Clinical history: 76 year old man developed a left sided pleural effusion.
What is your diagnosis?
Discussion and answer
This is a highly cellular specimen of very atypical cells occurring singly, in loose associations and in aggregates. Highly atypical nuclear features include pleomorphism, irregular chromatin clumping, prominent nucleoli, irregular nuclear contours and multinucleation. These atypical cells have variable amounts of dense cytoplasm.
A reasonable differential includes plasmacytoma, malignant melanoma and mesothelioma.
Patient was recently diagnosed via FNAB of paraspinal muscle with malignant mesothelioma (supported by immunohistochemistry). Comparison of this specimen with the previous specimen demonstrated similar appearing malignant cells and this case was signed out as malignant mesothelioma.