Diagnostic advances in APUDomas and other endocrine tumors: Imaging and localization

Abstract

The different diagnostic imaging modalities available for determining the location of the various APUDomas are discussed with reference to their advantages and disadvantages. The ability to image these lesions, and to be confident in their role in the underlying pathophysiology, and clinical neuroendocrine syndrome causing symptomatology and illness, has proved to be the key to successful treatment. In many instances it is not the diagnosis that is in question, but it is the extent of disease, the location of the lesion, or whether the anatomical abnormality under study is responsible for the complicating symptoms being considered, that are the crucial questions. The ability to locate APUDomas by a variety of direct and indirect imaging or regionalizing modalities, represent a magnificent advance in the management of these tumors. It should, however, be kept in mind that no one modality or diagnostic method can uniformly be relied upon. It is evident that a multimodal, interactive medical team approach is essential to the successful overall management of patients afflicted with these fascinating tumors.

Value of Somatostatin Receptor Scintigraphy for Preoperative Localization of Carcinoids

“…Although US, CT, and MRI are fairly accurate in showing liver metastases, they do not always allow us to judge the full extent of disease (i.e., the small and extraabdominal metastases) and therefore to answer the question about potential surgical cure. The localization of metastases by conventional imaging procedures is considerably better than for the primary lesion (CT 80%, US 70%, MRI 80%, and MiBG scan 60%) [5][6][7][8][9][10][11]. Still, 20% to 40% of metastases cannot be visualized by these techniques.…”

“…Because of the small size of most carcinoid primary lesions they are rarely detectable using conventional techniques such as CT, MRI, US, or barium meal (enteroclysis). The few data in the literature describe an accuracy for detecting primary tumors of 10% to 40% for CT, 10% to 40% for US, 20% for MRI, and 30% for barium meal [5][6][7][8][9][10][11][12].…”

“…In such cases, preoperative localization of the primary tumor tends to be difficult. It can be achieved by computed tomography (CT) or ultrasonogra-phy (US) in 10% to 40%, magnetic resonance imaging (MRI) in 20%, or 131 I-meta-iodobenzylguanidine scintigraphy (MIBG scan) in 60% of cases [5][6][7][8][9][10][11]. Frequently a barium meal or enteroclysis is helpful for localizing a midgut carcinoid [12].…”

“…Frequently a barium meal or enteroclysis is helpful for localizing a midgut carcinoid [12]. However, localization of metastases is routinely possible by US in 70%, CT in 80%, MRI in 80%, and MIBG scan in 60% of cases [5][6][7][8][9][10][11].…”