Diagnostic Utility of Podoplanin Immunohistochemistry Combined with the NanoSuit-Correlative Light and Electron Microscopy Method for Thoracic Malignant Tumors

Our plain-English summary of Diagnostic Utility of Podoplanin Immunohistochemistry Combined with the NanoSuit-Correlative Light and Electron Microscopy Method for Thoracic Malignant Tumors, by S.Y. Katsuragi, Y. Sakano, I. Ohta, et al (Diagnostics, 2025).

The study

• Authors: S.Y. Katsuragi, Y. Sakano, I. Ohta, H. Kato, R. Ishikawa, H. Watanabe, R. Miyazaki, K. Yoshimura, H. Yamada, Y. Sakai, Y. Inoue, Y. Takanashi, K. Sekihara, K. Funai, Y. Otsuki, H. Kawasaki, K. Shinmura
• Journal: Diagnostics
• Published: 2025;15(10)
• Read it: PubMed · Publisher · Free full text

Abstract

Background/Objectives: Differentiating thoracic malignant tumors, such as epithelioid malignant pleural mesothelioma (EMPM) and non-small-cell lung carcinoma (NSCLC), primarily comprising lung adenocarcinoma (LAC) and lung squamous cell carcinoma (LSCC), remains a challenge in routine pathological diagnosis. This study aimed to evaluate whether podoplanin (PDPN) immunohistochemistry combined with scanning electron microscopy (SEM) using the NanoSuit-correlative light and electron microscopy (CLEM) methods could serve as a reliable tool for distinguishing these thoracic malignancies. Methods/Results: Initially, PDPN expression was assessed by immunohistochemical analysis in 11 EMPM, 100 LAC, and 23 LSCC cases. PDPN positivity was predominantly observed in the cell membrane and was significantly more frequent in EMPM (100%) than in LAC (2%; p < 0.0001) or LSCC (43.5%; p = 0.0018). Subsequently, field emission-SEM (FE-SEM) observations of PDPN-positive sites on immunohistochemical slides, conducted using the NanoSuit-CLEM method, revealed distinctive ultrastructural features. EMPM exhibited densely packed, elongated microvilli, whereas such structures were absent in LAC and LSCC. Furthermore, analysis of thick-cut sections (20 μm) demonstrated extensive microvilli coverage characteristic of EMPM. Conclusions: These findings suggest that the combined approach of PDPN immunohistochemistry and FE-SEM observation of PDPN-positive sites, using the NanoSuit-CLEM method, constitutes an effective diagnostic strategy for enhancing the accuracy of distinguishing EMPM from NSCLCs.

In plain English

This laboratory study, from Hamamatsu University School of Medicine in Japan, tested whether staining tissue for a protein called podoplanin, combined with a scanning electron microscope technique called NanoSuit-CLEM, could help pathologists tell epithelioid malignant pleural mesothelioma apart from two common lung cancers, lung adenocarcinoma and lung squamous cell carcinoma. It used archived tumor tissue from 11 mesothelioma, 100 adenocarcinoma and 23 squamous cell carcinoma cases. The study did not examine asbestos exposure. Podoplanin staining was positive in 11 of 11 mesotheliomas, compared with 2 of 100 adenocarcinomas (p less than 0.0001) and 10 of 23 squamous cell carcinomas (p = 0.0018). Under the electron microscope, the stained areas in three mesothelioma cases showed densely packed, thick, elongated microvilli, which are tiny finger-like projections on the cell surface. The authors reported that such well-developed microvilli were not seen in the lung cancer samples they examined. Thicker 20-micrometre sections showed whole mesothelioma cell surfaces covered with these projections. The authors concluded that the combined approach is effective for distinguishing this mesothelioma from these lung cancers. They noted that the small number of mesothelioma cases (11) means further validation is required.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective laboratory study of archived tumor tissue, using immunohistochemistry (podoplanin staining) followed by field emission scanning electron microscopy with the NanoSuit-CLEM method
• Who was studied: Archived tissue blocks from 11 primary epithelioid malignant pleural mesothelioma cases, 100 primary lung adenocarcinoma cases and 23 primary lung squamous cell carcinoma cases at Hamamatsu University Hospital, Japan. Electron microscopy images were shown for three mesothelioma cases and one case each of adenocarcinoma and squamous cell carcinoma.
• Exposure: Not studied. The study examined tumor tissue staining and microscopic structure. Asbestos is mentioned only in the introduction as the main association of this mesothelioma.
• Main results:
  • Podoplanin-positive tumor cells were found in 11/11 (100%) epithelioid malignant pleural mesotheliomas. This compared with 2/100 (2%) lung adenocarcinomas (p < 0.0001) and 10/23 (43.5%) lung squamous cell carcinomas (p = 0.0018).
  • Staining was relatively diffuse in mesothelioma but focal in the two lung cancer types.
  • In the lung adenocarcinoma and squamous cell carcinoma groups, podoplanin staining was not significantly associated with clinicopathological factors.
  • In three mesothelioma cases, the electron microscope showed densely packed, thick, elongated microvilli at the podoplanin-stained sites.
  • In the lung adenocarcinoma and squamous cell carcinoma samples, the stained areas showed what the authors called 'poorly nourished' microvilli. The authors stated that well-developed microvilli were not observed in these cancers.
  • In thick-cut (20 µm) sections, the whole surface of mesothelioma cells was covered with dense, elongated microvilli. Such structures were absent on squamous cell carcinoma cells.
• The authors' conclusion: The authors concluded that combining podoplanin immunohistochemistry with FE-SEM using the NanoSuit-CLEM method is an effective approach for distinguishing epithelioid malignant pleural mesothelioma from non-small-cell lung carcinomas. They proposed a diagnostic workflow in which cases negative for podoplanin would go on to conventional antibody panels.
• Limitations the authors state:
  • The number of mesothelioma cases was small (11), and further validation in a larger multi-institutional study is required.
  • The 3% cut-off used to call a tumor podoplanin-positive is not an established threshold for podoplanin.

Topics

Medical terms in this study, explained in our Lexicon: Podoplanin (D2-40), Immunohistochemistry, Epithelioid, Pleural Mesothelioma, Carcinoma, Lung Adenocarcinoma, Squamous Cell Carcinoma, Scanning Electron Microscopy (SEM).

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