Reticulin Stain

Reticulin stain selectively highlights reticular (type III collagen) fibers in tissue sections. It’s used to visualize the supporting framework and architecture of organs—especially bone marrow, liver, and spleen—to detect and grade fibrosis, evaluate marrow disorders such as myelofibrosis, and clarify tumor architecture or stromal changes. It helps pathologists assess altered tissue scaffolding in hematologic and hepatic diseases.

Reticulin abnormalities appear in bone marrow fibrosis (especially primary myelofibrosis and post‑polycythaemia/essential thrombocythaemia myelofibrosis), other myeloproliferative neoplasms and myelodysplastic syndromes, certain leukemias/lymphomas and metastatic carcinoma. Altered reticulin framework occurs in liver cirrhosis. Anti‑reticulin antibodies were historically linked to coeliac disease. It can also increase with granulomatous inflammation, chronic infection, radiation or toxic marrow injury.

The best stain for reticular fibers is a silver impregnation (reticulin) stain—classically Gomori’s reticulin or Gordon and Sweet methods. These silver stains selectively demonstrate type III collagen (reticular fibers) as black or brown‑black networks against a pale background, and are routinely used to evaluate tissue architecture in liver, bone marrow, lymph nodes, and tumor stroma.

Reticulin (reticular fibers, mainly type III collagen) creates a delicate meshwork in bone marrow that forms the scaffolding supporting hematopoietic cells and blood-forming niches. It maintains marrow architecture, helps anchor stromal and progenitor cells, and facilitates cell adhesion, migration and maturation. Increased reticulin indicates marrow scarring (fibrosis), which can disrupt normal blood cell production.

Reticulin fibers (type III collagen) are demonstrated by silver-based reticulin stains (e.g., Gomori’s). These argyrophilic fibers appear black or very dark brown against a pale or lightly counterstained background, highlighting the delicate supporting meshwork in tissues such as liver, bone marrow, and lymph nodes. Pathologists use this contrast to assess tissue architecture and fibrosis.

The special stain for tuberculosis is the Ziehl–Neelsen acid‑fast stain, which uses heat to drive carbol fuchsin into organisms and identifies acid‑fast bacilli like Mycobacterium tuberculosis by their resistance to acid‑alcohol decolorization. Alternatives include the cold Kinyoun acid‑fast stain and auramine‑rhodamine fluorescent stain, the latter offering greater sensitivity for sputum or tissue screening.