Kouki Inai’s research while affiliated with Hiroshima University and other places

In breast cancer surgery, some medical facilities lack the necessary resources to conduct sentinel lymph node biopsy and its intraoperative frozen section consultation. In the coastal rural area of Fukushima, Japan, which has suffered from physician undersupply following the 2011 triple disaster of earthquake, tsunami and nuclear disaster, we explored the feasibility of telepathology by evaluating the diagnostic accuracy in remote intraoperative frozen section consultation of sentinel lymph node biopsy and its required time. Although examination time has room for improvement, telepathology can be one possible solution in resource-limited areas.

Background Anatomical pathology care services play an essential role in cancer diagnosis through histological analysis, effective treatment of patients, and determination of prognosis. Therefore, quality control is necessary for the diagnosis of pathology. Based on this need, telepathology technology is rapidly developing in the world. This study aimed to share the experience of implementing telepathology case consultation between Mongolian and Japanese expert pathologists. Methods The study included 173 cases that required telepathology consultation, which was complicated and doubtful in diagnosis, submitted by Mongolian pathologists between May 2019 and April 2022. The scanned digital slides were transmitted with the help of the LOOKREC cloud-based system, and the expert pathologists of Hiroshima University Hospital, Japan, browsed the images through the data on the internet and their advice and made a mutual diagnosis. Results During the study period, 173 cases were consulted. Out of 58.4% of all cases, consultation reports were released in 2022. The majority of the cases in 2020 had a mean standard deviation turn-around time of 4.2±6.2 days. The most cases were from the lung and mediastinum were 29.4%, followed by head and neck at 12.6%, the bone at 11.9%, lymph nodes at 8.4%, GIT at 7.7%, soft tissues at 6.3%, etc. Comparing the sample submission of biopsy and cytology was significantly higher in the under 10 years of an experienced group than over 10 years of an experienced group (p<.005). The diagnostic agreement between submitter Mongolian pathologists and expert Japanese pathologists was 82.7%, and disagreement was 17.3% of all cases, with a sensitivity of 67.3% and specificity of 85.5%. Conclusions Telepathology could save many lost opportunities and play an essential role in developing quality control and surgical pathology in Mongolia. This digital technology and the appropriate strategy and policy of the government could accelerate the overall pathology field development.

Although the routine use of immunohistochemistry has improved the accuracy of histopathologic diagnosis in clinical practice, new methods for discovering novel diagnostic markers are still needed. We sought new diagnostic markers for malignant pleural mesothelioma (MPM) using a reverse translational approach with limited archival tissues from a very rare case. Total RNA extracted from formalin-fixed paraffin-embedded (FFPE) tissues of a synchronous collision tumor consisting of MPM and pulmonary adenocarcinoma (PAC) was employed for gene expression profiling (GEP) analysis. Among the 54 genes selected by GEP analysis, we finally identified the following two candidate MPM marker genes: PHGDH and TRIM29. Immunohistochemical analysis of 48 MM and 20 PAC cases showed that both PHGDH and TRIM29 had sensitivity and specificity almost equivalent to those of calretinin (sensitivity 50% and 46% vs. 63%, and specificity 95% and 100% vs. 100%, respectively). Importantly, of the 23 epithelioid MMs, all 3 calretinin-negative cases were positive for TRIM29. These two markers may be diagnostically useful for immunohistochemical distinction between MPMs and PACs. This successful reverse translational approach based on FFPE samples from one very rare case encourages the further use of such samples for the development of novel diagnostic markers.

