<prompt> Mesothelioma is differentiated from adenocarcinoma by:Prescence of long slender microvilliAbundant altered mitochondriaRibosome clumpsDense secretory core granules  <response>: 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 primary2Malignant mesotheliomaMost common primaries from Lungs and Breast.Solitary fibrous tumour Benign mesotheliomaNo 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 CEA3 Staining for keratin proteins with accentuation of perinuclear rather than peripheral staining.4 Positive staining for calretinin, WT 1 susceptibility gene product, cytokeratin 56, 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 aw asbestos exposure isMalignant mesotheliomaMost common malignancy aw asbestos exposure isBronchogenic carcinoma. 