Small cell mesothelioma: A rare entity and diagnostic pitfall mimicking small cell lung carcinoma on fine-needle aspiration

Our plain-English summary of Small cell mesothelioma: A rare entity and diagnostic pitfall mimicking small cell lung carcinoma on fine-needle aspiration, by Y. Zhang, A. Afify, R.F. Gandour-Edwards, et al (Diagnostic Cytopathology, 2016).

The study

• Authors: Y. Zhang, A. Afify, R.F. Gandour-Edwards, J.W. Bishop, E.C. Huang
• Journal: Diagnostic Cytopathology
• Published: 2016;44(6):526-9
• Type of article: Case report
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Small cell mesothelioma (SCM) is an extremely rare variant of epithelioid mesothelioma that can be mistaken for other forms of small round blue cell tumors, particularly small cell lung carcinoma (SCLC). Here, we describe a fine-needle aspiration (FNA) from a pleural lesion in a 75-year-old man with a history of known asbestos exposure. The FNA revealed cohesive clusters of uniform small round blue cells with high nuclear-to-cytoplasmic ratio, finely powdery chromatin, small inconspicuous nucleoli, and scant amount of cytoplasm. Mitoses were infrequent and nuclear molding was absent. Immunochemical profile supported a mesothelial origin, which was later confirmed by pleurectomy with a diagnosis of SCM. This report demonstrates the difficulties in cytologic evaluation of lung FNAs in differentiating SCM from SCLC or other small round blue cell tumors. As therapy differs for SCM, early recognition of the cytologic features is essential in making the correct diagnosis needed for appropriate clinical management. Diagn. Cytopathol. 2016;44:526-529. © 2016 Wiley Periodicals, Inc.

© 2016 Wiley Periodicals, Inc.

In plain English

This is a case report of one patient with small cell mesothelioma, a rare form of epithelioid mesothelioma that can be mistaken for small cell lung carcinoma. The patient was a 75-year-old man with a history of prior asbestos exposure. The article does not say which fiber type was involved or how he was exposed. A CT scan showed a 2.5 cm mass on the pleura, fluid around the right lung, and extensive pleural plaques. Cells taken by fine-needle aspiration were small and uniform, with few dividing cells and no nuclear "molding". Stains supported a mesothelial origin, and a diagnosis consistent with malignant mesothelioma was made. Surgery removing the right pleura found a tumor that was 50% small cell, 30% clear cell and 20% classic epithelioid type, with metastasis in one lymph node. After four cycles of chemotherapy, he had no evidence of recurrence or metastasis at 12 months. The authors concluded that the absence of nuclear molding and crush artifact, and fewer dividing cells, help separate this tumor from small cell lung carcinoma.

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 report (single patient)
• Who was studied: One 75-year-old man with prior asbestos exposure who had worsening shortness of breath, seen at the University of California, Davis Medical Center, Sacramento
• Exposure: Prior asbestos exposure. Fiber type, job, products and dose are not reported. Imaging showed extensive pleural plaques.
• Main results:
  • The chest CT scan showed a 2.5 cm pleural-based mass with right pleural effusion and extensive pleural plaques.
  • On fine-needle aspiration, mitoses (dividing cells) were infrequent and nuclear molding and smearing artifacts were absent.
  • Tumor cells stained strongly and diffusely for cytokeratin (AE1 and AE3) and WT-1, and focally and weakly for calretinin.
  • The pleurectomy specimen was 50% small cell, 30% clear cell and 20% classic epithelioid type. The aspiration sample consisted only of the small cell component.
  • In the surgical specimen, mitoses were up to 20 per 10 high power fields.
  • Metastasis was found in one peri-diaphragmatic lymph node. The final pathologic stage was T3N2Mx.
  • The patient received four cycles of chemotherapy with cisplatin and pemetrexed (printed in the article as 'premetrexed').
  • The patient was doing well, with no evidence of recurrence or metastasis after 12 months of surveillance.
• The authors' conclusion: The authors concluded that small cell mesothelioma can be diagnostically challenging in fine-needle aspiration samples. In their view, the absence of nuclear molding, the absence of nuclear crush artifact, and lower mitotic activity are characteristics that help separate it from small cell lung carcinoma, especially when there is not enough material for additional tests.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Carcinoma, Fine-Needle Aspiration, Epithelioid, Asbestos Exposure.

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