The existence of an in situ phase of (malignant) mesothelioma was only demonstrated a few years ago (in 2019). As mesotheliomas are predominantly caused by asbestos fibers and can be recognized as occupational disease (OD) No. 4105 in accordance with Appendix 1 of the Occupational Diseases Ordinance (ODO), whereas the legal definition does not explicitly include any precursors, it was controversial whether mesothelioma in situ should be recognized as OD.Here we present the case history of a patient (69 years, male) with histologically confirmed mesothelioma in situ of the left parietal pleura after pleurectomy and proven occupationally insured asbestos exposure.As both mesothelioma in situ and invasive mesothelioma can be triggered by exposure to asbestos fiber dust, sufficient insured occupational exposure was proven for the probability of connection (Latin: "conditio sine qua non") and the clinical picture was only initially diagnosed earlier, recognition as OD No. 4105 ODO was recommended to the social court according to a medical expert report. This recommendation was followed by the social court and finally by recognition by the statutory accident insurance provider.In the authors' (m/f/d) opinion, mesothelioma in situ can already be recognized as OD based on the current version of OD No. 4105 ODO. The high probability of progression into an invasive mesothelioma and the fact that no relevant difference is known between the risk factors of mesothelioma in situ and an invasive mesothelioma of the pleura, pericardium and peritoneum, as well as the fact that regarding other ODs, precursors of malignant diseases have already been included in the legal definition (e.g., OD No. 1301, 1321 and 5103 ODO), justify extending the legal definition of OD to this stage of the disease, at least by analogy. Nevertheless, for clarification, to avoid legal uncertainty and the resulting disputes and in the interest of uniform application of the ODO, it is recommended that the legislator expands the legal definition of OD No. 4105 ODO to include precursors of invasive mesothelioma, here mesothelioma in situ. Furthermore, the ODs listed in the ODO should also be checked in general to see whether the inclusion of precursors of the respective disease in the legal definition is indicated based on new scientific findings.
