Keratin 7 immunohistochemistry reveals patterns of cell populations in liver biopsies from patients with MASLD

Aims Metabolic-associated steatotic liver disease (MASLD), which encompasses metabolic associated steatotic liver (MASL) and metabolic-associated steatohepatitis (MASH), is the most common chronic liver disorder worldwide. Fibrosis stage remains the most dependable histological predictor of prognosis; however, routine stains do not fully capture regenerative and injury-related processes. Keratin 7 (K7) immunohistochemistry highlights bile ducts (BDs), ductular reaction (DR), hepatic progenitor cells (PCs) and intermediate hepatocytes (IHs), all of which are involved in regeneration and fibrogenesis. This study aims to quantify K7-positive cell populations across histological stages of MASLD to enhance disease characterisation and evaluate the diagnostic value of K7 immunohistochemistry in this setting. Methods Archived liver biopsies from a clinically well-characterised cohort of 36 patients (17 MASH, 19 MASL) were stained for K7, digitised and analysed using QuPath with manual expert review. K7-positive structures were classified into BD, DR, PC or IH, with over 10 000 objects quantified. Profile densities and portal tract normalised ratios were calculated and correlated with clinical, biochemical and histological grading and staging by the Steatosis Activity and Fibrosis score. Results PC showed the strongest association with necro-inflammatory activity, peaking at grade 3. DR density increased significantly with fibrosis, supporting its role as an early marker of disease progression. IH was notably higher in MASH than in MASL, resulting in higher IH/DR ratios. Conclusion Specific quantitation of K7-positive cell populations can refine the diagnosis of MASLD and complement routine scoring in clinical trials to improve patient stratification.