updated research on calretinin immunohistological marker staining and ultrastructural verification of some cases of epitheliod malignant mesothelioma

ABSTRACT

Diagnosis of malignant mesothelioma is frequently a difficult problem for clinicians and pathologists alike. The diagnosis of malignant mesothelioma is dependent on assessment of clinical and radiological findings in conjunction with pleural fluid cytology and pleural biopsy. Immunohistochemical stains have proved most useful in most cases, but despite many antibodies showing potential, it is generally agreed that no one antibody shows absolute specificity or sensitivity for either tumor. Electron microscopy [EM] has been a classic gold standard tool used to confirm or identify mesothelial differentiation either focal or wide spread in most cases. However, prospective studies, which address the diagnostic accuracy of EM through a long series of unselected, clinically well- documented mesotheliomas, are lacking. Poorly differentiated cases need combinations of a mucin stain, IHC, and EM examination to confirm their mesothelial origin. Retrospective 15 cases of epitheliod mesothelioma were selected from the files of Pathology Department, Faculty of Medicine, Alexandria University; 10 cases were CT-guided needle biopsies and 5 cases were surgical specimens. Histopathological examination by routine stain using H and E revealed tumour cells showing staining by PASD was negative in all pleural cases and focally positive in the peritoneal case. Immunohistochemical staining by anti - calretinin showed 13 positive cases with nuclear and cytoplasmic brown staining [86.6%], one case / 15 [6.6%] was score 1,4 cases / 15 [26.66%] were score 2 and 8 cases / 15 [53.33%] were score 3. The 2 negatively - stained cases [13.3%] were subjected to further examination by EM. The micrographs showed tiny intracytoplasmic lumina having a microvillous border. The microvilli appeared long slender and curved disclosing their mesothelial origin