year-old man was referred to our Endocrinology Unit due to suspicion of Cushing's syndrome. His medical history included metastatic rectal adenocarcinoma, diagnosed 5 years ago and treated with adjuvant chemotherapy, radiotherapy and surgical resection. During follow-up, a thoracic computed tomography scan revealed two pulmonary nodules located in the superior and middle lobes of the right lung with a diameter of 5 and 10 mm, respectively. However, these nodules remained radiologically stable thereafter and were not considered relevant. All biochemical tests were suggestive of EAS (basal ACTH levels: 88.2 ng/L, nv 0-46; basal cortisol levels: 44.2 µg/dl, nv 4.8-19.5; negative response to CRH test and high dose dexamethasone suppression test) and radiological localization of the ectopic ACTH-secreting tumor was scheduled. The CT scan revealed a dimensional increase of the right superior lung nodule (from 5 to 12 mm). [⁶⁸Ga]-DOTA-TOC PET/CT scan was negative, while [¹⁸F]-FDG-PET/CT showed a tracer accumulation in the superior nodule. After a multidisciplinary consultation, the patient underwent thoracic surgery that started with two atypical wedge resections of nodules. Frozen section analyses showed a neuroendocrine tumor on the right middle lobe nodule and a metastatic colorectal adenocarcinoma on the superior lesion. Then, a right superior nodulectomy and a right middle lobectomy with mediastinal lymphadenectomy were performed. The final histopathological examination confirmed a typical carcinoid tumor, strongly positive for ACTH. A post-surgical follow-up showed a persistent remission of Cushing's syndrome.

CONCLUSIONS

The present report describes a case of severe hypercortisolism due to EAS not detected by functional imaging methods, in which the localization of ACTH ectopic origin was puzzled by a concomitant metastatic rectal carcinoma. The multidisciplinary approach was crucial for the management of this rare disease.

ECTOPIC ACTH SECRETION WITH CONCOMITANT HYPERAMYLASEMIA IN A PATIENT WITH SMALL CELL LUNG CARCINOMA: CASE REPORT

Histologically confirmed small cell lung cancer associated with Cushing's syndrome and elevated amylase is rarely described in the literature. We present a case of a 63-year-old patient admitted to cardiology department due to shortness of breath, exhaustion, palpitations and nausea. Elevated values of troponin and electrocardiography suggested that he could have acute coronary syndrome. According to the radiologist's opinion, plane lung radiography was normal. Elevated level of amylase was found in both serum (3802 U/L, normal range 28-100) and urine (12012 U/L, normal range 0-450 U/L), as well as elevated sodium (156 mmol/L, normal range 137-147 mmol/L), hyperglycemia (12 mmol/L, normal range 3.8-6.1 mmol/L) and lowered serum potassium (1.7 mmol/L, normal range 3.5-5.3 mmol/L). Computerized tomography (CT) of the abdomen revealed a tumor of the left adrenal gland and enlargement of the right adrenal gland with normal structure of the pancreas. During hospitalization, the patient had blood while coughing and CT scan of the lungs showed a tumor 48x38x51 mm in size localized in the laterobasal segment of the left lung with mediastinal lymphadenopathy. He also had bilateral pleural effusions with signs of pulmonary embolism, which explained elevated troponin values. Biopsy confirmed microcellular lung carcinoma and tumor cells were diffusely positive for TTF-1 and focally for CK7, expressing markers of neuroendocrine differentiation (chromogranin +++, synaptophysin +++, NSE ++). Since neuroendocrine tumor was confirmed and the patient had low potassium and high glucose, hypercortisolism was suspected. High morning cortisol (1784 mmol/L, normal range 171-536) and unsuppressed ACTH (214 pg/L, < 60), as well as a high level of chromogranin (1339 µg/L, < 65) were determined. During hospital stay, the patient developed heart and respiratory failure and died in the second week of hospitalization.

PET imaging in ectopic Cushing syndrome: a systematic review

Cushing syndrome due to endogenous hypercortisolism may cause significant morbidity and mortality. The source of excess cortisol may be adrenal, pituitary, or ectopic. Ectopic Cushing syndrome is sometimes difficult to localize on conventional imaging like CT and MRI. After performing a multilevel thoracoabdominal imaging with CT, the evidence regarding the use of radiotracers for PET imaging is unclear due to significant molecular and etiological heterogeneity of potential causes of ectopic Cushing's syndrome. In our systematic review of literature, it appears that GalLium-based (Ga68) somatostatin receptor analogs have better sensitivity in diagnosis of bronchial carcinoids causing Cushing syndrome and FDG PET appears superior for small-cell lung cancers and other aggressive tumors. Further large-scale studies are needed to identify the best PET tracer for this condition.

A role for 11C-methionine PET imaging in ACTH-dependent Cushing's syndrome

OBJECTIVE

We report our experience of functional imaging with (11)C-methionine positron emission tomography-computed tomography (PET-CT) co-registered with 3D gradient echo (spoiled gradient recalled (SPGR)) magnetic resonance imaging (MRI) in the investigation of ACTH-dependent Cushing's syndrome.

DESIGN

Twenty patients with i) de novo Cushing's disease (CD, n=10), ii) residual or recurrent hypercortisolism following first pituitary surgery (±radiotherapy; n=8) or iii) ectopic Cushing's syndrome (n=2) were referred to our centre for functional imaging studies between 2010 and 2015. Six of the patients with de novo CD and five of those with persistent/relapsed disease had a suspected abnormality on conventional MRI.

METHODS

All patients underwent (11)C-methionine PET-CT. For pituitary imaging, co-registration of PET-CT images with contemporaneous SPGR MRI (1 mm slice thickness) was performed, followed by detailed mapping of (11)C-methionine uptake across the sella in three planes (coronal, sagittal and axial). This allowed us to determine whether suspected adenomas seen on structural imaging exhibited focal tracer uptake on functional imaging.

