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Interpretation of pleural biopsy specimens and aspirates with the immunoperoxidase technique
Abstract:
In pleural biopsy specimens and histological sections from the fibrin clots of pleural fluid aspirates it may be difficult to distinguish reactive mesothelial cells from malignant mesothelial cells and metastatic carcinoma. Reactive pleurisy with effusion is usually associated with loss of cohesion and exfoliation of mesothelial cells, which is consistent with the hypothesis that they act as facultative histiocytes. A series of biopsy specimens and sections of clots from benign and malignant pleural effusions have been stained by the immunoperoxidase technique for the histiocytic markers alpha 1-antitrypsin, alpha 1-antichymotrypsin, and lysozyme (muramidase). Eight cases of mesothelioma were included. Mesothelial cells when seen as a monolayer lining the pleural surface were negative. Reactive mesothelial cells, usually seen as exfoliated cells, were consistently strongly positive for alpha 1-antichymotrypsin and more variably for alpha 1-antitrypsin and lysozyme. Malignant cells, whether from carcinoma or from mesothelioma, were usually but not always negative. Consequently immunohistochemical staining for alpha 1-antichymotrypsin is often helpful in distinguishing reactive mesothelial cells from malignant cells.
Insights
Distinguishing reactive mesothelial cells from malignant cells in pleural effusions can be challenging. Immunohistochemical staining for alpha 1-antichymotrypsin is a helpful tool, as reactive cells are typically positive while malignant cells are often negative.
Area of Science:
- Pathology
- Cytology
- Immunohistochemistry
Background:
- Distinguishing reactive mesothelial cells from malignant cells in pleural biopsies and effusions is diagnostically challenging.
- Reactive mesothelial cells exhibit loss of cohesion and exfoliation, suggesting a histiocytic role.
Purpose of the Study:
- To evaluate the utility of histiocytic markers in differentiating reactive mesothelial cells from malignant cells in pleural specimens.
- To determine if immunohistochemical staining can aid in the diagnosis of pleural effusions.
Main Methods:
- Immunoperoxidase staining was performed on pleural biopsy specimens and fibrin clots from benign and malignant effusions.
- Histiocytic markers including alpha 1-antitrypsin, alpha 1-antichymotrypsin, and lysozyme (muramidase) were used.
- Eight cases of mesothelioma were included in the study.
Main Results:
- Normal mesothelial cells lining the pleura were negative for all markers.
- Reactive mesothelial cells were consistently positive for alpha 1-antichymotrypsin and variably positive for alpha 1-antitrypsin and lysozyme.
- Malignant cells (carcinoma and mesothelioma) were generally negative, though not always.
Conclusions:
- Immunohistochemical staining for alpha 1-antichymotrypsin is a valuable adjunct in distinguishing reactive mesothelial cells from malignant cells in pleural effusions.
- The differential expression of histiocytic markers can aid in the accurate diagnosis of pleural pathology.