Mesotheliomas with crystalloid structures: report of nine cases, including one with oncocytic features

Our plain-English summary of Mesotheliomas with crystalloid structures: report of nine cases, including one with oncocytic features, by N.G. Ordóñez (Modern Pathology, 2012).

The study

• Author: N.G. Ordóñez
• Journal: Modern Pathology
• Published: 2012;25(2):272-81
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Although the presence of crystalloids has historically been of largely academic interest or simply an intriguing curiosity, these structures have occasionally been useful in the differential diagnosis of some tumors. Crystalloids have only rarely been reported in mesotheliomas, and their presence in these tumors has not been sufficiently investigated, nor has their potential value as an ultrastructural marker for mesothelioma been established. The finding of a case of mesothelioma in which the vast majority of the neoplastic cells contained intracytoplasmic crystalloids prompted a search for these structures in 69 consecutive cases of mesothelioma (59 epithelioid, 7 sarcomatoid, 3 mixed-epithelioid sarcomatoid). Crystalloids were found in 9 (15%) of the 59 epithelioid mesotheliomas, indicating that these structures are not as rare as had been thought. That these inclusions were demonstrated in tumors exhibiting diverse histological patterns and were not confined to a single subtype of epithelioid mesothelioma indicates that, because of their unique morphology, when present, they can assist in the diagnosis of these tumors. In addition, oncocytic features were also seen in one of the cases with crystalloid inclusions. Pathologists should be aware of the fact that, even though uncommon, mesotheliomas can present oncocytic morphology and, therefore, these tumors should be included in the differential diagnosis of those neoplasms that display similar morphological features, and which can metastasize to the serosal membranes. To my knowledge, an oncocytic mesothelioma has not previously been reported.

In plain English

This article described crystalloids, tiny crystal-like structures seen by electron microscopy inside and around mesothelioma cells. After finding one tumor in which most cells contained them, the author searched 69 consecutive mesotheliomas (59 epithelioid, 7 sarcomatoid, 3 mixed epithelioid and sarcomatoid). Crystalloids were found in 9 (15%) of the 59 epithelioid tumors and in none of the seven sarcomatoid tumors. The nine patients (seven men and two women, aged 53 to 74) all had tumors arising in the pleura. Six had a history of asbestos exposure and five a history of smoking. Seven died of the disease 5 to 55 months after diagnosis, one was alive without evidence of disease at 60 months, and one had no follow-up. All nine tumors stained for calretinin and podoplanin. One tumor (case 5) had oncocytic features: its cells were packed with mitochondria. The author concluded that these crystalloids are not rare in mesotheliomas and can serve as a marker of the disease. The author also reported that, to the author's knowledge, no oncocytic mesothelioma had been reported before. The author noted that seven sarcomatoid tumors were too few to rule out crystalloids in that type.

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: a light microscopic, immunohistochemical and electron microscopic (ultrastructural) study of consecutive mesothelioma cases
• Who was studied: 69 consecutive mesotheliomas (59 epithelioid, 7 sarcomatoid, 3 mixed epithelioid and sarcomatoid). The nine cases with crystalloids came from seven male and two female patients aged 53 to 74 years (mean 61), all with pleural tumors. Dates of the cases are not given.
• Exposure: Asbestos exposure was not the subject of the study. A history of asbestos exposure was recorded in six of the nine patients with crystalloids, and a history of smoking in five. No fiber types, jobs or doses are given.
• Main results:
  • Crystalloids were found in 9 (15%) of the 59 epithelioid mesotheliomas.
  • No crystalloids were found in any of the seven sarcomatoid mesotheliomas. All nine cases with crystalloids were epithelioid.
  • Among the nine patients with crystalloids, all tumors originated in the pleura.
  • Among the nine patients, seven died of disease 5 to 55 months (mean 17 months) after diagnosis. One was alive with no evidence of disease at 60 months, and one had no follow-up information.
  • All nine tumors showed diffuse, strong staining for calretinin and podoplanin.
  • Keratin 5/6 staining was positive in seven of seven cases tested, and WT-1 in six of eight cases tested.
  • None of the nine tumors stained for CEA, TAG-72 (B72.3), MOC-31 or CD15.
  • None of the nine tumors were mucicarmine-positive.
  • The most common crystalloid type inside cells was rigid, hollow tubules with a honeycomb structure, seen in six cases. Tubular crystalloids outside cells were found in four cases.
  • In one case (case 5), the tumor was made of polygonal cells with dense eosinophilic cytoplasm showing oncocytoid features. Electron microscopy showed this was due to a large number of mitochondria.
• The authors' conclusion: The author concluded that the crystalloid inclusions are not rare in mesotheliomas and, when present, can serve as an ultrastructural marker of mesothelioma. The author also stated that, to the author's knowledge, an oncocytic mesothelioma had not previously been reported.
• Limitations the authors state:
  • The number of sarcomatoid mesotheliomas examined (seven) was too small to conclude that crystalloids do not occur in that tumor type.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Differential Diagnosis, Epithelioid, Sarcomatoid, Neoplasm, Metastasis.

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