Background: pleural mesothelioma is a rare cancer in the general population, but it is more common in subjects occupationally exposed to asbestos. Studies with asbestos fiber quantification in pleural tissue are scarce: for this reason, we aimed at undertaking a scoping review to summarize the evidence provided by studies in which asbestos fibers were determined by electron microscopy (SEM or TEM) in human pleural tissues, whether normal or pathologic. Materials and methods: A scoping review of articles that quantified asbestos fibers in human pleural tissue (normal or pathologic) by electron microscopy (SEM or TEM), in subjects with asbestos exposure (if any) was performed. Results: The 12 studies selected comprised 137 cases, out of which 142 samples were analyzed. Asbestos fibers were detected in 111 samples (78%) and were below the detectable limit in 31 samples (22%). The concentration of asbestos fibers detected in the positive samples was distributed from as low as 0.01 mfgdt (millions of fibers per gram of dry tissue) up to 240 mfgdt. However, the minimum concentration of fibers overlaps in the three types of tissues (normal pleura, pleural plaque, mesothelioma) in terms of magnitude; therefore, it is not possible to distinguish a definite pattern which differentiates one tissue from the other. Conclusions: The studies included were heterogeneous as to the representativeness of the samples and analytical techniques; the possibility of false negatives must be considered. It would be desirable to systematically search for asbestos fibers to fill the knowledge gap about the presence of asbestos fibers in normal or pathological pleural tissue in order to better understand the development of the different pleural diseases induced by this mineral.

Peritoneal tissue is the second most affected site by malignant mesothelioma linked to asbestos exposure. This scoping review aims to summarize the findings of the studies in which asbestos fibers in the peritoneum were quantified by electron microscopy, occasionally associated with spectroscopy, both in neoplastic and non-neoplastic tissue. The 9 studies selected comprised 62 cases, out of whom 100 samples were analyzed. Asbestos fibers were detected in 58 samples (58%). In addition, 28 cases had diagnosis of peritoneal mesothelioma. For 32 cases, a lung tumor sample was available: 28/32 samples analyzed presented asbestos fibers; 18/32 reported amphiboles with a range from not detected to 14.2 million fibers per gram of dry tissue (mfgdt); 18/32 reported chrysotile, with a range of 0 to 90 mfgdt. The studies were heterogeneous for type of samples, analytical technology, and circumstances of exposure to asbestos. To evaluate asbestos fibers in the peritoneum and to better understand the association between asbestos exposure and malignant peritoneal mesothelioma, it is desirable that the search for asbestos fibers becomes a routine process every time peritoneal tissue is accessible.