Histiocytic and dendritic cell neoplasms of the mediastinum

Our plain-English summary of Histiocytic and dendritic cell neoplasms of the mediastinum, by E. Baraban, K. Cooper (Mediastinum, 2020).

The study

• Authors: E. Baraban, K. Cooper
• Journal: Mediastinum
• Published: 2020;4:12
• Type of article: Review
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

In this review, we discuss a logical approach to diagnosis of histiocytic and dendritic cell lesions of the mediastinum. We break down the differential diagnosis between true neoplasms of histiocytic and dendritic cells [Rosai-Dorfman disease (RDD), Langerhans cell histiocytosis (LCH), and follicular dendritic cell sarcoma (FDCS)] versus selected neoplasms of other lineages which frequently attract non-neoplastic histiocytes or resemble them morphologically (carcinoma, melanoma, sarcoma, germinoma, mesothelioma, and lymphoma). As neoplasms in the latter category are more common, they should be stringently excluded before diagnosing a lesion in the first group, particularly given enormous differences in clinical management. We also consider histiocytic sarcoma (HS), an extremely rare lesion which, in some cases is likely of intrinsic histiocytic differentiation, whereas in others represents clonal evolution from an underlying non-histiocytic neoplasm.

2020 Mediastinum. All rights reserved.

In plain English

This article was a review, not a study of patients or of asbestos exposure. The authors described how to diagnose histiocytic and dendritic cell lesions of the mediastinum, the central chest area between the lungs. They divided these lesions into two groups. In the first, histiocytic or dendritic cells are themselves the tumor cells, as in Rosai-Dorfman disease, Langerhans cell histiocytosis and follicular dendritic cell sarcoma. The second group is other tumor types that attract many harmless histiocytes or whose cells resemble them, including lymphomas, carcinoma, sarcoma, mesothelioma and germ cell tumors. They also discussed histiocytic sarcoma, an extremely rare tumor. Mesothelioma appeared only as a look-alike. The authors described a lymphohistiocytoid variant whose tumor cells themselves have abundant cytoplasm and deceptively bland nuclei. They wrote that staining tissue for marker proteins (immunohistochemistry) is mandatory whenever mesothelioma is considered. They noted that earlier work had shown BAP1 loss in this variant. The authors concluded that because the look-alike tumors are more common, they must be considered and ruled out before a true histiocytic or dendritic cell neoplasm is diagnosed. The article did not discuss asbestos.

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: narrative review of diagnostic pathology
• Who was studied: No patient group was studied. The review covered histiocytic and dendritic cell lesions of the mediastinum and the tumors that mimic them. Example cases illustrated the figures.
• Main results:
  • The authors' second group was tumors of non-histiocytic lineage, including mesothelioma, that can be mistaken for histiocytic or dendritic cell lesions.
  • The authors stated that true histiocytic and dendritic cell lesions are rare compared with the cancers that can look like them.
  • The lymphohistiocytoid variant of mesothelioma does not attract benign histiocytes. Instead, the authors described the tumor cells themselves as having abundant eosinophilic cytoplasm and deceptively bland nuclei.
  • The authors wrote that immunohistochemistry is mandatory whenever mesothelioma is considered. This means showing several mesothelial markers (calretinin, WT1, D240, CK5/6) and the absence of carcinoma markers (MOC31, BerEP4, CEA).
  • Citing earlier work, the authors noted that BAP1 loss can serve as a marker of malignancy in mesothelial proliferations. They added that this loss had been shown in the lymphohistiocytoid variant.
  • The authors described histiocytic sarcoma as a mixed category. Some cases appear to arise on their own, while others seem to develop from an underlying non-histiocytic neoplasm.
  • The authors wrote that germinoma should be considered for a histiocyte-rich mediastinal lesion in an adult male patient, because these tumors are highly sensitive to radiation and/or chemotherapy.
• The authors' conclusion: The authors concluded that the look-alike tumors of other lineages must be systematically considered and excluded before a true histiocytic or dendritic cell neoplasm is diagnosed.

Topics

Medical terms in this study, explained in our Lexicon: Neoplasm, Mediastinum, Differential Diagnosis, Sarcoma, Carcinoma, Mesothelioma.

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