Mesothelioma is differentiated from adenocarcinoma by:

Ans a) (Prescence of long slender microvilli) Ref: Robbins 7th e p 768 - 69Malignant mesothelioma is characterized by microvilli which are numerous, long & slender whereas in pulmonary adenocarcinoma microvilli are short & plump.Pleural tumoursPrimary tumoursSecondary tumours1 )Solitary fibrous tumourMore common than primary2)Malignant mesotheliomaMost common primaries from Lungs and Breast.Solitary fibrous tumour ( Benign mesothelioma)No relationship to asbestos exposure.Usually will not produce pleural effusion.Tumour cells are CD34+ and keratin negative by immunostaining.Malignant mesotheliomaAssociated with exposure to asbestos but no increased risk of mesothelioma in asbestos workers who smoke.Cytogenetic abnormalitiesDeletion in lp, 3p, 6q, 9p, or 22q in 60% - 80% cases.P53 mutation seen in 70% malignant mesotheliomas.SV 40 DNA sequences in 60 - 80% Malignant mesothelioma.Differentiating points between Malignant mesothelioma & Pul, adenocarcinomaFeatutes favouring mesothelioma arej.1) Positive staining for acid mucopolysaccharide.2) Lack of staining for carcinoembryonic antigen( CEA)3) Staining for keratin proteins with accentuation of perinuclear rather than peripheral staining.4) Positive staining for calretinin, WT 1 susceptibility gene product, cytokeratin 5/6, mesothelin, and thrombomodulin5) Presence of long, slender microvilli and abundant tonofilaments but absent microvillous rootlets & lamellar bodies.RememberMesotheliomas can also arise from peritoneum, pericardium, tunica vaginalis and Genital tract.Most specific malignancy a/w asbestos exposure isMalignant mesotheliomaMost common malignancy a/w asbestos exposure isBronchogenic carcinoma.