Histological distinction between epithelioid mesothelioma (EM) and reactive mesothelial hyperplasia (RMH) can be challenging. The aim of this study was to assess the diagnostic utility of Survivin, Ki-67, and loss of BRCA1-associated protein 1 (BAP1) expressions in distinguishing EM from RMH using immunohistochemistry. Formalin‑fixed, paraffin‑embedded specimens from 78 cases of EM and 80 cases of RMH were immunohistochemically examined for Survivin, BAP1, and Ki-67. In addition, receiver operating characteristic curve analyses were performed to establish the cut-off values for Survivin and Ki-67 labelling indices. Survivin (cut-off value: 5%) had 67.7% sensitivity and 100% specificity, while Ki‑67 (cut‑off value: 10%) had 85.1% sensitivity and 87.5% specificity, and BAP1 had 66.2% sensitivity and 100% specificity for the differentiation of EM from RMH. Among the combinations of two markers, the combination of Survivin and BAP1 (Survivin-positive and/or BAP1‑loss finding) had the highest diagnostic accuracy (sensitivity: 89.8%; specificity: 100%; accuracy: 95.3%). We recommend using the combination of Survivin and BAP1 to distinguish EM from RMH.

Background The differential diagnosis between epithelioid mesothelioma (EM) showing a solid histological pattern (solid EM) and poorly differentiated squamous cell carcinoma (SCC) can be challenging with conventional light microscopy (haematoxylin and eosin-stained specimen) alone. The role of immunohistochemistry in distinguishing pleural EM from lung adenocarcinoma (LAC) has received much attention. Currently, many immunohistochemical markers are available for distinguishing pleural EM from LAC. . However, there are only a few reports on the immunohistochemical differential diagnosis of EM and lung SCC. Ordonez et al. have reported the immunohistochemical analyzes of 30 EMs showing a solid pattern and 30 pulmonary non-keratinizing SCCs, and have recommended the combination of two positive (Wilms' tumor gene product; WT1 and calretinin/mesothelin) and two negative (p63 and Epithelial-related antigen; MOC31) markers for differentiating EM from lung SCC. The aims of this study were to clarify the usefulness of immunohistochemistry in the differential diagnosis of solid EM and poorly differentiated SCC, and to confirm the validity of a specific type of antibody panel. Additionally, we aimed to clarify the pitfalls of immunohistochemical analyzes. Method Formalin-fixed paraffin-embedded specimens from 36 cases of solid EM and 38 cases of poorly differentiated SCC were immunohistochemically examined for calretinin, podoplanin (D2-40), WT1, cytokeratin (CK) 5/6, p40, p63, carcinoembryonic antigen (CEA), MOC31, claudin-4, thyroid transcription factor-1 (TTF-1), and napsin A. Result WT1 showed the highest diagnostic accuracy (85.1%) as a mesothelial marker, and CEA, p40 and claudin-4 showed higher diagnostic accuracy (95.9%, 94.6%, and 93.2%, respectively) as carcinoma markers. Calretinin (diagnostic accuracy: 75.7%), D2-40 (diagnostic accuracy: 67.6%), CK5/6 (diagnostic accuracy: 63.5%), TTF-1 (diagnostic accuracy: 55.4%) and napsin A (diagnostic accuracy: 52.7%) could not differentiate between solid EM and poorly differentiated SCC. Among these markers, the combination of calretinin and WT1 showed the highest diagnostic accuracy (86.5%) as a positive marker, and the combination of p40 and CEA showed the highest diagnostic accuracy (97.3%) as a negative marker. The combination of CEA and claudin-4 also showed relatively high diagnostic accuracy (94.6%) as a negative marker. Conclusion We recommend the combination of WT1 and calretinin as a positive maker, and the combination of CEA and claudin-4 as a negative marker, for differential diagnoses of solid EM and poorly differentiated SCC. Keywords Mesothelioma, Squamous cell carcinoma, Immunohistochemistry

