Small intestine cancer overview

# Overview
In oncology, small intestine cancer, also small bowel cancer and cancer of the small bowel, is a cancer of the small intestine. It is relatively rare compared to other gastrointestinal malignancies such as gastric cancer (stomach cancer) and colorectal cancer. Small intestine cancer can be subdivided into duodenal cancer (the first part of the small intestine) and cancer of the jejunum and ileum (the later two parts of the small intestine).  Several different subtypes of small intestine cancer exist.  These include:adenocarcinoma,gastrointestinal stromal tumor,lymphomaand carcinoid. Surgery is the most common treatment. Additional options include chemotherapy, radiation therapy or a combination.

# Historical Perspective
Small intestine cancer is a rare presentation and recent increase in its incident compelled the researchers to study it further. The information on historical perspective of small intestine cancer is limited.

# Classification
Small intestine cancer may be classified according to histology into adenocarcinoma, gastrointestinal stromal tumor, lymphoma, ileal carcinoid tumor, and sarcoma (most commonly leiomyosarcoma and rarely angiosarcoma or liposarcoma).

# Pathophysiology
Adenocarcinoma is the most common sub-type of small intestine cancer. Second most common is carcinoid tumor. Adenocarcinomas may be polypoid, infiltrating or they appear as annular constricting lesions in small intestine. On gross pathology, napkin ring appearance or polypoidal fungatining mass are characteristic findings of small intestine cancer. Carcinoid tumors of the smalls intestine are mostly associated with malignant tumors of the other sites. Gastrointestinal stromal tumors (GISTs) are the most common benign tumors of the gastrointestinal (GI) tract. Small intestinal lymphomas are of low-grade on histology and arise from mucosal-associated lymphoid tissues (MALT).

# Causes
There are no established causes for small intestine cancer. Cancer may arise in genetically predisposed individuals or they may arise sporadically. Environmental factors may play a role as well; however, there is no study demonstrating established risk factors.

# Differentiating from Other Diseases
Small intestine cancer must be differentiated from Crohn's disease, intestinal tuberculosis, ulcerative colitis, large intestine cancer, peptic ulcer disease, and irritable bowel syndrome (IBS).

# Epidemiology and Demographics
Males are more commonly affected with small intestine cancer than females. Male to female ratio is approximately 1.4 to 1. Small intestine cancer usually affects individuals of the African-Americans race. Caucasian individuals are less likely to develop small intestine cancer.

# Risk Factors
Common risk factors in the development of small intestine cancer are Crohn's disease, celiac disease, radiation exposure, hereditary cancer syndromes, smoking, and alcohol.

# Screening
There are no known screening protocols for small intestinal cancer detection.

# Natural History, Complications, and Prognosis
Clinical features and natural history of small intestinal tumors have not been clearly studied, as its a rare condition. Depending on the extent of the tumor at the time of diagnosis, the prognosis may vary.  However, the prognosis is generally regarded as poor. Small intestine adenocarcinoma is associated with a 5 year survival rate of 20%.

# Diagnostic Study of Choice
The diagnosis of a small intestine cancer is often made late as the symptoms are nonspecific (abdominal pain, weight loss, nausea and vomiting, occult GI tract bleeding). Early diagnosis requires a high index of suspicion. Histopathological analysis by tissue sample through biopsy of the lesion is the gold standard.

# History and Symptoms
Symptoms of small intestine cancer include abdominal pain, weight loss, nausea, bloating, loss of appetite, and jaundice.

# Physical Examination
Generally, the most common signs of small intestinal cancer are emaciation, lethargy, abdominal tenderness, abdominal mass, hepatomegaly, ascites, icterus, enlarged lymph nodes and pallor. Other signs include low-grade fever, discomfort on palpation, rectal bleeding, abdominal mass, and jaundice.

# Laboratory Findings
Some patients with small intestine cancer may have elevated concentration of liver enzymes, which is usually suggestive of possible spread to the liver or blockage of the bile duct.

# Electrocardiogram
There are no specific ECG findings related to cancer of small intestine.

# X-ray
X-ray images may be taken after barium swallow to see the lesions in small intestine. It may show filling defects, mucosal distortion and barium hold up if tumor of small intestine is present.

# CT scan
Abdominal CT scan may be diagnostic of small intestine cancer. Findings on CT scan suggestive of small intestine cancer include intrinsic mass with a short segment of bowel wall thickening.

# MRI
MRI and MR enteroscopy are other high definition imaging modalities that localize tumor, its boundaries, dimensions in small intestine. They are very helpful in staging the tumor.

# Echocardiography and Ultrasound
Echocardiography has no role in establishing the diagnoses of small intestine cancer. However, ultrasound may be very useful in early stages of the presentation which may help exclude other causes of abdominal symptoms from cancer of small intestine.

# Other Imaging Findings
Other diagnostic studies for localizing tumor of small intestine cancer include ultrasound, fluoroscopy and barium follow through x-rays.

# Other Diagnostic Studies
Other diagnostic studies for small intestine cancer include enteroscopy, capsule endoscopy and double balloon enteroscopy, which may directly visualize intestinal mucosa and take pictures through cameras. It may directly show tumor in the muscosa of intestinal wall and surrounding area.

# Medical Therapy
Best treatment for cure small intestine cancer is surgical resection with combination of chemotherapy or radiotherapy. If tumor is not curable palliative surgery may be done. Chemotherapy is used to reduce the likelihood of metastasis, shrink tumor size, and slow tumor growth. Chemotherapy is often applied after surgery (adjuvant), before surgery (neo-adjuvant), or as primary therapy if surgery is not indicated (palliative). Other therapies include radiation and support therapies.

# Surgery
Curative surgery is the primary modality for treating small intestine cancers, in combination with chemotherapy and radiotherapy.

# Primary Prevention
There are no established preventive measures to prohibit developing small intestinal cancers. However, limiting tobacco and alcohol use, moderate healthy diet consumption and treatment of gastroenteritis and other intestinal pathology with increased risk of carcinomatos changes in polyps, may decrease the incidence ofsmall intestinal cancers.

# Secondary Prevention
Once a patient is diagnosed with intestinal cancer preventing its recurrence is very important. Life style modification such as limiting tobacco and alcohol use, moderate healthy diet and treatment of gastroenteritis may decrease the recurrence of small intestinal cancers. Scheduled follow-up exams and tests to detect polyps and cancerous lesions in other parts of GIT are important and may detect it recurrence.