Reticulin

Reticulin is a term used to describe a delicate network of fibers composed mainly of type III collagen that forms a supportive scaffold in certain tissues. This reticular connective tissue forms a three‑dimensional meshwork that helps to organize and support parenchymal cells in organs such as the liver, spleen, lymph nodes, bone marrow, and some endocrine glands. Reticular fibers are produced by specialized fibroblastic cells, often referred to as reticular cells, and they contribute to the structural integrity and organization of the surrounding tissue.

The reticulin network is typically thin and less rigid than the collagen I–based framework found in many connective tissues. It interacts with other extracellular matrix components and basement membranes to create a flexible framework that accommodates tissue remodeling and cell movement.

Visualization and assessment in pathology rely on specialized staining. Reticulin fibers are highlighted with silver impregnation stains, such as Gomori’s reticulin stain or Gordon and Sweet’s method, which render the fibers dark against a lighter background. Immunohistochemical or molecular approaches can also be used to study type III collagen distribution in some contexts.

Clinical relevance lies in the use of reticulin staining to evaluate tissue architecture and fibrosis. In bone marrow, reticulin staining is used to assess marrow fibrosis and the integrity of the hematopoietic niche, with grading systems describing the extent of reticulin fiber proliferation or distortion. In the liver and other organs, changes in the reticulin network can reflect architectural disruption associated with fibrotic disease and aid in staging or differential diagnosis when used alongside other histological stains.

Overall, reticulin denotes a type III collagen–based fiber network that provides a supporting framework essential for tissue structure and function, particularly in hematopoietic and lymphoid tissues.