RESULTS

In seven of ten patients with de novo CD, asymmetric (11)C-methionine uptake was observed within the sella, which co-localized with the suspected site of a corticotroph microadenoma visualised on SPGR MRI (and which was subsequently confirmed histologically following successful transsphenoidal surgery (TSS)). Focal (11)C-methionine uptake that correlated with a suspected abnormality on pituitary MRI was seen in five of eight patients with residual or recurrent Cushing's syndrome following first TSS (and pituitary radiotherapy in two cases). Two patients elected to undergo repeat TSS with histology confirming a corticotroph tumour in each case. In two patients with the ectopic ACTH syndrome, (11)C-methionine was concentrated in sites of distant metastases, with minimal uptake in the sellar region.

CONCLUSIONS

(11)C-methionine PET-CT can aid the detection of ACTH-secreting tumours in Cushing's syndrome and facilitate targeted therapy.

The value of 11C-5-hydroxy-tryptophan positron emission tomography in neuroendocrine tumor diagnosis and management: experience from one center

Many neuroendocrine tumors (NET) are small and may escape localization by conventional imaging techniques. In such cases, 11C-5-hydroxy-tryptophan (11C-5-HTP) positron emission tomography (PET) has been tested as an additional diagnostic tool. Nine patients with clinically, biochemically and/or histologically confirmed NET and negative computerized tomography (CT) or magnetic resonance imaging (MRI), and 111In-pentetreotide (Octreoscan) scintigraphy underwent imaging with 11C-5-HTP-PET/CT in order to: 1) detect the primary tumor lesion in three patients; 2) detect residual disease in two patients with appendiceal carcinoid, one with rectal carcinoid, one with midgut carcinoid, and one with ectopic ACTH secretion (EAS) due to residual pulmonary carcinoid; and 3) restage a patient with medullary thyroid carcinoma (MTC) and hepatic metastases. 11C-5-HTP-PET/CT detected lesions in the mediastinum in a patient with EAS due to a pulmonary carcinoid, further hepatic metastases in a patient with carcinoid syndrome (CS) from a NET of unknown primary, further hepatic metastases in the patient with MTC, and hepatic metastases in the patient with midgut carcinoid. The 11C-5-HTP-PET/CT findings contributed to radical cure of the patient with recurrent EAS, and pointed towards bilateral adrenalectomy in the patient with EAS without evident primary tumor. In addition, 11C-5- HTP-PET/CT directed towards combined surgical and medical treatment in the patient with CS and multiple rather than single hepatic metastases and in the patient with midgut carcinoid, and towards continuation of medical treatment in the patient with MTC. 11C-5-HTP-PET/CT is a useful imaging technique, providing additional information for the diagnosis, staging and decision-making regarding management of patients with NET.

Successful localization of ectopic ACTH-secreting bronchial carcinoid by selective pulmonary arterial sampling

Among patient with ACTH-dependent Cushing's syndrome, about 10-20% of those with ectopic ACTH syndromes (EAS) have occult or unknown tumors. Despite the intensive search for the culprit tumors by dynamic endocrine tests and imaging tests, it is often difficult to localize and confirm the source of occult ectopic ACTH secretion. We report a patient with EAS caused by a small bronchial carcinoid tumor, which was successfully localized by a selective pulmonary arterial sampling for the first time. A 69-year-old woman presented with typical Cushingoid features and elevated plasma ACTH and cortisol levels, which showed lack of circadian rhythm, no suppression by high-dose dexamethasone, and no response to CRH stimulation. No mass lesion was detected by pituitary MRI, and inferior petrosal sinus sampling showed no central to peripheral ACTH gradient. Although CT scan of the chest revealed a very small nodule in the right lung, it could not be confirmed by either somatostatin receptor scintigraphy or fluorodeoxyglucose positron emission tomography. Selective pulmonary arterial sampling of the wedged blood from a pulmonary artery branch affecting the nodule showed a marked ACTH gradient, and the lobectomy of the right middle lung resulted in dramatic decreases in plasma ACTH and cortisol levels. The resected tumor was diagnosed as a bronchial carcinoid tumor with positive immunostaining for ACTH. Thus, selective pulmonary arterial sampling, because of its more site-selective measurement of hormonal secretion, could be one of the useful tools to localize and confirm the ectopic ACTH production by a small pulmonary tumor.

The role of integrated (18)F-FDG PET/CT in identification of ectopic ACTH secretion tumors

The role of (18)F-Flurodeoxyglucose positron emission tomography ((18)F-FDG PET) scan in localization of ectopic Cushing's syndrome (EAS) tumor is still controversial. Here, we report on the use of integrated (18)F-FDG PET and computed tomography ((18)F-FDG PET/CT) in localization of EAS tumors in patients with ectopic Cushing's syndrome. Five patients, three men and two women, were reported, whose endocrine investigations and negative pituitary imaging were suggestive of ectopic ACTH secretion. (18)F-FDG PET/CT was performed to identify the source of ACTH secretion. Then the patients were suggested to perform pathologic examination. It turned out that all of these five patients have abnormal markedly intense FDG uptake lesions on (18)F-FDG PET/CT images. Four of them underwent lesion resection, whose plasma ACTH and serum cortisol levels returned to normal after the surgery. Also, they were at last remission from all the symptoms. Pathologic results showed one thymic carcinoid, one pulmonary carcinoid, one thymoma, and one pulmonary carcinoid with upper mediastinum carcinoid. Unfortunately, one patient died due to severe infection and electrolyte disorders. (18)F-FDG PET/CT technology integrates PET and CT imaging in one device so as to increase the accuracy of tumor localization and further improve the prognosis of the patients by curative resection.

Ectopic Cushing's syndrome: experience from a tertiary care centre

BACKGROUND & OBJECTIVE

Ectopic secretion of adrenocorticotropic hormone (ACTH) is rare, contributing to 10 per cent cases of endogenous Cushing's syndrome. We describe our experience of about two decades of patients with ectopic Cushing's syndrome (ECS) seen at a tertiary care centre from north India.

METHODS

Records of patients with ECS from 1985 to 2006 were retrospectively reviewed that included the presenting manifestations, clinical symptoms and signs, biochemical investigations including plasma cortisol, ACTH and high dose dexamethasone suppression test (HDDST), imaging modalities to localize the non pituitary source of ACTH production, management and follow up of these patients.

