Types of Malignant Tumors: Carcinoma, Sarcoma, Lymphoma, Leukemia

Classification by Tissue of Origin

Malignant tumors (cancers) are categorized by the cell type from which they arise:

1. Carcinoma (~80–90% of cancers): Epithelial origin.
   • Skin (basal/squamous cell), lung (adenocarcinoma, squamous), breast, colon, prostate, pancreas, ovarian.
   • Subtypes: adenocarcinoma (glandular), squamous cell, transitional cell, undifferentiated.
2. Sarcoma (~1% of adult cancers): Mesenchymal (connective tissue) origin.
   • Bone (osteosarcoma), muscle (leiomyosarcoma, rhabdomyosarcoma), fat (liposarcoma), cartilage (chondrosarcoma), nerve sheath, vascular.
   • Also: GIST (GI stromal tumor), Kaposi sarcoma.
3. Lymphoma: Lymphoid tissue origin (lymph nodes, spleen, extranodal).
   • Hodgkin lymphoma (Reed-Sternberg cells).
   • Non-Hodgkin lymphoma (B-cell, T-cell, NK-cell; diffuse large B-cell, follicular, mantle cell, etc.).
4. Leukemia: Hematopoietic stem/progenitor cells in bone marrow → circulating malignant cells.
   • Acute (lymphoblastic ALL, myeloid AML) vs. chronic (CLL, CML).
   • Myeloid vs. lymphoid lineage.

Other Categories

• Germ cell tumors: Testicular, ovarian, mediastinal (seminoma, teratoma).
• Neuroendocrine tumors: Carcinoid, pancreatic NET, Merkel cell.
• Melanoma: Melanocytes (neural crest).
• Mesothelioma: Mesothelial lining (pleura, peritoneum).

Why Classification Matters

Determines staging system, treatment paradigm (surgery vs. systemic vs. radiation), molecular testing, and prognosis.