Higher PD-L1 Immunohistochemical Detection Signal in Frozen Compared to Matched Paraffin-Embedded Formalin-Fixed Tissues

Purpose: Response to anti-PD-L1/PD-1 immunotherapy correlates with PD-L1 expression in breast cancer. However, the prevalence of PD-L1 positive breast cancer is variable, which could be due to differences in the population/cohort of patients tested or the preservation/detection technology used. To investigate this variability, we examined the effect of two tissue preservation methods on PD-L1 immunohistochemical detection in breast cancer. Methods: We compared PD-L1 expression in patient-matched frozen (FR) and formalin-fixed paraffin-embedded (FFPE) tissues of breast cancer patients. PD-L1 expression was assessed using tumor proportion score (TPS, simply PD-L1 score), and case positivity was determined with PD-L1 score ≥5. Results: In FFPE tissues, PD-L1 was positive in 7–10% of tested patients, depending on the antibody used. In patient-matched FR tissues, the same antibodies showed positive PD-L1 expression in 20–30% of cases. The impact of the antibody tested on the rate of PD-L1 positivity (% of PDL1 positive cases) was minor, as evident in the near perfect concordance between PD-L1 score obtained using the different antibodies whether tested in FR or FFPE tissues. However, there was a systematic drop by an average of 13–20% in the PD-L1 score obtained in FFPE tissues compared to their patient-matched FR tissues. Conclusions: In the tested patient-matched cohort, there was consistently a higher PD-L1 score in FR than FFPE tissues, regardless of the antibody used, demonstrating a significant effect on PD-L1 detection due to the preservation method. These findings should inspire further work to improve the sensitivity of PD-L1 detection and possibly search for more sensitive antibodies in FFPE tissues.

Blastic Plasmacytoid Dendritic Cell Neoplasm With Skin and Bone Marrow Involvement:three Case Reports and Literature Reviews

Background Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and highly aggressive hematopoietic malignancy. BPDCN is difficult to diagnose because of the overlap in morphologic and immunophenotypic features with various cutaneous lymphatic hematopoietic tumors. Case presentation All cases were characterized by skin nodules and examined by histology, immunohistochemical detection, in situ hybridization for Epstein -Barr virus, and follow-up, and the relevant literatures were reviewd. Two patients involved the bone marrow. Immunohistochemical detection showed CD56 were positive, EBER were negative. Chemotherapy is the main treatment for BPDCN, but case 1 showed bone marrow suppression; and case 2 developed recur after chemotherapy. Conclusions An accurate pathological diagnosis is a precondition for treatment, and the diagnosis of BPDCN should be based on a combination of clinical symptoms, pathological characteristics, immunophenotype, and other auxiliary examinations. It is necessary to clarify the clinicopathological features and biological behavior of BPDCN to improve the understanding of BPDCN by both clinicians and pathologists. A cytotoxin directed against CD123(tagraxofusp) may bring new future.

Optimized Immunohistochemical Detection of Rat ESR2 Proteins Using the Specific Anti-ESR2 Monoclonal Antibody PPZ0506

Background: Research on ESR2, also known as estrogen receptor β (ERβ), is a notorious example of data distortion due to the use of inadequately validated antibodies. Although the absence of reliable specific antibodies against ESR2 has severely hindered the promotion of ESR2 research, a specific anti-human ESR2 monoclonal antibody (PPZ0506) was identified in 2017 [1]. Our previous study confirmed its cross-reactivity and specificity against rodent ESR2 proteins, enabling the elucidation of the true ESR2 distribution in rodents [2]. Objective: We aimed to determine the optimized conditions for immunohistochemical detection of rat ESR2 proteins using PPZ0506. <Method> Several staining conditions using paraffin-embedded and frozen ovary sections were evaluated, and the distribution of rat ESR2 proteins was analyzed under optimal conditions. Result: Immunohistochemical staining with PPZ0506 required appropriate antigen retrieval and antibody dilution. Subsequent immunohistochemical analysis in multiple tissues under optimized conditions revealed that rat ESR2 proteins are expressed in a more localized manner than previously assumed. Our optimized immunohistochemical detection of rat ESR2 proteins, using a well-validated antibody, revealed their distribution in limited tissues and cell types. Conclusion: Our results suggest that previous immunohistochemical studies using inadequately validated antibodies against ESR2 proteins overestimated their distribution profiles. We expect that our optimized immunohistochemistry using the PPZ0506 antibody may solve conflicting problems in ESR2 research. References: 1. Andersson S, et al. Nat Commun 15;8:15840 (2017) 2. Ishii H, et al. Int J Mol Sci 20(24):6312 (2019)