RESULTS

The study group included 12 patients (7 men) with mean (+/-SD) age at presentation 27.6 +/- 9.5 yr (range 13 to 48 yr) and the mean lag period between onset of symptoms and the diagnosis was 18.3 +/- 12.9 months with a range of 3 to 48 months. The weight loss (41.7%) followed by hyperpigmentation (25%) and infections (16.7%) were the common presenting manifestations. Cuticular atrophy (100%), hypertension (100%), bruise (92%) and proximal myopathy (83%) were the commonest signs. Plasma cortisol at 0800 h was 1267.3 +/- 483.3 nmol/l and at 2200 h was 1214.9 +/- 442.6 nmol/l indicating loss of circadian rhythm. The mean plasma ACTH was 221.1 +/- 55.9 (range 21.7 to 950 pg/ml). All but 2 patients had non-suppressibility of 0800 h plasma cortisol with HDDST. Five patients had thymic carcinoid, 3 had bronchial and one each had islet, hepatic and gut carcinoid and one had medullary thyroid carcinoma as a cause of ectopic ACTH secretion. The mean duration of follow up of these patients was 42.6 months and only two could sustain cure while remaining had either residual or recurrence.

INTERPRETATION & CONCLUSION

Ectopic Cushing's syndrome is a rare disease with varied manifestations and associated with increased morbidity and mortality. It presents with clinical features quite similar to classical Cushing's. Surgery with removal of primary tumour was found to be treatment of choice.

Two cases of ectopic adrenocorticotropic hormone syndrome with olfactory neuroblastoma and literature review

Olfactory neuroblastomas are rare, slow-growing malignant tumors, usually diagnosed at advanced stages. Ectopic adrenocorticotropic hormone (ACTH) syndrome caused by an olfactory neuroblastoma is extremely rare. We reported two Korean women who suffered from ectopic ACTH syndrome (EAS) caused by olfactory neuroblastomas. The first patient was a 66-year-old woman who had been diagnosed as olfactory neuroblastoma and refused the management two years before and the second patient was a 37-year-old woman on chemotherapy for olfactory neuroblastoma. In the first case, she presented the Cushingoid appearance with systemic edema and her tumor was removed surgically. ACTH secretion by the tissue was confirmed by immunohistochemistry. By contrast, the second patient presented as severe pneumonia caused by cytomegalovirus and was treated with anti-viral agent followed by chemotherapy and radiotherapy, and her residual mass remained. However, after treatment, both patients' plasma ACTH and cortisol levels returned to normal without any adrenolytic therapy. Considering the causative tumors of EAS can be rarely cured and EAS increases the susceptibility to infections, it is prudent to suppress any hypercortisolemia initially, apart from treating the causal malignancy.

Imaging of neuroendocrine tumors

Neuroendocrine tumors (NETs) are rare neoplasms, which are characterized by the presence of neuroamine uptake mechanisms and/or peptide receptors at the cell membrane and these features constitute the basis of the clinical use of specific radiolabeled ligands, both for imaging and therapy. Radiolabeled metaiodobenzylguanidine (MIBG) was the first radiopharmaceutical used to specifically depict and localize catecholamine-secreting tumors (pheochromocytomas, paragangliomas, and neuroblastomas) and is still regarded as a first-choice imaging technique for diagnosis and follow-up; in patients with malignant disease, MIBG scintigraphy is an essential step to select patients for (131)I-MIBG therapy. Scintigraphy with (111)In- or (99m)Tc-labeled somatostatin analogs has become the main imaging technique for NETs, particularly those expressing a high density of somatostatin receptors, such as gastroenteropancreatic tumors; this procedure is used routinely for localizing the primary tumor, evaluating disease extension, monitoring the effect of treatment and for selecting patients for radioreceptor therapy. Since the recent development of hybrid machines, it has been possible to obtain images that simultaneously hold both anatomic (computed tomography [CT]) and functional (single-photon emission computed tomography [SPECT] or positron emission tomography [PET]) information, with great impact on diagnostic accuracy. Significant improvements have been made during the past few years with the development of highly specific radiopharmaceuticals for PET studies that reflect the different metabolic pathways of NETs, such as glucose metabolism ((18)F-fluorodeoxyglucose), the uptake of hormone precursors ((11)C-5-hydroxytryptophan, (11)C- or (18)F-dihydroxyphenylalanine, (18)F-fluorodopamine), the expression of receptors ((68)Ga-labeled somatostatin analogs), as well as the synthesis, storage, and release of hormones ((11)C-hydroxyephedrine and others). Among these radiopharmaceuticals, (68)Ga-labeled somatostatin analogs are increasingly used in specialized centers in Europe for PET and PET/CT imaging and show very promising results with high diagnostic sensitivity. New somatostatin analogs with different receptor affinity as well as other peptides are currently under investigation and will further improve our diagnostic and therapeutic capabilities in the future.

A case of bronchopulmonary carcinoid tumor: the role of octreotide scanning in localization of an ectopic source of ACTH

BACKGROUND

Bronchopulmonary carcinoids are neuroendocrine tumors. They can present with Cushing's syndrome secondary to ectopic adrenocorticotropic hormone (ACTH) secretion. Curative resection is possible only after adequate localization of the ectopic source.

OBJECTIVE

To describe a case that illustrates the role of octreotide scanning in the management of a bronchopulmonary carcinoid.

RESULTS

The use of preoperative and postoperative octreotide scanning aided in performing a limited resection, thereby preserving the lung parenchyma.

CONCLUSIONS

We propose that octreotide scanning can be a very important and informative test in the management of carcinoid tumors. In situations when conventional imaging is not conclusive, octreotide scanning may be of help in determining the source of ectopic ACTH syndrome.

18Flurodeoxyglucose positron emission tomography in the localization of ectopic ACTH-secreting neuroendocrine tumours

OBJECTIVE

Neuroendocrine tumours (NET) are a rare cause of Cushing's syndrome. These tumours can be very small and therefore difficult to identify. Current localization techniques include CT, MRI and radioisotope scanning, but in a proportion of cases the NET remains occult. Positron emission tomography (PET) scanning, is a relatively new imaging modality that is increasingly used to detect and monitor lesions with high metabolic activity. We report on the use of PET scanning in the evaluation of the ectopic ACTH syndrome.

PATIENTS

Three patients with ectopic ACTH-dependent Cushing's syndrome with varying difficulty in NET localization are included in the report.

