Diffuse intrapulmonary malignant mesothelioma presenting with miliary pulmonary nodules: A case report

Our plain-English summary of Diffuse intrapulmonary malignant mesothelioma presenting with miliary pulmonary nodules: A case report, by T. Hida, M. Hamasaki, S. Matsumoto, et al (Pathology International, 2015).

The study

• Authors: T. Hida, M. Hamasaki, S. Matsumoto, S. Abe, K. Takakura, K. Hiroshima, K. Nabeshima
• Journal: Pathology International
• Published: 2015;65(6):318-23
• Type of article: Case report
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A 67-year-old male with a history of asbestos exposure presented with fever, cough, and dyspnea and was found to have diffuse granular shadowing in both lungs, right pleural effusion, and hilar and mediastinal lymphadenopathy upon chest computed tomography. For definitive diagnosis, a thoracoscopic lung biopsy was performed. Intraoperative findings showed no remarkable macroscopic changes in the visceral and parietal pleura, although a high level of hyaluronic acid in the pleural effusion was noted. Histological findings showed proliferation of atypical cells with round-to-oval nuclei, prominent nucleoli, and eosinophilic cytoplasms. These cells were arranged into sheets or tubules and were located predominantly in the lung parenchyma. Lymphovascular invasion was conspicuous. Immunohistochemically, tumor cells were positive for calretinin, D2-40, and CK5/6, focally positive for Ber-EP4, but negative for WT-1, TTF-1, CEA, and MOC31. Fluorescence in situ hybridization for the tumor suppressor p16 revealed homozygous deletion in the tumor cells. Therefore, we diagnosed the tumor as diffuse intrapulmonary malignant mesothelioma (DIMM). The patient had a poor response to chemotherapy and died 1 year after diagnosis. Although rare, DIMM should be considered when patients present with multiple, tiny intrapulmonary nodules, regardless of macroscopic pleural changes. Furthermore, this is the first report on p16 status in DIMM.

© 2015 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd.

In plain English

This case report described a 67-year-old man exposed to asbestos during 10 years of work as a slate transporter in his twenties. The fiber type for this patient was not stated. He had fever, cough and breathlessness. Chest CT showed tiny nodules throughout both lungs, fluid around the right lung and enlarged chest lymph nodes. During a thoracoscopic lung biopsy the pleura looked unremarkable, but the pleural fluid had a high hyaluronic acid level (686 000 ng/mL). Microscopically, tumor nodules lay within the lung tissue, with marked spread into lymph and blood vessels; no tumor was seen on the pleural surface. Staining results and a p16 gene test (homozygous deletion in 129 of 138 tumor cells) led the authors to diagnose epithelioid diffuse intrapulmonary malignant mesothelioma (DIMM), a variant of malignant pleural mesothelioma. He responded poorly to chemotherapy and died one year after diagnosis. The authors concluded that DIMM should be considered when patients have multiple tiny lung nodules, whether or not the pleura looks abnormal. They noted that the parietal pleura could not be fully examined because no pleurectomy or autopsy was done.

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 67-year-old man with fever, cough and dyspnea, reported by authors at institutions in Japan; dates not stated
• Exposure: Asbestos exposure from 10 years of employment as a slate transporter during his twenties; the fiber type for this patient is not stated (crocidolite appears in the article only for a previously published case in Table 1)
• Main results:
  • Chest CT showed diffuse granular shadowing with a random distribution in both lungs, right pleural effusion, and bilateral hilar and mediastinal lymphadenopathy
  • Hyaluronic acid in the patient's pleural effusion was markedly elevated at 686 000 ng/mL
  • Soluble mesothelin-related peptide, measured after diagnosis, was increased to 6.6 nmol/L (normal less than 1.5 nmol/L)
  • No obvious pleural lesions were seen in the biopsy specimens, and no tumor growth was observed on the pleural surface
  • Marked lymphovascular involvement was found along bronchovascular bundles and interlobular septa
  • Tumor cells were diffusely positive for calretinin, D2-40 and CK5/6, focally positive for Ber-EP4, and negative for WT-1, TTF-1, CK7, CK20, CEA, MOC31 and CD68; the case was diagnosed as epithelioid MPM/DIMM
  • p16 FISH showed homozygous deletion of p16 in 93.5% (129/138) of the patient's tumor cells
  • The article states that not all sections showed evidence of asbestos bodies
  • The patient had a poor response to two courses of cisplatin plus pemetrexed and died 1 year after diagnosis from worsening respiratory failure
• The authors' conclusion: The authors concluded that DIMM is a rare variant of malignant pleural mesothelioma that should be added to the differential diagnosis when a patient has multiple tiny intrapulmonary nodules, regardless of macroscopic pleural lesions
• Limitations the authors state:
  • A full pathologic examination of the parietal pleura could not be done because neither pleurectomy nor autopsy was performed
  • The authors state that more case studies of DIMM are needed before the p16 finding can be taken to suggest common tumor mechanisms in MPM and DIMM

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: Malignant Mesothelioma, Asbestos Exposure, Dyspnea, Pleural Effusion, Lymphadenopathy, Biopsy, Parietal Pleura, Hyaluronic Acid.

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