Lymphohistiocytoid mesothelioma. An often misdiagnosed variant of sarcomatoid malignant mesothelioma

Our plain-English summary of Lymphohistiocytoid mesothelioma. An often misdiagnosed variant of sarcomatoid malignant mesothelioma, by H.S. Khalidi, L.J. Medeiros, H. Battifora (American Journal of Clinical Pathology, 2000).

The study

• Authors: H.S. Khalidi, L.J. Medeiros, H. Battifora
• Journal: American Journal of Clinical Pathology
• Published: 2000;113(5):649-54
• Type of article: Case report
• Cited by: 32 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Three cases of lympho-histiocytoid mesothelioma, a rare variant of pleural sarcomatoid malignant mesothelioma, are described. Histologically, the neoplasms were characterized by a diffuse discohesive proliferation of atypical histiocytoid cells intermixed with a marked lymphocytic and lesser plasmacytic infiltrate. One case initially was misdiagnosed as a ganglioneuroma, a second case was misinterpreted as malignant lymphoma, and a third case was sent in consultation with the differential diagnosis of inflammatory pseudotumor vs mesothelioma. Immunohistochemical studies showed strong and generalized expression of cytokeratins and vimentin by the neoplastic histiocytoid cells in all 3 cases. Two cases were positive for calretinin, one of which also was positive for HBME-1, thrombomodulin, and LeuM1. None of the cases stained with the epithelial glycoprotein markers carcinoembryonic antigen, B72.3, and Ber-EP4, or the blood group antigen, BG-8. The immunophenotype of the lymphoplasmacytic infiltrate revealed predominantly reactive, mature T cells, with fewer polytypic plasma cells, histiocytes, and B cells. In lymphohistiocytoid mesothelioma, as in the usual examples of sarcomatoid mesothelioma, the demonstration of cytokeratin expression by the neoplastic cells is the most useful diagnostic finding that allows exclusion of other neoplasms with which this entity may be confused.

In plain English

This article described three patients with lymphohistiocytoid mesothelioma, a rare form of sarcomatoid malignant mesothelioma of the pleura, the lining of the chest. The cases came from 612 malignant mesotheliomas in one author's consultation files. The patients were men aged 60 and 67 and a woman aged 74. No history of asbestos exposure could be established. For one patient it was unknown. One man's CT scan showed bilateral pleural plaques and calcifications, which the article called typical of asbestosis. Each tumor was hard to diagnose: one was first called a ganglioneuroma, one a lymphoma, and one possibly a reactive process. The tumor cells were mixed with many inflammatory cells, mostly mature T lymphocytes. In all three cases the tumor cells stained for cytokeratin, a protein marker. All three patients were alive after 6 years, 10 months and 3 months. The authors concluded that cytokeratin staining is the most useful finding for ruling out tumors this one can be mistaken for. They cautioned that sarcomatoid lung carcinoma and thymic tumors also stain for cytokeratin. Follow-up was too short to judge two patients' outcomes.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case series (3 cases from a pathology consultation file)
• Who was studied: 3 patients with pleural lymphohistiocytoid mesothelioma (2 men aged 60 and 67, 1 woman aged 74), selected from 612 malignant mesotheliomas in the consultation files of one author
• Exposure: No history of asbestos exposure could be established. The asbestos history was recorded as negative in cases 1 and 3 and unknown in case 2.
• Main results:
  • In case 3, CT showed bilateral pleural plaques and calcifications, described as typical of asbestosis, although that patient's asbestos history was recorded as negative.
  • Case 1 was originally diagnosed as a ganglioneuroma.
  • Case 3 was initially diagnosed as non-Hodgkin lymphoma, according to the text and Table 2.
  • In case 2, the referring pathologist considered reactive mesothelial hyperplasia or malignant mesothelioma.
  • In all 3 cases, the tumor cells were diffusely positive for cytokeratin.
  • Vimentin was positive in 2 of 3 tumors (cases 2 and 3).
  • Calretinin was positive in 2 of 3 tumors (cases 1 and 3).
  • All 3 tumors were negative for carcinoembryonic antigen, B72.3, Ber-EP4 and BG-8.
  • Most of the accompanying reactive lymphocytes were mature T cells.
  • All 3 patients were alive at follow-up: after 6 years (case 1), 10 months (case 2) and 3 months (case 3).
  • Case 1 recurred after 5 years, which the authors took to indicate indolent behavior.
  • The 3 cases were almost 0.5% of the authors' malignant mesothelioma series, and approached 3% of the 107 sarcomatoid cases.
• The authors' conclusion: The authors concluded that showing cytokeratin expression by the tumor cells is the most useful diagnostic finding for excluding other tumors that this one may be confused with.
• Limitations the authors state:
  • Follow-up was too short to reliably assess clinical behavior in cases 2 and 3.
  • Cytokeratin staining does not distinguish this tumor from sarcomatoid carcinoma of the lung involving the pleura, because both express cytokeratin.
  • Thymomas and thymic carcinomas also express cytokeratin, which may cause diagnostic difficulty with this tumor.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Lymphohistiocytoid, Mesothelioma, Sarcomatoid, Malignant Mesothelioma, Neoplasm, Differential Diagnosis, Calretinin, HBME-1.

Related studies

• Lymphohistiocytoid mesothelioma: a rare lymphomatoid variant of predominantly sarcomatoid mesothelioma — D.W. Henderson, H.D. Attwood, et al. (1988)
• Immunohistochemical analysis still has a limited role in the diagnosis of malignant mesothelioma. A study of thirteen antibodies — F. Roberts, C.M. Harper, et al. (2001)
• Value of mesothelial and epithelial antibodies in distinguishing diffuse peritoneal mesothelioma in females from serous papillary carcinoma of the ovary and peritoneum — R.L. Attanoos, R. Webb, et al. (2002)
• Immunohistochemical panels for differentiating epithelial malignant mesothelioma from lung adenocarcinoma: a study with logistic regression analysis — R. Carella, G. Deleonardi, et al. (2001)
• Expression of calretinin, thrombomodulin, keratin 5, and mesothelin in lung carcinomas of different types: an immunohistochemical analysis of 596 tumors in comparison with epithelioid mesotheliomas of the pleura — M. Miettinen, M. Sarlomo-Rikala (2003)
• Calretinin, thrombomodulin, CEA, and CD15: a useful combination of immunohistochemical markers for differentiating pleural epithelial mesothelioma from peripheral pulmonary adenocarcinoma — C.E. Comin, L. Novelli, et al. (2001)

Browse more research in American Journal of Clinical Pathology, or return to medical research.