Heterogeneous

In a pathology report, the term heterogeneous refers to a tissue, cell population, or structure that is made up of different components, types, or appearances rather than being uniform or consistent. Pathologists use this term to describe findings that vary in size, shape, colour, or composition within the same specimen. The opposite of heterogenous is homogenous.

When do pathologists use the term “heterogeneous”?

Pathologists often use the term “heterogeneous” in the following contexts:

• Tissue composition: When a sample contains a mixture of different cell types or tissue structures. For example, a tumour might be described as heterogeneous if it contains areas with different types of cancer cells or varying patterns of growth.
• Staining characteristics: When the way cells or tissues take up stains (used to highlight structures under a microscope) varies across the specimen. This might indicate areas with different biological properties or levels of activity.
• Size and shape variability: When cells or structures within the sample vary in size or shape. This can be seen in conditions with abnormal cell growth or transformation.

Examples of use

1. Heterogeneous tumour: A pathologist might describe a tumour as heterogeneous if it contains areas of necrosis (dead cells), areas with different types of cancer cells (e.g., some regions with glandular patterns and others with solid growth), or if there are differences in the grade or aggressiveness within different parts of the tumour.
   • Example: “The tumour shows a heterogeneous appearance with both gland-forming adenocarcinoma and solid areas lacking glandular differentiation.”
2. Heterogeneous staining: In immunohistochemistry, a pathologist might note that staining is heterogeneous if some areas of the tissue sample show strong staining while others show weak or no staining, suggesting variability in the expression of the marker being tested.
   • Example: “The immunohistochemical staining for CD138 is heterogeneous, with some regions showing strong membranous staining and others showing weak to no staining.”
3. Heterogeneous cell population: A biopsy might be described as having a heterogeneous cell population if the cells vary significantly in size, shape, or nuclear features. This could indicate a reactive process or a malignancy with mixed features.
   • Example: “The lymphoid infiltrate is heterogeneous, composed of a mixture of small, mature lymphocytes and larger, atypical cells with irregular nuclei.”