MEASUREMENT

Positron emission tomography scanning using 18flurodeoxyglucose (FDG) identifies tissue with high metabolic activity. 18FDG-PET scanning was used in each of these patients and the imaging is presented along with biochemical data.

RESULTS

In each case the NET was easily identified using 18FDG-PET, aiding clinical decision making and therapeutic outcome. A cure was identified by clinical resolution of symptoms and undetectable ACTH levels postsurgery.

CONCLUSIONS

18FDG-PET assisted in localizing small metabolically active NETs, suggesting this imaging modality may have a useful role in identifying NET causing Cushing's syndrome as a result of ectopic ACTH production.

Six cases of ectopic ACTH syndrome caused by thymic carcinoid

The ectopic ACTH syndrome (EAS) caused by thymic carcinoid is rare and its diagnosis remains a challenge to the endocrinologist. Here are six cases of EAS with a typical Cushing habitus accompanied by hyperpigmentation and hypokalemia. For all six patients, the high dose (8 mg) dexamethasone suppression test (HDDST) showed lack of suppression, computed tomography (CT) scanning documented anterior mediastinal masses, and the mediastenal tumors removed were confirmed as ACTH secreting thymic carcinoids by positive ACTH and NSE staining. Our data indicate that HDDST chest radiologic imaging and other laboratory examinations will greatly assist in diagnosing the thymic carcinoid-induced EAS at an earlier stage, which will significantly improve the long-term survival of the patient.

Use of radioguided surgery with [111In]-pentetreotide in the management of an ACTH-secreting bronchial carcinoid causing ectopic Cushing's syndrome

Intraoperative [111In]-pentetreotide scintigraphy with a hand-held gamma detector probe has recently been proposed to increase the intraoperative detection rate of small neuroendocrine tumors and their metastases. We report a case of a 28-yr-old woman with ectopic Cushing's syndrome due to an ACTH-secreting bronchial carcinoid, in whom the use of radioguided surgery improved disease management. At presentation, radiolabeled pentetreotide scintigraphy was the only procedure able to detect the ectopic source of ACTH. After radiologic confirmation, the patient underwent removal of a bronchial carcinoid, with disease persistence. After surgery, pentetreotide scintigraphy showed pathologic uptake in the mediastinum not previously detected at surgery and only subsequently confirmed by radiologic studies. Despite a second thoracic exploration, hormonal, scintigraphic, and radiological evidence of residual disease persisted. Radioguided surgery was then performed using a hand-held gamma probe 48 h after iv administration of a tracer dose of radiolabeled [111In-DTPA-D-Phe1]-pentetreotide, which permitted detection and removal of multiple residual mediastinal lymph node metastases. Clinical and radiologic cure, with no evidence of tracer uptake at pentetreotide scintigraphy, was subsequently observed. The use of an intraoperative gamma counter appears a promising procedure in the management of metastatic ACTH-secreting bronchial carcinoids.

Successful use of 111In-pentetrotide scintigraphy for localizing ectopic adrenocorticotropin-producing bronchial carcinoid tumor in a patient with Cushing's syndrome

A 34-year-old man was diagnosed with clinical Cushing's syndrome based on circadian fluctuation of plasma adrenocorticotropin and serum cortisol levels and Liddle's-method. The presence of ectopic adrenocorticotropin production was suspected. Urine 5-hydroxyindoleaceturic acid level was high. Chest computed-tomography scan revealed a mass in the right upper lung. 111In-pentetrotide scintigraphy demonstrated marked accumulation in the right upper lung. We suspected an adrenocorticotropin-producing bronchial carcinoid. Plasma adrenocorticotropin and serum cortisol levels decreased immediately following resection of the tumor. Adrenocorticotropin production by tumor cells was confirmed by immunohistochemistry. This case indicates 111In-pentetrotide scintigraphy could be successfully used to identify and localize ectopic adrenocorticotropin-producing bronchial carcinoid.

Difficulties in diagnosis and treatment of ectopic ACTH-producing tumors of the chest

It is widely accepted that surgery is the first choice treatment for ACTH-secreting tumors, most of them being lung or bronchial tumors. However, the localization of such lesions is rather difficult and it needs a compelling work-up. Here we present the results of different hormonal and imaging investigations and the surgical outcome of three patients with ectopic Cushing's syndrome.

Thallium-201 scintigraphy was useful in diagnosing ectopic ACTH syndrome due to bronchial carcinoid

Abstract. Initial investigations of a 70-year-old woman with clinical Cushing's syndrome, including overnight dexamethasone suppression test, CRH test, and pituitary MRI, suggested the presence of ectopic ACTH production. Thoracic computed tomography (CT) scan revealed a mass measuring 7 mm in the right lung, but it was thought to be an incidental opacity, leaving the source of ectopic ACTH undetermined for several years. During this period, although the size of the lung opacity did not change remarkably, serum cortisol levels became elevated to 43 microg/dl, and the patient's symptoms worsened. Tl-201 SPECT demonstrated intense accumulation in the right lung. The mass was surgically resected using thoracoscopy to investigate it as the focus of ACTH production. Histological and immunohistochemical examination confirmed that the area of intense Tl-201 uptake was an ACTH-producing bronchial carcinoid. Plasma ACTH and cortisol levels decreased immediately after the surgery. In conclusion, this case demonstrated Tl-201 scintigraphy as a useful tool in identifying the location of an ACTH-producing bronchial carcinoid.

