Vrana, Julie A.

Abstract Objective The aim of this study was to evaluate a large cohort of gallbladder amyloid cases to determine clinical and morphologic features. Methods Cholecystectomy specimens (N = 118) typed using proteomics-based techniques between 2008 and 2023 were identified. Clinical and morphologic features were reviewed. Results Six amyloid types were identified: ATTR (n = 63, 53.4%), AL (n = 46, 39.0%), AA (n = 4, 3.4%), AApoA1 (n = 2, 1.7%), ALECT2 (n = 2, 1.7%), and AEFEMP1 (n = 1, 0.8%). Amyloidogenic mutations were detected in 3 ATTR cases and 2 AApoA1 cases. Morphologic review (n = 26) revealed perimuscular vessel involvement in all cases. Amyloidosis was an unexpected diagnosis first made on the cholecystectomy specimen in half of the patients with clinical information (n = 10). All 9 patients with follow-up had evidence of systemic disease. In 2 patients, cholecystic involvement was initially missed and only retrospectively identified after the diagnosis of cardiac amyloidosis. Conclusions In patients with clinical data, amyloidosis was often unexpected, the gallbladder was commonly the first tissue sampled with amyloidosis, and all patients had systemic disease. Thorough review of cholecystectomy specimens with careful inspection of perimuscular vessels, coupled with a low threshold for ordering Congo red stain in elderly individuals and amyloid typing using a robust method such as proteomics, can prevent a delay in amyloid diagnosis and management.

e20646 Background: Thymic carcinomas tend to be aggressive malignancies with variable patterns of immunostaining. We aimed to assess whether the outcome of patients with thymic carcinomas was associated with immunoreactivity for conventional and emerging immunohistochemical markers of thymic carcinoma versus thymoma. Methods: Scoring of CD5, CD117, EZH2, POU2F3, BAP1, and MTAP immunohistochemistry on whole slide sections was compared to overall survival (OS) and progression free survival (PFS) for 36 thymic carcinoma patients, 28 of whom had complete tumor resection and 8 of whom had incomplete tumor resection. Results: Positive CD5 staining (defined as staining in ≥50% of tumor cells) was present in 13/36 cases (36%) and was significantly associated with longer OS (P = 0.005, hazard ratio = 0.18, CI 0.03-0.63) but not PFS (P = 0.14, hazard ratio = 0.48, CI 0.16-1.26), whereas the other markers were not significantly associated with OS or PFS. Positive CD5 staining remained significantly associated with OS in squamous cell carcinoma subgroup analysis (n = 23, HR = 0.17, CI 0.03-0.65, P = 0.009), patients who did not receive neo-adjuvant treatment (n = 24, HR = 0.21, CI 0.03-0.85, P = 0.03) and after adjusting for incomplete resection (HR = 0.20, CI0.03-0.73, P = 0.01), M1 stage (HR = 0.19, CI 0.03-0.71, P = 0.01) or neoadjuvant treatment (HR = 0.19, CI 0.03-0.71, P = 0.01) in bivariate models. Positive CD5 staining was also significantly associated with age ≥60 years, absence of neoadjuvant treatment, and positive POU2F3 staining. Conclusions: CD5 staining in ≥50% of tumor cells was significantly associated with longer OS for thymic carcinoma patients. Our study supports the notion that CD5 immunohistochemistry may have utility as a prognostic marker for thymic carcinomas.

Thymic carcinoma is an aggressive malignancy that can be challenging to distinguish from thymoma using histomorphology. We assessed two emerging markers for these entities, EZH2 and POU2F3, and compared them with conventional immunostains. Whole slide sections of 37 thymic carcinomas, 23 type A thymomas, 13 type B3 thymomas, and 8 micronodular thymomas with lymphoid stroma (MNTLS) were immunostained for EZH2, POU2F3, CD117, CD5, TdT, BAP1, and MTAP. POU2F3 (≥10% hotspot staining), CD117, and CD5 showed 100% specificity for thymic carcinoma versus thymoma with 51%, 86%, and 35% sensitivity, respectively, for thymic carcinoma. All POU2F3 positive cases were also positive for CD117. All thymic carcinomas showed >10% EZH2 staining. EZH2 (≥80% staining) had a sensitivity of 81% for thymic carcinoma and a specificity of 100% for thymic carcinoma versus type A thymoma and MNTLS but had poor specificity (46%) for thymic carcinoma versus B3 thymoma. Adding EZH2 to a panel of CD117, TdT, BAP1, and MTAP increased cases with informative results from 67/81 (83%) to 77/81 (95%). Overall, absent EZH2 staining may be useful for excluding thymic carcinoma, diffuse EZH2 staining may help to exclude type A thymoma and MNTLS, and ≥10% POU2F3 staining has excellent specificity for thymic carcinoma versus thymoma.

Abstract Introduction/Objective Amyloidosis encompasses a heterogeneous group of disorders characterized by abnormal deposition of misfolded proteins leading to progressive organ failure. Accurate amyloid typing is essential for proper patient management, as treatment regimens vary dramatically across different types. Bone marrow (BM) biopsy, in conjunction with fat pad aspiration/biopsy, is often the first step in patients with suspected amyloidosis. Although BM involvement by AL amyloid has been previously characterized, little is known about the incidence, morphology and clinical phenotype of non-AL amyloid in BM. Methods/Case Report We retrospectively identified 1469 BM biopsies by querying our reference laboratory database of 19,298 specimens from myriad anatomic sites typed by mass spectrometry-based proteomics (LC-MS/MS). These were reviewed for frequency of amyloid types (N=1469), distribution of amyloid deposits (N=139), and clinical phenotypes (N=345), with particular emphases on cardiac involvement. Results (if a Case Study enter NA) We identified the following amyloid types: AL (N=1172; 79.8%), ATTR (transthyretin) (N=240; 16.3%), AH (immunoglobulin heavy chain) (N=38; 2.6%), AA (serum amyloid A) (N=17; 1.2%), and Aβ2M (β2-microglobulin) (N=2; 0.1%). ATTR deposits showed striking predilection for periosteal soft tissue and/or periosteal vessels, and rarely involved BM stroma and/or interstitial vessels, while AL variably involved these compartments. AA primarily involved interstitial vessels. Both AL and ATTR cases commonly had a monoclonal gammopathy (AL: 92.9%; ATTR: 62.5%) with concomitant cardiac amyloidosis (AL: 91.6%; ATTR: 100%). Compared to AL, ATTR patients had higher stage cardiac amyloidosis and lower overall survival. Conclusion ATTR is common in BM, constituting16.3% of cases in our cohort. Rarer amyloid types, such as AA, AH and AB2M can also occur in BM. ATTR was frequently identified in patients with concomitant monoclonal gammopathy, in whom AL may have been suspected. Although ATTR deposits have distinctive morphologic distribution, primarily involving periosteal soft tissue and/or periosteal vessels and rarely involving BM stroma and/or interstitial vessels, there is considerable morphologic overlap with AL. Therefore, it is imperative to type BM amyloidosis, preferably by LC-MS/MS, to ensure proper patient management. Furthermore, BM involvement by ATTR may be a marker for advanced stage of disease.