Pseudomesotheliomatous Pleural Effusion

Diagnosis

Metastatic Large Cell Adenocarcinoma
with Type II Pneumocyte differentiation
and presenting as a pseuodmesotheliomatous pleural effusion.

Discussion

The ultrastructural findings demonstrated features of carcinoma cells with Type II Pneumocyte differentiation. The characteristic features of malignant mesothelioma, namely, abundant glycogen, perinuclear tonofilaments, and slender, thin, serpentine microvilli were not demonstrated at the ultrastructural level. Instead a distinct, finely granular glycocalyx, minute mucinous vesicles and immature osmiophilic, lamellar granules were demonstrated. These findings correlated with the marked elevations of CEA in the pleural fluid supernatant.

References:

1. Brown RW, Clark GM, Tandon AK and Allre DC.
   Multiple-marker immunohistochemical phenotypes distinguishing malignant pleural mesothelioma from pulmonary adenocarcinoma. Hum Pathol. 1993; 24:347-354.
   
2. Sherman ME and Mark EJ.
   Effusion cytology in the diagnosis of malignant epithelioid and biphasic pleural mesothelioma. Arch Pathol Lab Med. 1990;114:845-851.