The Journal of Clinical Endocrinology & Metabolism Vol. 92, No. 12 4512-4513
Copyright © 2007 by The Endocrine Society
A Pulmonary Adrenocorticotropin-Secreting Carcinoid Tumor Localized by 6-Fluoro-[18F]L-Dihydroxyphenylalanine Positron Emission/Computed Tomography Imaging in a Patient with Cushing’s Syndrome
S. Dubois,
O. Morel,
P. Rodien,
F. Illouz,
S. Girault,
A. Cahouet,
F. Lacoeuille,
M. Brousseau,
J. Picquet and
V. Rohmer
Départements d’Endocrinologie (S.D., P.R., F.I., V.R.), d’Anatomopathologie (M.B.), et de Chirurgie Thoracique (J.P.), et Unité de Radiopharmacie (A.C., F.L.), Centre Hospitalier Universitaire d’Angers, et Département de Médecine Nucléaire (O.M., S.G.), Centre Paul Papin, 49933 Angers, France; and Université d’Angers (P.R., J.P., V.R.), 49035 Angers, France
Address all correspondence and requests for reprints to: S. Dubois, Département d’Endocrinologie, Centre Hospitalier Universitaire, 4 rue Larrey, 49933 Angers cedex 09, France. E-mail: sedubois{at}chu-angers.fr.
A 17-yr-old male was evaluated for ACTH-dependent Cushing’s syndrome. Normal pituitary magnetic resonance imaging and the absence of a central-to-peripheral ACTH gradient on bilateral inferior petrosal sinus sampling suggested ectopic ACTH secretion. The patient had a 6-yr history of postinfectious bronchiectasis. The chest computed tomography (CT) scan showed widespread pulmonary lesions compatible with bronchiectasis. The [111In]pentetreotide scintigraphy (1) was normal. [18F]Fluorodeoxyglucose positron emission tomography (PET)/CT imaging (2, 3) revealed a mild uptake in the middle lobe of the right lung. Because the patient suffered from a respiratory infection, the specificity of the uptake was questioned.
6-Fluoro-[18F]L-dihydroxyphenylalanine ([18F]DOPA) PET/CT imaging (4, 5) was then performed. Two sets of images were obtained at 15 and 75 min after injection of [18F]DOPA. The 15-min images (early acquisition) showed, in the middle lobe of the right lung (Fig. 1
), an isolated focal accumulation of [18F]DOPA, which had almost disappeared on the 75-min images.
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FIG. 1. [18F]DOPA PET/CT imaging. The axial view (A) and the three-dimensional maximum intensity projection anterior image (D) show the right pulmonary [18F]DOPA focal uptake. The fusion image (C) was obtained by combining PET (A) and CT (B) acquisitions, showing a hot spot in the middle lobe of the right lung.
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The patient was cured with lobectomy. Histology revealed a multifocal typical bronchial carcinoid tumor with widespread, from 3–12 mm in diameter, well-marginated nodular tumors and one lymph node micrometastasis.
The efficacy of [18F]DOPA PET imaging in identifying carcinoid tumors depends on the ability of tumor cells to take up, decarboxylate, and store amino acids. In our case, the higher uptake intensity on early acquisition may be related to the poor efficiency of decarboxylating activity, after the cellular uptake, and rapid release of [18F]DOPA into the circulation. This suggests that early acquisition in [18F]DOPA PET/CT scans may detect carcinoid tumors that would otherwise be missed by the technique.
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Footnotes
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Disclosure Statement: The authors have nothing to declare
Abbreviations: CT, Computed tomography; [18F]DOPA, 6-fluoro-[18F]L-dihydroxyphenylalanine; PET, positron emission tomography.
Received June 15, 2007.
Accepted September 18, 2007.
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References
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