Macrophages in human tumours: an immunohistochemical study

Area of Science:

• Oncology
• Immunohistochemistry
• Histopathology

Background:

• Macrophages play a role in tumor microenvironments.
• Accurate identification of macrophage populations is crucial for understanding tumor behavior and developing targeted therapies.
• Histochemical and immunohistochemical methods are used to characterize cellular components within tumors.

Purpose of the Study:

• To evaluate the utility of non-specific esterase (NSE), acid phosphatase (AP), and lysozyme staining in identifying macrophages within human tumors.
• To compare the specificity and sensitivity of these staining methods in various tumor types.
• To assess the presence and distribution of lysozyme-positive macrophages (LPM) in malignant and benign lesions.

Main Methods:

• Histochemical staining for non-specific esterase (NSE) and acid phosphatase (AP).
• Immunohistochemical staining for lysozyme.
• Analysis of 45 human malignant tumors and 3 benign lesions.

Main Results:

• Lysozyme staining detected specific macrophages (LPM), with higher numbers observed in colonic tumors and intralesional LPM in gastric and duodenal tumors.
• Squamous and mesenchymal tumors showed no significant LPM.
• AP and NSE stained both macrophages and tumor cells, reducing their specificity in certain tumor invasion contexts. Neutrophils were also stained but distinguishable by nuclear morphology.

Conclusions:

• Lysozyme is a specific marker for a subset of macrophages in tumors, offering valuable insights into tumor-associated immune responses.
• Non-specific esterase and acid phosphatase are less specific due to cross-reactivity with tumor cells, limiting their use in stromal invasion scenarios.
• The distribution of LPM varies by tumor type, suggesting site-specific roles for these immune cells in human neoplasms.