Cavernous sinus sampling is highly accurate in distinguishing Cushing's disease from the ectopic adrenocorticotropin syndrome and in predicting intrapituitary tumor location

Inferior petrosal sinus sampling (IPSS) is used to distinguish pituitary Cushing's disease from occult cases of the ectopic ACTH syndrome, but is limited in that it requires the use of ovine CRH (oCRH) and is not highly accurate at predicting the intrapituitary location of tumors. This study was designed to determine whether cavernous sinus sampling (CSS) is as safe and accurate as IPSS, whether CSS can eliminate the need for oCRH stimulation, and whether CSS can accurately predict the intrapituitary location of tumors. Ninety-three consecutive patients with ACTH-dependent Cushing's syndrome were prospectively studied with bilateral, simultaneous CSS before and after oCRH stimulation. Prediction of a pituitary or ectopic ACTH source was based on cavernous/peripheral plasma ACTH ratios. Intrapituitary tumor location was predicted based on lateralization (side to side) ACTH ratios. These predictions were compared to surgical outcome in the 70 patients who had surgically proven pituitary (n = 65) or ectopic (n = 5) disease. CSS distinguished pituitary Cushing's disease from the ectopic ACTH syndrome in 93% of patients with proven tumors before oCRH administration and in 100% of patients with proven tumors after oCRH. It was as safe and efficacious as published IPSS results. CSS accurately predicted the intrapituitary lateralization of the tumor in 83% of all patients and 89% of those patients with good catheter position and symmetric venous flow. CSS is as safe and accurate as IPSS for distinguishing patients with pituitary Cushing's disease from those with the ectopic ACTH syndrome. In addition, CSS appears to be superior to IPSS for predicting intrapituitary tumor lateralization.

Lack of utility of (111)In-pentetreotide scintigraphy in localizing ectopic ACTH producing tumors: follow-up of 18 patients

Octreotide scintigraphy has been advocated as the principal imaging modality for localizing ectopic ACTH-secreting tumors in Cushing's syndrome. To assess its usefulness we reviewed the course of 18 consecutive patients with ectopic ACTH-producing tumor. Imaging included (111)In-pentetreotide scintigraphy, computed tomography (CT), and/or magnetic resonance imaging (MRI). Tumor was detected initially in 7/18 patients, and in 3/18 during follow-up. No ACTH-secreting tumor was detected by octreotide scintigraphy when CT/ MRI were negative. Seventeen of forty octreotide scintigrams were abnormal. CT and/or MRI confirmed tumors in 10, but demonstrated nonendocrine lesions in association with 6 false positive octreotide scintigrams. Hepatic venous sampling for ACTH refuted one lesion detected by octreotide and CT scans. Twenty-three of forty octreotide scintigrams were normal. Of these, 8 were false negative, as CT and/or MRI detected tumor; 10 agreed with negative CT and MRI, and 5 correctly refuted false positive CT and/or MRI scans. Repeated CT/ MR, but not octreotide scintigraphy, led to tumor resection in 2 patients. We conclude that octreotide scintigraphy does not offer greater sensitivity than CT/MRI and that false positive scans are common. Although octreotide scintigraphy may be helpful in selected cases, it is not a significant advance over conventional imaging for ectopic ACTH-secreting tumors.

Usefulness of somatostatin receptor scintigraphy in patients with occult ectopic adrenocorticotropin syndrome

SRIF receptor scintigraphy (SRS) has been proposed for the localization of ectopic ACTH-secreting tumors responsible for Cushing's syndrome. However, in most cases reported, the tumors were also visible using conventional imaging. Therefore, the usefulness of SRS in localizing truly occult ectopic ACTH-secreting tumors remains unknown. We report the results of SRS in 12 patients with ectopic ACTH syndrome (EAS) and in whom the source of ACTH was occult at presentation despite carefully performed conventional imaging. The diagnosis of EAS was made by identification of an ACTH-secreting tumor during follow-up in 5 patients or given a pituitary-to-peripheral ACTH ratio of 1.9 or less during petrosal sinus sampling combined with CRH injection and a negative pituitary magnetic resonance imaging (MRI). Whole-body planar SRS, using (111)In-pentetreotide, was performed 19 times in the 12 patients during initial workup and/or follow-up. Axial tomography imaging (single-photon emission-computed tomography) was performed in 7 of these. Conventional imaging was performed within a month of SRS, allowing comparison of the two approaches for the localization of the ACTH-secreting tumors. In addition, the response of plasma cortisol, after a single injection of 200 microg octreotide, was studied in 6 patients. Five patients had negative SRS and conventional imaging studies. The source of ACTH secretion remains occult despite 10-55 months of follow-up in four of these, whereas a 2-cm ileal carcinoid tumor, with liver micrometastases, was found at laparotomy in one patient, 14 months after presentation. SRS was positive in 4 of 12 patients. It was false-positive in 1 patient with follicular thyroid adenoma. Nineteen months after presentation, SRS identified liver metastasis that was also visible using MRI in one patient, but the primary tumor remains occult. SRS identified a 10-mm pancreatic tumor that became detectable, using computed tomography (CT) scanning 9 months later, in 1 patient; and 2 mediastinal lymph nodes of 10 mm, previously ignored by MRI, in another patient, whereas no tumor was detectable within the parenchymal lung. SRS had little influence on therapeutic options in these 2 patients, in whom no final diagnosis could be made. Repetition of SRS during the follow-up of patients with previously negative scintiscans was useless. Conventional imaging was positive in 6 of 12 patients. In the 2 patients with pancreatic tumor and isolated mediastinal lymph nodes, conventional imaging studies were interpreted as positive only after the results of SRS. One patient had liver metastasis that was also visible using SRS. Thin-section CT scanning visualized ACTH-secreting bronchial tumors and metastatic mediastinal lymph nodes of 10-15 mm in diameter in 3 patients after 14-72 months of follow-up, whereas SRS was negative. There was no evident relationship between the endocrine status (hyper- or eucortisolism) and the results of SRS. The in vivo response of plasma cortisol to octreotide correlated to the results of SRS in 4 of 6 cases. In conclusion, both imaging procedures had a low diagnostic yield in this series. However, the sensitivity of SRS for the detection of bronchial carcinoids was lower than that of thin-section CT scanning. We therefore advocate the use of conventional imaging, including thin-section CT scanning of the chest, analyzed by experienced radiologists, as the first-line investigation in patients with occult EAS. SRS should not be repeated during the follow-up in patients with a previously negative scintigram.

