Tumors of small intestine may be classified, based on histology, into:
1. Epithelial tumors:
a. Adenoma
i. Tubular
ii. Villous
iii. Tubulovillous
b. Intraepithelial neoplasia (dysplasia) associated with chronic inflammatory diseases
i. Low-grade glandular intraepithelial neoplasia
ii. High-grade glandular intraepithelial neoplasia
c. Carcinoma:
i. Adenocarcinoma
ii. Mucinous carcinoma
iii. Signet-ring cell carcinoma
iv. Small cell carcinoma
v. Squamous cell carcinoma
vi. Adenonsquamous carcinoma
vii. Medullary carcinoma
viii. Undifferentiated carcinoma
![Carcinoid tumor of small intestine](http://howmed.net/wp-content/uploads/2013/08/Carcinoid-tumor-small-intestine-300x209.jpg)
d. Carcinoid tumor (Well differentiated endocrine neoplasm)
i. Gastrin cell tumour, functioning (gastrinoma) or nonfunctioning
ii. Somatostatin cell tumour
iii. EC (Enterochromafin) cell, serotonin-producing neoplasm
iv. L-cell, glucagon like peptide and PP (Pancreatic polypeptide)/PYY (Polypeptide YY)-producing tumour
e. Mixed carcinoid-adenocarcinoma
f. Gangliocytic paraganglioma
g. Others
2. Non-Epithelial tumors:
a. Lipoma
b. Leiomyoma
c. Gastrointestinal stromal tumour
d. Leiomyosarcoma
e. Angiosarcoma
f. Kaposi sarcoma
g. Others
3. Malignant Lymphomas:
a. Immunoproliferative small intestinal disease (includes alpha-heavy chain disease)
b. Western type B-cell lymphoma of MALT
c. Mantle cell lymphoma
d. Diffuse large B-cell lymphoma
e. Burkitt’s lymphoma
f. Burkitt like or atypical Burkitt’s lymphoma
g. T-cell lymphoma
- Enteropathy associated
- Unspecified
h. Others
4. Secondary Tumors
5. Polyps:
a. Hyperplastic (metaplastic)
b. Peutz-Jeghers
c. Juvenile