In diffuse mesothelioma epithelial DMM are the most commonly diagnosed histologic type.
1. Tubulopapillary Pattern: Mixture of small tubules and papillary structures with fibrovascular cores, often with clefts and trabeculae. In Well differentiated tumours the fibrohyaline papillae are lined by neoplastic mesothelial cells -(uniformly cuboidal cells with large vesicular nuclei and prominent nucleoli ). Psammoma bodies may be present. Image Link
D/D: Adenocarcinoma metastatic to the pleura.
2. Acinar Pattern: Characterized by acinar or glandlike structures.
D/D: Metastatic adenocarcinoma.
3. Adenomatoid Pattern (also termed microglandular): Small gland-like structures lined by bland flat to cuboidal cells.
D/D: Metastatic adenocarcinoma.
4. Small cell pattern : Sheets of monotonous small hyperchromatic uniform cells with a high nucleocytoplasmic ratio.
D/D: This variant may mimic small cell carcinoma or lymphoma. Nuclear karyorrhexis and haematoxyphilic vessels are not a feature in mesothelioma . Lymphoma is distinguished from small cell variant of mesothelioma by immunohistochemical examination.
5. Deciduoid Pattern: Identified in the pleura of elderly patients. Histologically the tumour is characterized by proliferation of large, round to polygonal cells with sharp cell borders, abundant glassy eosinophilic cytoplasm, and round vesicular nuclei with prominent nucleoliRead More
