Well-differentiated papillary mesothelioma

Epidemiology

This is an unusual variant of mesothelioma of low malignant potential. It occurs in the peritoneum predominantly in young women (3^rd and 4^th decade)¹, and in the pleura, in middle aged to elderly patients⁴, equally between sexes or predominantly in men¹. Rarely, it occurs in the pericardium² or tunica vaginalis³. There is some reported association in pleural cases with asbestos exposure⁴, but less well established than for diffuse malignant mesothelioma.

Clinical features

There is often a free-flowing effusion. Patients may present with recurrent pneumothoraces⁴.

Radiology

Pleural cases commonly show effusions. There may be calcified pleural plaques. Peritoneal cases are associated with ascites and bowel wall / mesenteric thickening.

Macroscopic appearances

There may be studding of the mesothelial surface by small white to tan nodules or fine granularity, or a single fungating mass.

Histopathology

There is a papillary architecture, consisting of fibrovascular cores covered by cuboidal mesothelial cells with minimal cytological atypia. The papillae may form multiple small clusters up to i cm in diameter⁴. Focal invasion of the stroma may occur but is limited, not extending into subpleural alveoli or adipose tissue⁴. The cytology is bland. Cells may contain subnuclear vacuoles. Mitoses are not seen. Psammoma bodies may be seen.

Immunohistochemistry

The limited evidence is that the pattern of Immunoreactivity is as for diffuse epithelioid malignant mesothelioma.

Differential diagnosis

• Reactive mesothelial hyperplasia: usually also shows inflammation. A papillary configuration is unusual but when present, the cores may be hyalinised⁴. Staining for desmin may be helpful.

• Diffuse malignant mesothelioma with a prominent papillary pattern: exclusion requires adequate sampling. The papillae show a back-to-back arrangement, lacking stout fibrovascular cores.

• Carcinomatosis of the peritoneum or pleura: immunohistochemistry will resolve this differential.

Management

Prognosis

Generally, this is an indolent condition, but prognosis is variable, with with some cases resolving on chemotherapy, others progressing to diffuse malignant mesothelioma¹. In one study, average survival was 74 months⁴ (compared with less than one year for diffuse malignant mesothelioma).

References

¹Butnor, K. J., T. A. Sporn, et al. (2001). "Well-differentiated papillary mesothelioma." Am J Surg Pathol 25(10): 1304-9.

²Sane, A. C. and V. L. Roggli (1995). "Curative resection of a well-differentiated papillary mesothelioma of the pericardium." Arch Pathol Lab Med 119(3): 266-7.

³Jones, M. A., R. H. Young, et al. (1995). "Malignant mesothelioma of the tunica vaginalis. A clinicopathologic analysis of 11 cases with review of the literature." Am J Surg Pathol 19(7): 815-25.

⁴Galateau-Salle, F., J. M. Vignaud, et al. (2004). "Well-differentiated papillary mesothelioma of the pleura: a series of 24 cases." Am J Surg Pathol 28(4): 534-40.

This page last revised 24.12.2003.