The pathology associated with therapeutic procedures in malignant mesothelioma

Our plain-English summary of The pathology associated with therapeutic procedures in malignant mesothelioma, by R.L. Attanoos, A.R. Gibbs (Histopathology, 2004).

The study

• Authors: R.L. Attanoos, A.R. Gibbs
• Journal: Histopathology
• Published: 2004;45(4):393-7
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Aims: To describe iatrogenic pathological lesions in malignant pleural mesothelioma.

Methods And Results: All cases of malignant pleural mesothelioma confirmed by antemortem pleural biopsy and undergoing post mortem examination over a 7-year period (1995-2001) formed the study group. This comprised 48 malignant pleural mesotheliomas [epithelioid (n = 21), biphasic (n = 14) and sarcomatoid (n = 13)]. Twenty-eight of 48 (58%) had received chemical (talc) pleurodesis, 30/48 (63%) palliative localized radiotherapy, 6/48 (13%) chemotherapy, and 14/48 (30%) surgery [12/48 (26%) pleural decortication and 2/48 (4%) pleuropneumonectomy].

Conclusions: Talc pleurodesis induces a marked pseudosarcomatous fibroblastic proliferation which may impart a biphasic pattern to the neoplasm. In more chronic cases, paucicellular fibrosis with a foreign body giant cell reaction is noted. The talc is polarizable and deposited in linear fashion within the tumour. In 2/28 (7%) pleurodesis cases platyform ferruginous bodies were seen in the peripheral alveolated lung parenchyma and these mimicked asbestos bodies. An awareness of this is important to prevent false attribution to asbestos. Talc could be identified by transmission electron microscopic mineral analysis in 5/15 (33%) cases examined. Tumour nodules developing subjacent to iatrogenic wound sites were noted in 8/48 (17%) cases. In 6/8 (75%) of these cases, comparative assessment of the locally irradiated subcutaneous chest wall tumour, with background pleural mesothelioma, showed no morphological difference in architectural tumour growth pattern, extent of necrosis, cytological or nuclear pleomorphism, mitotic activity or tumour immunophenotype. In 2/8 (25%) cases the locally irradiated tumour showed prominent bizarre multinucleated tumour giant cells and intense mixed inflammation, a feature not seen in the background (non-irradiated) tumour. All six malignant pleural mesotheliomas receiving chemotherapy appeared refractory to treatment in that chemotherapy did not appear to have any significant effect on the tumour morphology, cytonuclear pleomorphism, mitotic activity, extent of necrosis or immunophenotype. In the 12 decortication specimens and two pleuropneumonectomy resections, post mortem examination identified evidence of residual malignant mesothelioma of similar morphological subtype and immunophenotype to the resected tumour.

In plain English

This study from Llandough Hospital in Cardiff, UK, looked at 48 people with malignant pleural mesothelioma (cancer of the lining around the lungs) who had been diagnosed by biopsy during life and examined after death between 1995 and 2001. The authors compared biopsy and post mortem tissue to describe what the tumours looked like under the microscope after various treatments. Twenty-eight had talc pleurodesis, in which talc is put into the chest lining to stop fluid building up. In 10 of these, talc-related changes were seen after death. In 7 of the 10 there was a dense growth of spindle-shaped scar-forming cells around talc crystals, which the authors said may make the tumour look biphasic. In 2 of the 28, iron-coated bodies in the lung mimicked asbestos bodies. Mineral analysis found talc in 5 of 15 cases tested. Tumour nodules grew under biopsy wound sites in 8 of 48. Two of these 8 locally irradiated nodules showed bizarre giant cells. Chemotherapy and surgery did not appear to change the tumour's appearance. The authors concluded that awareness of these effects is needed to prevent misdiagnosis, including wrongly attributing a mesothelioma to 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: Retrospective descriptive series of post mortem cases (pathology study comparing biopsy and post mortem tissue after treatment)
• Who was studied: 48 malignant pleural mesotheliomas confirmed by biopsy during life and examined at post mortem, Llandough Hospital, Cardiff, UK, 1995 to 2001. Subtypes at post mortem were 21 epithelioid, 14 biphasic and 13 sarcomatoid.
• Exposure: Therapeutic procedures, not asbestos exposure. Of the 48 cases, 28 had chemical (talc) pleurodesis, 30 had palliative localized radiotherapy, 6 had chemotherapy, 12 had pleural decortication and 2 had pleuropneumonectomy. The patients' asbestos exposure is not reported.
• Main results:
  • Among the 10 talc pleurodesis cases with corresponding findings at post mortem, 7 of 10 showed a florid fibroblastic spindle cell proliferation around talc crystals. No mitotic activity or necrosis was seen in the spindle cells.
  • In 3 of the 10 talc cases there was a paucicellular foreign body reaction to talc, without a cellular fibroblastic reaction or inflammation.
  • In 2 of the 28 pleurodesis cases, platyform ferruginous bodies (formed on talc cores) were seen in the outer lung tissue and mimicked asbestos bodies.
  • Transmission electron microscopic mineral analysis detected talc in the lung tissue of 5 of the 15 cases analysed.
  • Tumour nodules developed beneath biopsy wound sites in 8 of 48 cases. In 6 of these 8, the locally irradiated tumour looked no different from the main pleural tumour. In 2 of 8, it showed bizarre multinucleated tumour giant cells and intense mixed inflammation, which were not seen in the non-irradiated tumour.
  • In the 6 chemotherapy cases, chemotherapy did not appear to have any significant effect on tumour appearance, mitotic activity, necrosis or immunophenotype.
  • Prior surgery (12 decortications, 2 pleuropneumonectomies) did not influence tumour morphology. Residual mesothelioma of similar subtype and immunophenotype was found at post mortem.
• The authors' conclusion: The authors concluded that talc pleurodesis can produce a pseudosarcomatous lesion that makes the mesothelioma look biphasic, and can produce ferruginous bodies that mimic asbestos bodies. They concluded that awareness of this is needed to prevent misattributing the mesothelioma to asbestos. They described mesothelioma as largely resistant to radiotherapy and chemotherapy, and said awareness of treatment-induced changes is needed to prevent misdiagnosis.
• Limitations the authors state:
  • The authors noted that, because mesothelioma looks so varied under the microscope, it is difficult to say definitively that a given change was caused only by treatment.

Topics

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

Medical terms in this study, explained in our Lexicon: Pathology, Malignant Mesothelioma, Pleural Mesothelioma, Pleural Biopsy, Epithelioid, Biphasic Mesothelioma, Sarcomatoid, Talc.

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