Computed tomography appearance of the thymus and anterior mediastinum in active Cushing's syndrome

Computed tomography (CT) evaluation of the thymus and anterior mediastinum is an important aspect of the investigation of patients with ACTH-dependent Cushing's syndrome in order to exclude an ACTH-secreting carcinoid tumor. We have reviewed the CT imaging of the thymus and anterior mediastinum in a series of 85 patients (55 females; median age 41, range 7-77 yr) with active Cushing's syndrome as there are few data on the range of appearances in hypercortisolemic states. One patient had a thymic carcinoid tumor (24 x 18 mm). Of the others, 28/84 (33%) patients showed thymic remnant tissue, consisting of either nodule(s) at least 5 mm diameter (n = 21, mean diameters 12.5 +/- 5 x 9.6 +/- 4 mm), or triangular bilobed glands (n = 7, mean thickness of the body, right and left limbs 25 +/- 7, 14 +/- 3, and 12 +/- 5 mm). Thymic involution appeared in 56/84 (67%) patients, ranging from small nodule(s) of less than 5mm diameter to linear soft tissue strands and complete fatty replacement. Patients with thymic remnant tissue were younger than those with thymic involution (P < 0.05). The thymic carcinoid tumor could be distinguished from remnant tissue on the basis of age and size. The presence of anterior mediastinal nodule(s) in hypercortisolemia need not imply the presence of a thymic carcinoid tumor, although in older patients this should arouse suspicion.

Endosonography of the adrenal glands: normal size--pathological findings

Transabdominal sonography of the adrenal glands frequently is non-successful. It was the aim of this project to improve the imaging of the adrenal glands using high resolution sonography in order to obtain information about even small changes in these organs. Therefore, endosonographic imaging was investigated using an endosonoscope PENTAX FG32UA. The correct identification of the adrenal glands was examined in five human cadavers. A total of 58 patients with 113 adrenal glands (in 3 cases history of unilateral adrenalectomy) were investigated. 109 adrenal glands (97%) were identified and evaluated. Healthy adrenal glands are slightly hyperechoich and regarding their echogeneity comparable to other endocrine organs such as the testes or the thyroid. Adrenal size can be determined as largest cross sectional area and was found to be 216 +/- 93 mm2 right and 231 +/- 98 mm2 left. In the adrenal glands which could be imaged by endosonography, all findings detected by CT (n = 33) or MRI (n = 19) could also be demonstrated endosonographically. Additional information as compared to CT/MRI was obtained in 7 out of 33 and in 6 out of 19 patients. This concerns in particular differentiation between tumor and hyperplasia and detection of small adrenal adenomas. High resolution endosonography of the adrenal glands can provide information about adrenal gland morphology which cannot be obtained by any other diagnostic approach.

Ectopic Cushing's syndrome and pulmonary carcinoid tumour identified by [111In-DTPA-D-Phe1]octreotide

The differential diagnosis and management of Cushing's syndrome remain difficult, particularly for ectopic adrenocorticotropin (ACTH) syndromes resulting from small bronchial carcinoids. We report the case of a 41-year-old man with ectopic ACTH-dependent Cushing's syndrome. Two computed tomography scans of the thorax were normal and magnetic resonance imaging of the chest showed a 6-mm hyperintense T1-weighted area close to the left pulmonary hilus, interpreted as probably vascular by the radiologists. An [111In-DTPA-D-Phe1]octreotide scintigraphy scan demonstrated a positive image for somatostatin receptors in exactly the same location and surgery confirmed the presence of a small ACTH-secreting carcinoid tumour in the upper left lung lobe which was resected. Surgery cured the hypercorticism of the patient. The differential diagnosis of Cushing's syndrome and the procedure for localisation of an ACTH source are discussed.

Characterizing an ectopic secreting carcinoid with indium-111-DTPA-D-Phe-pentetreotide

This report describes a technique that increases the specificity of 111In-pentetreotide as evaluated in a patient with ectopic Cushing syndrome.

METHODS

Two separate SPECT studies were performed with different pharmacologic protocols, both including treatment with cold octreotide. The imaging protocol provides acquisitions at 4 and 24 hr after injection. The quantitative approach was based on the ROI activity (manually designed) of an area of pathological lung uptake (ROI-T) versus background (ROI-NT). Histological, histochemical and specific mRNA measurements confirmed the presence of an SSR2 receptor carcinoid in the lung.

RESULTS

The time course of ROI-T/ROI-NT is a linear increase between 4 and 24 hr. Washout with cold octreotide diminished the ROI-T activity content and the saturation protocol increased ROI-T/ROI-NT, confirming the specific nature of the uptake.

CONCLUSION

Displacement and saturation protocols in 111In-pentetreotide imaging demonstrated the specificity of tumor binding.

[Cushing syndrome disclosing bronchial neuroendocrine carcinoma: value of scintigraphy with octreotide]

A 44-year-old man presenting with atypical maniac behavior and hypokaliemia was diagnosed with Cushing's syndrome and treated in emergency by bilateral adrenalectomy. Endocrine investigations were suggestive of an ectopic adrenocorticotropic (ACTH) secretion, both at baseline (mean ACTH levels = 215 pg/mL, beta-lipotropic hormone = 2329 pg/mL; molar ratio > 5) and after pharmacodynamic testing (lack of inhibition of ACTH by dexamethasone, blunted ACTH response to corticotropin releasing hormone). Ectopic ACTH secretion was investigated while pituitary ACTH secretion was suppressed by dexamethasone. A paradoxical rise of ACTH from 384 to 717 pg/mL was observed after subcutaneous administration of 500 micrograms octreotide. A right lung tumor that remained occult for 7 years was only revealed by octreotide scintigraphy, despite annual chest tomodensitometric examinations. Right inferior lung lobectomy allowed allowed for removal of a 13 mm tumor corresponding to a bronchial neuroendocrine carcinoma with positive immunostaining for ACTH. Mediastinal lymph nodes were histologically normal. Perioperative ACTH measurements, showing a more than 50% decrease from baseline at 15 minutes after tumor resection, were suggestive of complete tumor removal. This was confirmed 10 days postoperatively by undetectable ACTH levels and by a negative octreotide scintigraphy after surgery. This case report of an occult ACTH secreting bronchial neuroendocrine carcinoma illustrates the diagnostic value of octreotide scintigraphy, and the prognostic value of perioperative ACTH measurements in such cases.

