In a 70-year old man who was working in an asbestos factory for 10-15 years. On routine X-ray. a mass was seen in the right apical region of the lung. Biopsy w s taken from the mass. Which of the following is seen on electron microscopic examination?(AIIMS November 2014, November 2013)
Ans. a. Numerous long, slender microvilli {Ref. Robbin's 8/e p669 734)In a 70 years old man, who is working in an asbestos factory for 10-15 years. On routine X-ray, a mass was seen in the right apical region of the lung. A biopsy was taken from the mass. Most likely diagnosis on the basis of description is malignant mesothelioma. Numerous long, slender microvilli will be seen on electron microscopy in malignant mesothelioma. (AllMS November 2013 repeat)Diagnosis depends on a constellation of findings, including the history of asbestos exposure, clinical signs and symptoms, radiographic findings, histopathological features, and immunohistochemical and ultrastructural studies. On electron microscopy, the presence of long microvilli and abundant tonofilaments but absent microvillous rootlets and lamella bodies favor the diagnosis of malignant mesothelioma. Electron microscopy (ultrastructural examination) has been accepted for many years as the 'gold standard' for the diagnosis of mesothelioma. Mesothelioma cells are characterized by a profusion of markedly elongated surface microvilli in the absence of secretory cytoplasmic granules. Robbin's 8/e p734Mesotheliomas:Most specific neoplasm associated with asbestosisMay develop 1-2 years after exposure, but incidence peaks at 20-35 years of exposureShows strong male predilection (3:1)Diagnosis depends on a constellation of findings, including the history of asbestos exposure, clinical signs and symptoms, radiographic findings, histopathological features, and immunohistochemical and ultrastructural studies.On electron microscopy, the presence of long microvilli and abundant tonofilaments but absent microvillous rootlets and lamella bodies favor the diagnosis of malignant mesothelioma.Pathological Features of Malignant MesotheliomaMalignant mesothelioma is a diffuse lesion that spreads widely in the pleural spaceUsually associated with extensive pleural effusion and direct invasion of thoracic structures.The affected lung becomes ensheathed by a thick layer of soft, gelatinous, grayish pink tumor tissue.Microscopically, malignant mesotheliomas may be epithelioid (60%), sarcomatoid (20%), or mixed (20%).Epithelioid mesotheliomaEpithelioid mesothelioma may at times be difficult to differentiate grossly and histologically from pulmonary adenocarcinoma. Features that favor mesothelioma includes:Positive staining for acid mucopolysaccharide, which is inhibited by previous digestion by hyaluronidaseLack of staining for CEA and other epithelial glycoprotein antigens, markers that are generally expressed by adenocarcinomaStrong staining for keratin proteins, with accentuation of perinuclear rather than peripheral stainingPositive staining for calretinin, Wilms tumor 1 (WT-1), cytokeratin 5/6, and D2-40On electron microscopy. the presence of Iona microvilli and abundant tonofilaments but absent microvillous rootlets and lamellar bodies.The mesenchymal type of mesothelioma appears as a spindle cell sarcoma, resembling fibrosarcoma (sarcomatoid type).The mixed type of mesothelioma contains both epithelioid and sarcomatoid patterns. Asbestos-Related Lung DiseasePulmonaryPleuralBenignMalignantBenignMalignant* Diffuse interstitial fibrosis (Asbestosis is defined as a diffuse interstitial fibrosing disease of the lung caused by exposure to asbestos fibers)* Bronchogenic carcinoma (All histological subtypes of lung cancer occur with increased frequency but Adenocarcinoma has the highest incidence)* Pleural plaques* Diffuse pleural thickening* Acute benign pleural effusion* Rounded atelectasis* Mesothelioma (Both pleural and peritoneal mesothelioma* develop in persons exposed to asbestos)
Numerous long, slender microvilli
Neurosecretory granules in the cytoplasm
Melanosomes
Desmosomes