Learning Objective

Apply standard tumor nomenclature to classify neoplasms by tissue of origin and distinguish benign from malignant tumors.

General Principles

• Carcinoma refers to a malignant tumor of epithelial origin.
• Sarcoma refers to a malignant tumor of mesenchymal origin.
  👉 Both terms generally imply malignancy.

Benign vs Malignant Tumors

Benign tumors are typically:

• Well differentiated
• Well circumscribed
• Low mitotic activity
• Noninvasive
• Do not metastasize
• Lack necrosis

Malignant tumors (cancers) often demonstrate:

• Poor differentiation (anaplasia)
• Rapid, erratic growth
• Local tissue invasion
• Metastatic potential
• Reduced apoptosis

Non-Neoplastic Masses

Hamartoma

• Disorganized overgrowth of mature tissue native to the organ
• Example: Peutz–Jeghers polyps

Choristoma

• Normal tissue located in an abnormal (ectopic) site
• Example: Gastric mucosa in the distal ileum (Meckel diverticulum)

Common Tumor Names by Cell Type