Am J Surg Pathol. 2014 Mar 10. [Epub ahead of print]

Well-differentiated Papillary Mesothelioma With Invasive Foci.

Churg A1, Allen T, Borczuk AC, Cagle PT, Galateau-Sallé F, Hwang H, Murer B, Murty VV, Ordonez N, Tazelaar HD, Wick M.

Author information

• 1*Department of Pathology, Vancouver General Hospital, Vancouver, BC, Canada †Department of Pathology, The University of Texas Medical Branch Galveston §Department of Pathology and Genomic Medicine, Houston Methodist Hospital **Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX ‡Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY ¶PhenoPath Laboratories, Seattle, WA ††Department of Laboratory Medicine and Pathology, Mayo Clinic in Arizona, Scottsdale, AZ ‡‡Department of Pathology, University of Virginia Health System, Charlottesville, VA ∥Department of Pathology, CHU Caen, Caen, France #Department of Clinical Pathology, Ospedale dell'Angelo Venezia, Mestre, Italy.

Abstract

Well-differentiated papillary mesotheliomas (WDPMs) are usually encountered as incidental findings in the peritoneal cavity in women. Most WDPMs are benign, and the histologic features that indicate a more aggressive course are controversial. We report 20 cases of WDPM, which contained invasive foci. Thirteen cases arose in the peritoneal cavity, 1 in a hernia sac, 3 in the pleural cavity, and 3 in hydroceles. The female:male ratio was 16:4, and age range was 7 to 74 years. Tumor was multifocal in 15 cases. Some tumors showed back-to-back papillae, a pattern mimicking invasion but discernible on pan-keratin stain as compressive crowding. True invasive patterns ranged from simple bland-appearing glands invading the stalks of the papillae to solid foci of invasive tumor of higher cytologic grade than the original WDPM. All 5 tested cases were negative for p16 deletion by fluorescence in situ hybridization, but 2/3 had abnormal karyotypes. Recurrences were seen in 8 patients, and in 4 multiple recurrences were documented. Of 16 patients with follow-up, 14 are alive from periods of 6 months to 6 years (average 3.5 y), and 2 have known recurrent disease. One patient died of disseminated tumor at 8 years but without histologic confirmation of the nature of the tumor. We conclude that WDPM with invasive foci in the papillae appear to be prone to multifocality and recurrence, but that they rarely give rise to life-threatening disease. We suggest that these lesions be called WDPM with invasive foci to alert clinicians to the possibility of recurrence.