Mesothelial tumors
Benign epithelial mesothelioma (benign neoplasm of pleura)

Topic Completed: 1 July 2013

Revised: 1 March 2019

Copyright: 2003-2019,, Inc.

PubMed Search: Benign epithelial mesothelioma pleura
Page views in 2018: 1,119
Page views in 2019 to date: 295
Cite this page: Avadhani V. Benign epithelial mesothelioma (benign neoplasm of pleura). website. Accessed March 19th, 2019.
Definition / general
  • Benign pleural neoplasm with mesothelial differentiation
  • Also called adenomatoid tumor
  • More common at other sites - epididymis, spermatic cord, prostate, ejaculatory duct, uterus, fallopian tube
  • Rarely reported in adrenal gland (suprarenal occurrence of an adenomatoid tumor, J Urol 1988;139:348)
Clinical features
  • Usually incidental mass
Case reports
  • Surgical resection is curative
Gross description
  • Tan-yellow nodule with firm cut surface
Gross images

Images hosted on other servers:

Testis with well encapsulated tumor

Microscopic (histologic) description
  • Irregularly arranged dilated tubules or gland-like spaces lined by plump epithleioid cells in fibrotic stroma
  • May have epithelioid cells in clusters
  • Individual cells may have eccentric nuclei with abundant cytoplasm and vacuolization
  • Lymphoplasmacytic infiltrate may be seen at periphery of the tumor
  • No / rare mitoses (Ki67: 1 - 2%)
Microscopic (histologic) images

Images hosted on other servers:

Genital tract tumors: dilated tubular structures

Cytology description
  • Cells are arranged in sheets, cords, glandular patterns
  • Cells have eccentric vesicular nuclei with fine vesicular chromatin and abundant vacuolated cytoplasm (Acta Cytol 1999;43:495)
Cytology images

Images hosted on other servers:

Monolayered sheets of cells

Adenomatoid tumor of epididymis

Electron microscopy description
  • Branching plasmalemmal microvilli with intercellular adhesion complexes, indicative of mesothelial derivation
Differential diagnosis
Back to top