The characteristic appearance of mesothelial cells on electron microscopy (ie, numerous long, slender, and smooth microvilli) point to the diagnosis of mesothelioma.1,3,29 By definition, LMMs are immunohistochemically, and ultrastructurally identical to DMMs. Epithelium-type LMMs predominate, and very few tumors are purely sarcomatous. DMMs show macroscopic and/or microscopic evidence of widespread tumors on the serosal surface, whereas LMMs are well circumscribed. Reported cases34–37 of LMM that recur as DMM should be carefully reviewed to ensure that a DMM was not present at the time of the original diagnosis. In conclusion, we would suggest that, although LMMs share similar microscopic and immunohistochemical features with DMMs, LMM should probably be considered a separate entity, distinct by its occult clinical presentation, its sharp morphologic demarcation, and its higher curability with surgical resection.