Somatostatin analogs in ectopic corticotropin production

Eutopic corticotroph pituitary adenomas and adrenal cortisol-producing adenomas do not usually express somatostatin receptors. However, ectopic corticotropin (ACTH)-producing tumors often express somatostatin receptors. Thus, the octreoscan can detect and localize tumors in 80% of patients with ectopic ACTH syndrome, and so it can be used to differentiate between eutopic and ectopic ACTH-dependent bilateral adrenal hyperplasia. Octreotide therapy can produce a rapid and sustained reduction of ACTH and cortisol levels in patients with ectopic ACTH-dependent Cushing's syndrome and, in some, may be the only long-term therapy possible. Although no large series have been reported, a review of the literature reveals a large number of case reports that have demonstrated the effectiveness of octreotide.

Use of somatostatin analog for localization and treatment of ACTH secreting bronchial carcinoid tumor

A 29-year-old woman presenting with an ectopic adrenocorticotropic hormone syndrome and a nodule of the upper lobe of the left lung was explored by indium 111 (111In) octreotide scintigraphy. This showed a pathologic uptake by the nodule. Treatment with octreotide resulted in the rapid control of hypercortisolism prior to surgery.

Whole body and tomographic scan with 111In-pentetreotide: preliminary data

Since December 1993, in the 1st Nuclear Medicine Service of the University of Padua, eleven somatostatin-receptor scintigraphic studies with 111In-labelled pentetreotide have been performed. The patients (6 men and 5 women, age 28-68, mean 45 years) were affected by a variety of tumors which supposedly express somatostatin receptors: 2 meningotheliomatous meningiomas post-surgery; 2 glucagonomas with liver metastases observed on CT; 2 patients with suspicion of insulinoma; 2 carcinoids, one after surgery; 1 ectopic-ACTH Cushing's syndrome; 1 intracranial germinoma, post-surgery, in whom the study was requested to evaluate a doubtful finding of pulmonary metastatic lesion on CT; and 1 acromegaly showing, on MRI, and empty sella turcica occupied by and extraflexion of the lower portion of the chiasmatic cisterna without signs of adenoma and the sphenoidal sinus occupied by tissue wit inflammmatory characteristics. Somatostatin-receptor whole body scintigraphy was performed 4 and 24 hours after intravenous injection of 110 MBq 111In-pentetreotide (Octreoscan 111); spot images were acquired when judged necessary. In one case of glucagonoma, a tomographic scan (SPECT) was also performed to better evaluate the spatial relationship between the primitive pancreatic tumor and surrounding tissues. Focal accumulation of 111In-pentetreotide was scintigraphically detected in 5 of the 11 cases. Intense uptake of the radiopharmaceutical was observed in the meningiomas, in the glucagonomas with liver metastases, and in the case of acromegaly, corresponding to a GH-secreting adenoma. The negative scans seem to be true negative scans with the possible exception of one patient with a still unconfirmed suspicion of insulinoma, still not confirmed.

Successful localization of an occult ACTH-secreting bronchial carcinoid tumour with 111indium-DTPA labelled octreotide

Ectopic ACTH secretion due to occult carcinoid tumours is an occasional cause of ACTH dependent Cushing's syndrome. In many cases the ectopic source may be obvious, but sometimes no obvious source is evident, the so-called occult ectopic syndrome. Due to their small size, localization of such occult tumours, particularly bronchial carcinoids, may be extremely difficult. Whole body CT and venous sampling studies have been used but are not always successful in determining the site of such lesions. We report a 40-year-old patient with the ectopic ACTH syndrome due to a 0.6-cm bronchial carcinoid tumour which was successfully localized by 111indium-DTPA labelled octreotide scintigraphy.

111In-octreotide scintigraphy in endocrine tumors. Preliminary data

A large number of endocrine tumors express somatostatin receptors, and the use of radiolabeled somatostatin analogs has been recently introduced for their localization. Using in vivo scintigraphy with 111In-pentetreotide, primary tumor localizations were demonstrated in 3/3 carcinoids (2 intestinal carcinoids and 1 lung ACTH-secreting carcinoid; in 2 patients liver metastases larger than 1 cm were visualized), in 1/1 GH-secreting pituitary macroadenoma, and in 1/1 thyroid localization of MTC. Bone and/or lymph node metastases were imaged in 2/4 patients previously treated for MTC, with persistently high CT and CEA levels; in the other 2 patients the other scintigraphic techniques were also negative. Octreotide scintigraphy was negative in 2/2 insulinomas and in 2/2 ACT-producing pituitary adenomas. In 2 patients with carcinoid syndrome and 1 patient with Cushing syndrome due to ectopic ACTH, octreotide therapy induced a significant decrease in tumoral markers. Our preliminary data are in agreement with the results of larger series reported in literature: octreotide scintigraphy is a useful noninvasive tool to detect endocrine tumors expressing somatostatin receptors, particularly for carcinoids. It is of great use in the differential diagnosis of Cushing syndrome due to ectopic ACTH. Moreover, 111In-pentetreotide scintigraphy may be useful in selecting patients who may benefit from octreotide therapy to control hormonal hypersecretion effects.

Ectopic ACTH syndrome and CRH-mediated Cushing's syndrome

The ectopic ACTH syndrome accounts for a substantial number of patients with naturally occurring Cushing's syndrome. Despite the progress achieved in elucidating the pathophysiology of Cushing's syndrome, clinicians continue to experience diagnostic and therapeutic challenges. This is especially true in those patients presenting with disease mediated by ectopically produced ACTH and CRH. Patients with these disorders may be indistinguishable based on clinical grounds or simple biochemical and radiologic testing from those with Cushing's disease. However, this differentiation is critical because their therapies differ. While clinical researchers continue to develop more effective diagnostic techniques and therapies, further advances in the molecular and cell biology of ACTH and CRH-producing tumors will undoubtedly shed light on the pathogenesis of this perplexing, fascinating and still controversial entity.

Technetium-99m methoxyisobutylisonitrile localizes an ectopic ACTH-producing tumour: case report and review of the literature

Extensive investigation including whole-body examinations with computed tomography and magnetic resonance imaging did not detect the suspected ectopic ACTH-producing tumour in a patient with advanced Cushing's syndrome and hypokalemic alkalosis. Gamma camera examination with technetium-99m methoxyisobutylisonitrile (MIBI) depicted the tumour, which was localized in the anterior neck and mediastinum. This was later verified by surgery. 99mTc-MIBI is normally used for myocardial scintigraphy. Its accumulation is unspecific and merely reflects metabolic activity. Despite this, the present case shows that examination with this agent can provide important information with regard to tumour localization in a given situation, thereby serving as a complement to other imaging modalities. The current literature on 99mTc-MIBI for tumour diagnosis is reviewed.

