Primary lesions that may imitate metastatic tumors histologically: A selective review

Our plain-English summary of Primary lesions that may imitate metastatic tumors histologically: A selective review, by M.R. Wick (Seminars in Diagnostic Pathology, 2018).

The study

• Author: M.R. Wick
• Journal: Seminars in Diagnostic Pathology
• Published: 2018;35(2):123-142
• Type of article: Review
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Several primary pathologic entities in diverse anatomic locations have the potential to simulate metastatic neoplasms histologically. Their misinterpretation as such may result in needless and extensive clinical evaluations that are intended to detect a presumed malignancy at another site. More importantly, mistakes of this type can deprive patients of surgical excisions that could be curative. This presentation considers a review of selected primary lesions that can simulate metastases. They include hemangioblastoma, glioblastoma and meningioma with epithelial metaplasia, choroid plexus carcinomas, primary neuroendocrine carcinomas in unusual locations, special forms of sinonasal and salivary glandular adenocarcinoma, clear-cell thyroid carcinomas, unusual microscopic subtypes of pulmonary adenocarcinoma, epithelioid myomelanocytomas ("sugar tumors"), mesotheliomas, primary thymic carcinomas, endodermal choristomas of the interatrial myocardium, peripheral cholangiocarcinoma, adrenocortical carcinoma, adenocarcinomas of the urinary bladder, mucinous and "rhabdoid" tumors of the ovaries, rete testis adenocarcinomas, interdigitating dendritic-cell sarcoma of lymph nodes, selected sweat gland carcinomas, cutaneous Merkel cell carcinoma, primary dermal and subcutaneous melanoma, mucosal and visceral melanomas, epithelioid sarcoma, clear-cell sarcoma, and adamantinoma of long bones. Differential diagnostic observations are emphasized in reference to those lesions.

Copyright © 2017 Elsevier Inc. All rights reserved.

In plain English

This article is a selective narrative review by a single pathologist, not a study of patients. It surveyed published work on primary tumors in many organs, from the brain to bone, that can look under the microscope like cancer spread from elsewhere (metastases). The author stated that mistaking a primary tumor for a metastasis can lead to needless searches for another cancer and can deprive patients of surgery that could be curative. The article does not discuss asbestos. One short section covered pleural mesothelioma. It said several forms of epithelioid pleural mesothelioma can imitate metastatic carcinoma, and sarcomatoid mesothelioma can resemble sarcomatoid carcinomas, sarcomatoid melanomas and sarcomas. The author wrote that, in the author's experience, sarcomatoid mesotheliomas express keratin in virtually every case. The review described older staining methods for telling epithelioid mesothelioma from adenocarcinoma. It summarized antibody panels recommended by other researchers, such as calretinin, cytokeratin 5/6, CEA and MOC-31 (Ordonez). It also described a heart lesion once called "mesothelioma of the AV node" that, according to the studies it cited, does not have the features of mesothelial cells.

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: Selective narrative review of published literature, with the author's own diagnostic experience; no new patient data
• Who was studied: No study population; the review covers selected primary tumors of the nervous system, head and neck, thyroid, lung and pleura, thymus, heart, liver, adrenal, bladder, gonads, lymph nodes, skin, soft tissue and bone, as described in published literature
• Main results:
  • The review states that several forms of epithelioid malignant mesothelioma of the pleura can imitate metastatic carcinoma under the microscope, including the ordinary type and clear-cell, rhabdoid and small-cell variants
  • The review states that sarcomatoid (spindle-cell) mesothelioma can resemble metastatic sarcomatoid carcinomas, sarcomatoid melanomas and sarcomas
  • The author disagreed with the suggestion that keratin-negative sarcoma-like pleural tumors should all be called mesothelioma, writing that in the author's experience sarcomatoid mesotheliomas express keratin in virtually every case
  • The review states that, historically, epithelioid mesothelioma was separated from metastatic adenocarcinoma by histochemical stains, because adenocarcinomas make epithelial mucin and mesotheliomas do not. It adds that these stains are much less helpful when the question is sarcomatoid mesothelioma versus spindle cell carcinoma or sarcoma
  • The review quoted a recommendation by Ordonez (another researcher) for a four-marker panel to diagnose epithelioid mesothelioma: two positive markers (calretinin and cytokeratin 5/6, or WT1 or podoplanin) and two negative markers (CEA and MOC-31, or B72.3, Ber-EP4 or BG-8)
  • The review reported that Yaziji and coworkers, analyzing 12 markers, concluded that a 3-marker panel (calretinin, MOC31 and BG8) was sufficient and accurate for separating adenocarcinoma from epithelioid mesothelioma
  • The review states that a heart lesion near the atrioventricular node, formerly called "mesothelioma of the AV node", has been shown by immunohistochemical studies not to have the features of mesothelial cells. The author proposed calling it an intracardiac endodermal choristoma
• The authors' conclusion: The author stated that mistaking a primary tumor for a metastasis can lead to needless clinical evaluations and, more importantly, can deprive patients of surgical removal that could be curative. The review emphasized points that help tell these tumors apart from metastases.

Topics

Medical terms in this study, explained in our Lexicon: Neoplasm, Carcinoma, Adenocarcinoma, Epithelioid, Mesothelioma, Rhabdoid, Rete Testis, Sarcoma.

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