, ,

Rarely. The WHO’s classification of tumors of hematopoietic and lymphoid tissues doesn’t list any pure macrophage cancers (1). The closest to a cancerous macrophage cell type would be Histiocytoma.

OTOH, mouse cancer model studies suggest macrophages could support many types of solid tumors. Often, they’re the first hematopoietic cells at a tumor site. Unlike normal tissues, tumors are a unique microenvironment of proliferating and dying cells. Resulting low pH, oxygen tension and exposure to contents from constant dead cell turnover seems to drive such macrophages into a perpetual tissue repair and wound-healing mode. Ironically, in the case of many solid tumors, such efforts by the infiltrating macrophages instead seem to end up supporting tumor growth. Tumor-support functions attributed to such tumor-associated macrophages (TAMs) are many, key one being angiogenesis, necessary for the tumor’s growth and survival (see figures below from 2, 3).

Origin of TAMs is mostly based on mouse cancer model studies. Sequence of differentiation is along the lines of Bone marrow hematopoietic progenitor cells (HPCs) —> Promonocytes —> Monocytes —> Extravasate from blood circulation into tumor —> Differentiate into TAMs. Origin of human TAMs is still unknown. However, epidemiological studies suggest poor prognosis for macrophage infiltration in breast, cervix, gastric, Hodgkin’s lymphoma, prostate (4, 5, 6) but the opposite in colon cancer (4). Thus, TAMs may have different roles in different human tumors.

Role of macrophages in cancers could become better defined with therapy to specifically target them. However, such cancer therapy is in its infancy. Nevertheless effectiveness of at least one approved anti-cancer agent, Trabectedin, is conjectured to stem from its potent capacity to deplete TAMs (7).


1. Vardiman, James W. “The World Health Organization (WHO) classification of tumors of the hematopoietic and lymphoid tissues: an overview with emphasis on the myeloid neoplasms.” Chemico-biological interactions 184.1 (2010): 16-20.

2. Chapter 20, Tumor-Associated Macrophages. Antonio Sica , Laura Straus , and Paola Allavena. Pages 425 to 443. In Macrophages: Biology and Role in the Pathology of Diseases. Subhra K. Biswas & Alberto Mantovani, Editors. Springer.

3. Chapter 7, Vascular Modulatory Functions of Macrophages. Ioanna Keklikoglou and Michele De Palma. Pages 131 to 168. In Macrophages: Biology and Role in the Pathology of Diseases. Subhra K. Biswas & Alberto Mantovani, Editors. Springer.

4. Bingle, L., N. J. Brown, and C. E. Lewis. “The role of tumour‐associated macrophages in tumour progression: implications for new anticancer therapies.” The Journal of pathology 196.3 (2002): 254-265. https://www.researchgate.net/pro…

5. Steidl, Christian, et al. “Tumor-associated macrophages and survival in classic Hodgkin’s lymphoma.” New England Journal of Medicine 362.10 (2010): 875-885. http://www.nejm.org/doi/pdf/10.1…

6. Zhang, Qiong-wen, et al. “Prognostic significance of tumor-associated macrophages in solid tumor: a meta-analysis of the literature.” PloS one 7.12 (2012): Prognostic Significance of Tumor-Associated Macrophages in Solid Tumor: A Meta-Analysis of the Literature

7. Germano, Giovanni, et al. “Role of macrophage targeting in the antitumor activity of trabectedin.” Cancer cell 23.2 (2013): 249-262. https://www.researchgate.net/pro…