Patient with synchronous low grade leiomyosarcoma of the thigh, primary pancreatic neuroendocrine tumor, and lung metastases: Why biopsy of metastases should be the standard.

Abstract

A group of well-defined adult neuroendocrine tumors (NETs) have variable but most often indolent biologic behavior and characteristic well-differentiated histologic features (1). The majority arise in the gastrointestinal (GI) tract (although carcinoid tumors may also arise in the lung and ovary), and collectively, they are referred to as gastroenteropancreatic NETs. They include carcinoid tumors, pancreatic islet cell tumors (gastrinoma, insulinoma, glucagonoma, VIPoma, somatostatinoma), paragangliomas, pheochromocytomas, and medullary thyroid carcinomas. Neuroendocrine tumors comprise only 0.5% of all malignancies. The incidence is approximately 2/100,000. The main primary sites are the gastrointestinal tract (62-67%) and the lung (22-27%), and 12-22% present with metastatic disease. The 5-year survival is mainly associated with stage: 93% in local disease, 74% in regional disease and 19% in metastatic disease (2). Treatment of localized disease is surgical resection if possible. In metastatic or advanced disease, locoregional treatments, as well as radionuclide therapies, may be considered. Additionally, in selected cases resection of the primary and metastatic tumors may impact outcome favorably. Although it has no significant effect on tumor growth, biotherapy with somatostatin analogs and/or interferon-α is recommended for either well-differentiated or functioning tumors for symptomatic relief. On the other hand, chemotherapy may be effective in the treatment of those tumors characterized by a poor differentiation grade and a high proliferation rate (3). Soft tissue sarcomas include a large variety of malignant neoplasms that arise in the extraskeletal mesenchymal tissues of the body. Approximately 10,390 cases are diagnosed annually in the United States, representing only 0.72 percent of all new cancers (4). Roughly 80 percent of sarcomas originate from in soft tissue, the remainder from bone (4). The histopathologic spectrum of sarcomas is broad, presumably because the embryonic mesenchymal cells from which they arise have the capacity to mature into striated skeletal and smooth muscle, adipose and fibrous tissue, bone, and cartilage. Low grade sarcomas are capable of aggressive local growth but tend not to disseminate. Overall survival of patients with sarcoma has been shown to correlate with grade in multiple studies (5),(6). The sensitivity of PET scanning for primary sarcomas ranges from 74 to 100 percent (7),(8) and is greater for high and intermediate grade sarcomas (7) than it is for low grade sarcomas (7),(9). In one report, 50 percent of low-grade sarcomas did not take up more FDG than adjacent muscle (10).