# A Case of Mesothelial‐Cell Inclusions in the Mediastinal Lymph Nodes After Lung Cancer Surgery

## TL;DR

This paper reports the first case of mesothelial-cell inclusions in mediastinal lymph nodes after lung cancer surgery, highlighting the importance of distinguishing it from metastasis to avoid misdiagnosis.

## Contribution

The paper presents the first documented case of MCI after lung cancer surgery.

## Key findings

- An enlarged lymph node was resected and diagnosed as MCI through histopathology and immunohistochemistry.
- Immunohistochemical markers confirmed the mesothelial origin of the cells.
- The case emphasizes the need to consider MCI in the differential diagnosis of post-surgery lymph node enlargement.

## Abstract

Mesothelial‐cell inclusion (MCI) is an inclusion of mesothelial cells found in lymph nodes. Although it is a rare condition, differentiating it from lymph node metastasis is essential to avoid a misdiagnosis. We reported, for the first time, a case of MCI after lung cancer surgery. The patient was a 76‐year‐old Japanese man with a history of bilateral radical surgery for lung cancer. Follow‐up computed tomography performed at 7 years after the initial surgery revealed an enlarged right cardiophrenic angle lymph node. It was resected through video‐assisted thoracic surgery, and histopathology revealed non‐dysplastic ductal proliferation. Immunohistochemistry was positive for AE1/3, D2‐40, calretinin, and WT‐1, and negative for CD31, CD34, and factor VIII. Based on these findings, MCI was finally diagnosed. Although the presence of metastasis is the first possible cause for the enlarged lymph nodes in such cases, MCI must also be considered.

We reported, for the first time, a case of mesothelial‐cell inclusion (MCI) after lung cancer surgery.