No single feature is characteristic of mesothelioma.

In more poorly differentiated mesotheliomas and adenocarcinomas there is some overlap of features.

Mesotheliomas are characterized by having long, narrow, branching microvilli with a length to width ratio of around 10-16:1

By contrast, adenocarcinomas have short, stubby microvilli with core rootlets.

Intermediate filaments are abundant and show perinuclear condensation in mesothelioma whereas they are less prominent in adenocarcinoma.

Electron microscopy can also be used to confirm the absence of features of adenocarcinoma, such as intracellular mucin and membrane-bound secretory granules. Zymogen vacuoles are not seen in mesothelioma and are useful indicator of adenocarcinoma.

Sarcomatoid and biphasic variants  show ultrastructural features transitional between epithelial and mesenchymal cells that will allow differentiation between mesothelioma and sarcoma or reactive fibroblasts.

Spindled cells of mesothelioma lack microvilli , but sometimes cells intermediate between epithelial and spindled with long microvilli can be found in predominantly spindled tumours.

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PULMONARY PATHOLOGY: Congenital Cystic Adenomatoid  Malformation ; Acute Respiratory Distress Syndrome  ;Sarcoidosis ;Bronchiolitis ; Emphysema ; Bronchial Asthma ;Chronic Bronchitis Pulmonary Alveolar Proteinosis ; Lipid Pneumonia ; Pulmonary Hypertension ;Pulmonary edema ;Pulmonary Infection ; Pneumococcal Pneumonia ; Haemophilus influenza Infection;Klebsiella Pneumoniae ; Mycoplasma Pneumonia ; Pneumocystis Pneumonia ; Legionellosis ; Localized Fibrous Tumour of the Pleura ; Biphasic Epithelial/Mesenchymal Lung Tumours ; Pulmonary Carcinosarcoma ;Pulmonary Blastoma ; Large Cell Neuroendocrine tumour;

Silicosis

Asbestosis

Coal Pneumoconiosis

Talcosis ;