Ectopic ACTH secretion due to a bronchopulmonary carcinoid localized by somatostatin receptor scintigraphy

Treatment of endocrine pancreatic tumors

Endocrine pancreatic tumors are rare with an incidence of 4 per million inhabitants. Most tumors are malignant except for insulinomas that usually are benign. They are slowly growing in the majority of cases but there are exceptions with rapidly progressing malignant carcinomas. Because of the rarity of these tumors large randomized trials are difficult to accomplish. However, most physicians treating these patients agree that surgery should be considered in all cases and that medical treatment with chemotherapy and biotherapy is well established for this group of patients.

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.

Localization of ectopic corticotropin-producing carcinoid tumor with use of indium-111 pentetreotide scintigraphy

OBJECTIVE

To report on the diagnosis of ectopic corticotropin (adrenocorticotropic hormone [ACTH])-producing bronchial carcinoid tumor by indium-111 pentetreotide (octreotide scan) scintigraphy.

METHODS

We present a case of ectopic ACTH syndrome caused by an occult bronchial carcinoid tumor arising in a lymph node and review the pertinent literature.

RESULTS

Biochemical diagnosis of ACTH syndrome can be difficult, and conventional imaging modalities often do not demonstrate these small carcinoid tumors. After biochemical proof of the presence of ectopic ACTH syndrome in our patient, conventional radiographic studies did not demonstrate any lesions. An octreotide scan showed a lesion in the lung, which was confirmed surgically. ACTH values returned to normal after resection of the lesion, and octreotide scans confirmed the completeness of surgical resection. The carcinoid tumor originated in a lymph node outside the bronchus. The differential diagnosis of ACTH syndrome, the localization of ectopic ACTH-producing tumors, the bronchial carcinoids, and the uniqueness of the carcinoid tumor arising in a lymph node are briefly discussed.

CONCLUSION

Octreotide scintigraphy is useful in localizing occult carcinoid tumors and can be used in the follow-up of patients after successful removal of these tumors.

Ectopic pro-opiomelanocortin syndrome

Ectopic POMC syndrome remains one of the most challenging differential diagnoses in endocrinology. Recent progress in the understanding of the tissue specific regulation of POMC gene expression and new insights into the processing of the POMC peptide in nonpituitary tissues has helped elucidate some of the molecular events leading to ectopic expression and secretion of POMC peptides. Corticotropin and other POMC-derived peptides have diverse effects on adrenal steroidogenesis, growth, and extra-adrenal tissues. Differences in POMC gene regulation in the corticotrope versus ectopic POMC-producing tumors provides a scientific framework for the clinical distinction between eutopic and ectopic Cushing's syndrome. In an attempt to revisit recent basic and clinical advances in the diagnosis of ectopic POMC syndrome the authors undertook an extensive literature review of 530 cases in 197 published papers and provided a molecular biologic, demographic and diagnostic update. According to this review, the four most common causes of ectopic POMC syndrome are the small cell carcinoma of the lung (27%), bronchial carcinoids (21%), islet cell tumor of the pancreas (16%), and thymic carcinoids (10%). Although the clinical features of patients with ectopic POMC syndrome are similar to those with Cushing's disease, subgroup analysis reveals a broad spectrum of severity and progression of signs and symptoms of hypercortisolism. The endocrine workup of a patient with suspected ectopic POMC syndrome includes the establishment of pathologic hypercortisolism, diagnosis of corticotropin dependency, and the differential diagnosis of corticotropin-dependent Cushing's syndrome. The use of a variety of baseline endocrine values, dynamic endocrine testing, and invasive procedures leads to the correct diagnosis in the majority of patients with ectopic POMC syndrome. Diagnostic imaging, including conventional radiological techniques and somatostatin receptor scintigraphy, aids in the correct localization and eventual treatment of ectopic POMC production.

[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.