Somatostatin analogs for the localization and preoperative treatment of an adrenocorticotropin-secreting bronchial carcinoid tumor

The diagnosis of the ectopic ACTH syndrome often remains difficult. Although bilateral inferior petrosal sinus sampling has recently offered a new approach, it does not help to localize an occult nonpituitary tumor. We report the case of a 45-yr-old woman whose hypercortisolism highly suggested the ectopic ACTH syndrome: elevated urinary free cortisol (3234 nmol/day, normal 28-143) was not suppressed by the high-dose dexamethasone test (2789 nmol/day); increased plasma ACTH (21.8 pmol/L, normal 2-11.4) did not respond to the ovine CRH test (23.8 pmol/L); and pituitary magnetic resonance imaging was negative. The thorax computed tomographic scan showed a questionable 7-mm nodular lesion in the upper part of the left lung. Because a 3-day trial of octreotide administration (200 micrograms sc every 8 h) induced a dramatic clinical and biological response with a drop in urinary free cortisol from 1738 to 441 nmol/day we performed a scintigraphy with [111In]pentetreotide; it revealed a single-well limited area of abnormal uptake at the exact location of the suspected thoracic lesion. This nodule was removed surgically after preparation of the patient by a 1-month treatment with octreotide: the tumor proved to be a typical bronchial carcinoid, containing extremely high concentrations of immunoreactive ACTH (198 pmol/mg wet wt tissue) and POMC messenger RNA by Northern blot. The presence of somatostatin receptors in the tumor was confirmed by in vitro radioautography. After surgery plasma cortisol and ACTH were undetectable. Somatostatin radioanalog scintigraphy should be considered as a new investigative tool in patients with suspected ectopic ACTH syndrome.

The radiological investigation of occult ectopic ACTH-dependent Cushing's syndrome

The radiological features of 14 patients with Cushing's syndrome due to 'occult' ectopic ACTH syndrome have been reviewed. In 11 of the 14 patients (79%), the ACTH-producing tumour was located in the thorax. Bronchial carcinoid tumours (eight patients) were the single most common source of 'occult' ectopic ACTH production with thymic carcinoid tumours (two patients) and mediastinal metastases from a medullary carcinoma of the thyroid gland (one patient) accounting for the other intrathoracic tumours. The tumours were usually small with five of the eight bronchial carcinoid tumours measuring between 4 and 10 mm in diameter. Since it remains difficult to distinguish between pituitary-dependent Cushing's disease and 'occult' ectopic ACTH-dependent Cushing's syndrome both clinically and biochemically, the role of radiology remains vital.

Ectopic adrenocorticotropic hormone syndrome: localization studies in 28 patients

A variety of imaging procedures were performed in 28 patients with ectopic adrenocorticotropic hormone (ACTH) syndrome in an attempt to localize the ACTH-producing tumor. Diagnosis was made on the basis of removal of an ACTH-producing tumor or biopsy of metastases in the 19 patients with a proved source and the absence of ACTH gradients in bilateral samples of the inferior petrosal sinuses in the nine patients in whom an ACTH-secreting tumor had not been localized. Eleven bronchial carcinoids, two thymic carcinoids, three pheochromocytomas, and three islet-cell tumors constituted the proved sources. The condition has been cured in eight patients, six are alive with residual tumor, and five have died. Of the nine patients with undetected sites of ACTH production, one has died of pneumocystis pneumonia and eight are being treated medically or with bilateral adrenalectomy. Computed tomography (CT) of the chest and abdomen was the most helpful study in the detection of these tumors. Selective arteriography (bronchial and visceral), systemic and portal venous sampling, and iodine-131 meta-iodobenzylguanidine scintigraphy failed to demonstrate tumors when findings at CT were negative. Bronchial carcinoids constituted most of the ACTH-secreting tumors in this study (58%) and in a review of four large series (47%). To assure early detection of these potentially malignant tumors, pulmonary CT should be performed every 6 months, even after hypercortisolism has been medically or surgically controlled.

ACTH-producing apudoma metastatic to the liver

A young man presented with combative psychosis and elevated levels of plasma adrenocorticotropic hormone (ACTH). A solitary vascular pancreatic mass and diffuse vascular hepatic nodules were demonstrated on selective splenic and hepatic arteriograms. These classic angiographic findings are used to emphasize the role of angiography in initial radiographic evaluation and to summarize the angiographic appearance of functioning pancreatic adenomas. Even though this is an aggressive tumor, early diagnosis and intensive treatment may allow prolonged remission, if not cure.

Adrenal scintigraphy in the morphological and functional evaluation of Cushing's syndrome

In recent years, cholesterol adrenal scintigraphy has been employed in the morphofunctional study of adrenal hypercorticism. Particularly in Cushing's syndrome, this noninvasive procedure can give a determinant contribution to distinguish ACTH-dependent from ACTH-independent forms. In our Institute, adrenal scintigraphy was performed in 77 patients with Cushing's syndrome diagnosed on clinical grounds confirmed by laboratory investigations and functional tests (17 with cortisol-secreting adenoma, 54 with pituitary ACTH-dependent bilateral adrenal hyperplasia, 2 with ectopic ACTH-dependent bilateral hyperplasia and 4 with bilateral nodular hyperplasia). Three distinct scintigraphic patterns have been identified. The 56 patients with ACTH-dependent Cushing's syndrome showed bilateral symmetric or slightly asymmetric visualization of the adrenal glands; in the 17 patients with ACTH-independent Cushing's syndrome the adrenal scintigraphy only visualized the gland harboring the adenoma; finally, a marked asymmetric visualization of the glands was observed in the 4 patients with adrenal nodular hyperplasia. These data confirm that adrenal scintigraphy is able to distinguish between ACTH-dependent and ACTH-independent Cushing's syndrome and reliably lateralizes adenomas when they are present. Moreover, the morphofunctional information obtained by this procedure, together with the high resolution morphological data by computerized tomography, allows to recognize the presence of bilateral nodular hyperplasia, an uncommon cause of Cushing's syndrome.