Differential Diagnosis

• Single most likely diagnosis:
  • Benign reactive mesothelial cells: The presence of cohesive clusters and singles of reactive mesothelial cells with smooth borders, occasional windows, mild anisocytosis, fine chromatin, and inconspicuous nucleoli is highly suggestive of a benign reactive process, often seen in response to injury or inflammation in the pleural or peritoneal space.
• Other Likely diagnoses:
  • Chronic inflammation: The proteinaceous background with scattered small lymphocytes and macrophages could indicate a chronic inflammatory process, which might be related to a variety of conditions including infection, autoimmune disease, or a reaction to a foreign body.
  • Serous effusion: The description is also consistent with a benign serous effusion, which can occur in the pleural, pericardial, or peritoneal spaces due to various causes including heart failure, liver cirrhosis, or nephrotic syndrome.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • Malignant mesothelioma: Although the description suggests a benign process, it is crucial not to miss the possibility of malignant mesothelioma, a rare but aggressive cancer associated with asbestos exposure. The presence of mesothelial cells with atypical features would necessitate further investigation.
  • Metastatic adenocarcinoma: It is also important to consider the possibility of metastatic adenocarcinoma, especially if there is a known history of cancer. While the description does not strongly suggest this diagnosis, certain types of adenocarcinoma can mimic mesothelial cells, and missing this diagnosis could have significant implications.
• Rare diagnoses:
  • Mesothelial hyperplasia: This is a rare condition characterized by an increased number of mesothelial cells, which can sometimes be difficult to distinguish from malignant mesothelioma. The clinical context and further diagnostic tests would be necessary to make this diagnosis.
  • Well-differentiated papillary mesothelioma: A rare, borderline malignant tumor that can present with similar cytological features. It tends to have a better prognosis than malignant mesothelioma but requires thorough evaluation to confirm the diagnosis.