Epidemiology And Pathology

Although the precise incidence is unknown, it is estimated that one to three persons per million develop gastrinomas each year.2 Likewise, gastrinomas are the underlying cause in approximately 0.1 to 1% of patients with peptic ulcer disease.3 They occur in both sporadic and familial or inherited forms, with the former occurring in 80% of cases and the latter in 20%. The familial form is usually associated with multiple endocrine neoplasia (MEN) type I (Table 14-1). In this setting, most associated hor-monally functional neuroendocrine tumors of the pancreas or duodenum are gastrinomas. Gastrinomas are the most common malignant hormonally functional neuroendocrine tumor, and approximately 60% are found to have lymph node, regional, or liver metastases at initial surgical exploration.4 Histologically, these tumors are composed of monotonous sheets of small round cells with a uniform nucleus and cytoplasm and a general lack of mitotic figures. In general, they are well vascularized and tend to metastasize primarily to regional lymph nodes and the liver, although widespread metastases to the lung, bone, and brain can also occur. Grossly, tumors are usually encapsulated, firm, and pale or yellow-brown in color (Figure 14-1). They may be single or multiple and may range in size from < 1 cm to > 3 cm. When associated with MEN type I, studies suggest that gastrinomas are usually multiple and found most commonly within the duodenum.5 Approximately 80% of gastrinomas are found within the gastrinoma triangle (Figure 14-2), an area that includes the first and second portions of the duodenum and the head of the pancreas. Although rare, primary gastrinomas have also been found in the jejunum, stomach, liver, spleen, mesentery, ovary, and heart.6 In addition, cure of ZES has been reported after excision of solitary gastrinomas that

Table 14-1. CHARACTERISTICS OF MULTIPLE ENDOCRINE NEOPLASIA TYPE I

Mutation in MENIN gene (chromosome 11) Parathyroid hyperplasia Pituitary adenoma (rarely, hyperplasia) Multiple neuroendocrine tumors involving the pancreas and duodenum

Adrenocortical adenoma or carcinoma (rare) Thyroid adenoma

Carcinoid tumors of foregut or midgut (rare)

appear to have arisen within a lymph node. This has given rise to the idea of a lymph node primary gastrinoma.4 Gastrinomas of the duodenum and pancreas appear to have a similar incidence of overall metastases. However, pancreatic gastrinomas appear to have a higher incidence of liver metastases,

Figure 14-1. A, Gross specimen of a distal pancreatectomy showing the anterior view of a gastrinoma (outlined). In B, the same tumor has been elevated to show a posterior view (outlined). C shows a magnified view of the image shown in B. The dark structure on the right of the specimen in each case is the spleen.

Figure 14-2. The approximate boundaries of the gastrinoma triangle (shaded area).

Figure 14-1. A, Gross specimen of a distal pancreatectomy showing the anterior view of a gastrinoma (outlined). In B, the same tumor has been elevated to show a posterior view (outlined). C shows a magnified view of the image shown in B. The dark structure on the right of the specimen in each case is the spleen.

Figure 14-2. The approximate boundaries of the gastrinoma triangle (shaded area).

whereas duodenal tumors tend to have a higher incidence of metastases to lymph nodes.

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