Role of immunohistochemistry for interobserver agreement of Peritoneal Regression Grading Score in peritoneal metastasis.

Pressurized intraperitoneal aerosol chemotherapy (PIPAC)-directed therapy is a new treatment option for peritoneal metastasis (PM). The 4-tiered Peritoneal Regression Grading Score (PRGS) has been proposed for assessment of histological treatment response. We aimed to evaluate the effect of immunohistochemistry (IHC) on interobserver agreement of the PRGS. Hematoxylin and eosin (H&E)-stained and IHC-stained slides (n = 662) from 331 peritoneal quadrant biopsies (QBs) taken prior to 99 PIPAC procedures performed on 33 patients were digitalized and uploaded to a web library. Eight raters (five consultants and three residents) assessed the PRGS, and Krippendorff's alpha coefficients (α) were calculated. Results (IHC-PRGS) were compared with data published in 2019, using H&E-stained slides only (H&E-PRGS). Overall, agreement for IHC-PRGS was substantial to almost perfect. Agreement (all raters) regarding single QBs after treatment was substantial for IHC-PRGS (α = 0.69, 95% confidence interval [CI] = 0.66-0.72) and moderate for H&E-PRGS (α = 0.60, 95% CI = 0.56-0.64). Agreement (all raters) regarding the mean PRGS per QB set after treatment was higher for IHC-PRGS (α = 0.78, 95% CI = 0.73-0.83) than for H&E-PRGS (α = 0.71, 95% CI = 0.64-0.78). Among residents, agreement was almost perfect for IHC-PRGS and substantial for H&E-PRGS. Agreement (all raters) regarding maximum PRGS per QB set after treatment was substantial for IHC-PRGS (α = 0.61, 95% CI = 0.54-0.68) and moderate for H&E-PRGS (α = 0.60, 95% CI = 0.53-0.66). Among residents, agreement was substantial for IHC-PRGS (α = 0.66, 95% CI = 0.57-0.75) and moderate for H&E-PRGS (α = 0.55, 95% CI = 0.45-0.64). Additional IHC seems to improve the interobserver agreement of PRGS, particularly between less experienced raters.

IgG4-Related Sclerosing Cholangitis Involving the Intrahepatic Bile Ducts Diagnosed with Liver Biopsy.

IgG4-related disease is characterized by lymphoplasmacytic inflammation and fibrosis, often leading to mass-forming lesions in different organs. When IgG4-related disease affects the bile ducts, it is called IgG4-related sclerosing cholangitis. A 74-year-old male complained of dysphagia and abdominal pain. Endoscopic retrograde cholangiography and magnetic resonance cholangiography revealed bile duct changes suspicious of a bile duct carcinoma or cholangitis. Liver biopsy showed storiform fibrosis, lymphoplasmacytic infiltration, obliterative phlebitis, and a portal-based inflammatory nodule with expansion of a portal tract. Hot spots revealed 339 IgG4-positive cells per high power field (HPF) and an IgG4/IgG ratio of 72%. Eight months earlier, an inguinal lymph node had been removed, showing expanded interfollicular zones and increased plasma cells. Hot spots revealed 593 IgG4-positive cells and an IgG4/IgG ratio of 92%. The serum IgG4 of the patient was elevated nearly 10 times upper limit of normal. The diagnosis of IgG4-related sclerosing cholangitis associated with IgG4-related lymphadenopathy was made. There was good response to treatment with prednisolone and azathioprine. The differentiation of IgG4-related sclerosing cholangitis from primary sclerosing cholangitis and bile duct carcinoma is often difficult. Liver biopsy only rarely contributes to this setting, but we describe and report in detail a case where liver biopsy showed a portal-based inflammatory nodule with the characteristic features of this disease.