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Peritoneal malignant mesothelioma (PMM), and primary peritoneal serous carcinoma (PPSC) and reactive mesothelial hyperplasia (RMH) of the peritoneum. Immunohistochemical and fluorescence in situ hybridisation (FISH) analyses
  1. Toshiaki Kawai1,
  2. Susumu Tominaga1,
  3. Sadayuki Hiroi1,
  4. Sho Ogata1,
  5. Kuniaki Nakanishi1,
  6. Kunimitsu Kawahara2,
  7. Hiroshi Sonobe3,
  8. Kenzo Hiroshima4
  1. 1Department of Pathology and Laboratory Medicine, National Defense Medical College, Tokorozawa, Japan
  2. 2Department of Pathology, Osaka Prefectural Medical Center for Respiratory and Allergic Diseases, Habikino, Japan
  3. 3Department of Laboratoy Medicine, Chugoku Central Hospital, Fukuyama, Japan
  4. 4Department of Pathology, Tokyo Women's Medical University Yachiyo Medical Center, Yachiyo, Japan
  1. Correspondence to Dr Toshiaki Kawai, Toda Central Medical Laboratory, 1-20-7 Honcho, Toda, Saitama 335-0023, Japan; t_kawai{at}


Aims Peritoneal malignant mesothelioma (PMM) is an uncommon tumour, accounting for only 7–9% of all mesotheliomas in Japan. Differential diagnosis between PMM and primary peritoneal serous carcinoma (PPSC), a high-grade serous carcinoma, may be difficult, and separating reactive mesothelial hyperplasia (RMH) from PMM can be even more challenging.

Methods To help differentiate PMM from PPSC and RMH, we used immunohistochemistry to examine mesothelial-associated markers (calretinin, AE1/AE3, CK5/6, CAM5.2, D2-40, WT-1, HBME1, thrombomodulin), adenocarcinoma-associated markers (CEA, BerEP4, MOC31, ER (estrogen receptor), PgR, TTF-1, Claudin-4, Pax8), and malignant-related and benign-related markers (epithelial membrane antigen (EMA), desmin, GLUT-1, CD146 and IMP3), and FISH to examine for homozygous deletion of 9p21. We used formalin-fixed, paraffin-embedded blocks from 22 PMMs (M:F=18:4; subtypes: 16 epithelioid, 6 biphasic), 11 PPSCs and 23 RMHs.

Results Seventeen of the mesotheliomas (four PMM from women) were classified as diffuse, while five were localised. Calretinin was 91% positive in PMM, but negative in PPSC (specificity, 100%). BerEP4, Claudin-4 and PAX8 were all 100% positive in PPSC (specificities, 100%, 95% and 95%, respectively, for excluding PMM). For distinguishing PMM and RMH, sensitivity for EMA in mesothelioma was 68%, while for IMP3 and GLUT-1 it was 64% and 50%, respectively, all with high specificities. FISH analysis revealed homozygous deletion of the 9p21 locus in 11/13 PMMs, but in 0/11 RMHs.

Conclusions Calretinin and BerEP4 may be the best positive markers for differentiating PMM from PPSC. EMA, in combination with IMP3 and desmin, is useful, and homozygous deletion of 9p21 may be helpful, for differentiating PMM from RMH.

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