Metastatic well or moderately differentiated neuroendocrine tumors of the gastrointestinal tract and lung (NETs) are a fascinating and markedly heterogeneous group of generally indolent, but relentless cancers.
One hundred years after Oberndorfer coined the word “carcinoid,” neuroendocrine tumors (NETs) are thought to be rare tumors characterized by the capacity for hormone production and often an indolent course. Recent data from population-based registries have shown a significant rise in the diagnosed incidence of NETs over the past 3 decades.
The patient is a 39-year-old Caucasian male who presented with a right renal mass and painless gross hematuria. He underwent a right laparoscopic radical nephrectomy and the final pathology revealed a carcinoid tumor.
Primary neuroendocrine neoplasms of the lung represent a clinical spectrum of tumors ranging from the relatively benign and slow-growing typical carcinoid to the highly aggressive small-cell lung carcinoma. The rarity of carcinoids has made the role of radiation therapy in their management controversial. This review considers the results of published studies to generate treatment recommendations and identify areas for future research. Surgery remains the standard of care for medically operable disease. Histology plays the most important role in determining the role of adjuvant radiation. Resected typical carcinoids likely do not require adjuvant therapy irrespective of nodal status. Resected atypical carcinoids and large-cell neuroendocrine carcinomas have a significant risk of local failure, for which adjuvant radiation likely improves local control. Definitive radiation is warranted in unresectable disease. Palliative radiation for symptomatic lesions has demonstrated efficacy for all histologies. Collaborative group trials are warranted.
Malignant small bowel tumors are extremely rare, accounting for 0.1% to 0.3% of all malignancies. Fewer than 2,400 new cases of small bowel malignancy are reported in the United States each year. Malignant tumors, which account for about two-thirds of all primary small bowel tumors, consist of four primary subtypes: adenocarcinoma, carcinoid tumor, lymphoma, and sarcoma (or gastrointestinal [GI] stromal tumor). Each malignancy is characterized by unique predisposing factors, anatomy, and biology. The prevalence, pattern, and relevance of both regional lymph node and distant metastases differ. As a result, the study of malignant small bowel tumors, taken as an aggregate, is fraught with difficulty.
This slide show features various magnifications of pancreatic neuroendocrine tumors (PNETs) displaying granular cell-like, clear cell, and other features.