Standard teaching is rare diseases are rearley suspected. This holds true in practice as well. Cancer of small intestine is not commonly suspected though we come across its occurance on and off. It may present as pain in abdomen or bleeding internally with altered colored that is black stools. It may present as ulcer or mass or stricture. Barium follow through will give the clue. Enteroscopy is not easily available nor a comprehensive procedure. Capsule endoscopy will give the clue. Stool for occult blood exam helps to raise suspicion Bar. Laparoscopy or formal laparotomy with resection of diseased part will be confirmatory.
Clinically it may be difficult to differentiate between tuberculosis , crohn's and cancer .
GIST- Gastrointestinal stromal tumour is been diagnosed quite frequently  these days. Wonderful pathology examination back up crux in diagnosis in such rare diseases.
Many effective chemotherapeutic agents  are available for better treatment
Dr. Shriniwas Deshpande MS
Consultant Surgeon
Samarth Gastroenterology
Pune, India
http://www.samarthgastroenterology.com
9960644561