Background Malignant mesothelioma is a fatal malignant tumor. It is often difficult to diagnose and to differentiate from other carcinomas, especially pulmonary adenocarcinoma. As there are currently no absolute immunohistochemical positive markers for the definite diagnosis of epithelioid mesothelioma, the identification of additional “positive” markers that may facilitate this diagnosis becomes of clinical importance. Method Gene Expression Analysis Formalin-fixed paraffin-embedded tissue sections from 6 epithelioid mesothelioma and 6 pulmonary adenocarcinoma cases were used for gene expression analysis. RNA extraction for gene expression analysis was performed from papillary or solid growth of tumor cells in each specimen. The Human Transcriptome 2.0 GeneChip Array containing gene transcript sets of 44,699 protein coding and 22,829 nonprotein coding clusters was used to analyze gene expression profiles. Validation by Real-time RT PCR & Western Blotting The increased mRNA expression of DAB2 and Intelectin-1 was validated by reverse transcriptase polymerase chain reaction of RNA from tumor tissue and protein expression was validated by Western blotting of 5 mesothelioma cell lines. Immunohistochemical Procedures and Evaluation of Expression of DAB2 and Intelectin-1 The utility of DAB2 and Intelectin-1 in the differential diagnosis of epithelioid mesothelioma and pulmonary adenocarcinoma was examined by an immunohistochemical study of 75 cases of epithelioid mesothelioma and 67 cases of pulmonary adenocarcinoma. Result Differential Gene Expression Of the 44,699 protein coding and 22,829 nonprotein coding transcripts on the Human Transcriptome 2.0 GeneChip Array, 902 statistically significant mRNA transcripts were differentially expressed, with a greater than 1.3-fold difference, between epithelioid mesothelioma and pulmonary adenocarcinoma. Validation Realtime RT-PCR showed relative mRNA expression of DAB2 and Intelectin-1 was significantly higher in epithelioid mesothelioma than that in pulmonary adenocarcinoma. Western blot analysis showed DAB2 and Intelectin-1 protein expression in all 5 commercially available mesothelioma cells lines with anti-DAB2 and anti-Intelectin-1 antibody. Immunohistochemical Expression Profiles in Epithelioid Mesothelioma and Pulmonary Adenocarcinoma The expression of DAB2 and Intelectin-1 was localized in the cytoplasm of tumor cells in epithelioid mesothelioma cases. Positive DAB2 expression was observed in 60 of 75 epithelioid mesotheliomas (80.0%) and 2 of 67 pulmonary adenocarcinomas (3.0%). In half of epithelioid mesotheliomas, DAB2 immunoreactivity was generally strong and diffuse (score 3+). In contrast, pulmonary adenocarcinomas showing DAB2 expression was focal (score 1+). Conclusion We identified 2 novel positive markers of epithelioid mesothelioma, DAB2 and Intelectin-1, by using gene expression microarray analysis and confirmed their utility to differentiate epithelioid mesothelioma from pulmonary adenocarcinoma by immunohistochemical study. Keywords DAB2 & Intelectin-1, Epithelioid mesothelioma, gene expression analysis

As there are currently no absolute immunohistochemical positive markers for the definite diagnosis of malignant epithelioid mesothelioma, the identification of additional "positive" markers that may facilitate this diagnosis becomes of clinical importance. Therefore, the aim of this study was to identify novel positive markers of malignant mesothelioma. Whole genome gene expression analysis was performed using RNA extracted from formalin-fixed paraffin-embedded tissue sections of epithelioid mesothelioma and pulmonary adenocarcinoma. Gene expression analysis revealed that disabled homolog 2 (DAB2) and Intelectin-1 had significantly higher expression in epithelioid mesothelioma compared with that in pulmonary adenocarcinoma. The increased mRNA expression of DAB2 and Intelectin-1 was validated by reverse transcriptase polymerase chain reaction of RNA from tumor tissue and protein expression was validated by Western blotting of 5 mesothelioma cell lines. The utility of DAB2 and Intelectin-1 in the differential diagnosis of epithelioid mesothelioma and pulmonary adenocarcinoma was examined by an immunohistochemical study of 75 cases of epithelioid mesothelioma and 67 cases of pulmonary adenocarcinoma. The positive rates of DAB2 and Intelectin-1 expression in epithelioid mesothelioma were 80.0% and 76.0%, respectively, and 3.0% and 0%, respectively, in pulmonary adenocarcinoma. Immunohistochemically, the sensitivity and specificity of DAB2 was 80% and 97% and those of Intelectin-1 were 76% and 100% for differentiation of epithelioid mesothelioma from pulmonary adenocarcinoma. In conclusion, DAB2 and Intelectin-1 are newly identified positive markers of mesothelioma and have potential to be included in future immunohistochemical marker panels for differentiation of epithelioid mesothelioma from pulmonary adenocarcinoma.