Aims: Mesothelioma is a malignant neoplasm of the serosal membranes originating from mesothelial cells. Peritoneal mesothelioma is the second most common mesothelial neoplasm after pleural mesothelioma, accounting for approximately 6%–15% of cases. Due to its high morphological variability, often mimicking other lesions, mesothelioma remains a diagnostic challenge. CDKN2A homozygous deletion has been established as a highly accurate biomarker for differentiating mesothelioma from benign mesothelial proliferations. MTAP immunohistochemistry (IHC) has been proposed as a cheaper and more reproducible surrogate for CDKN2A homozygous deletion (HD) detected by FISH in pleural mesothelioma. The aim of our study was to evaluate the reliability of MTAP IHC as a surrogate marker for CDKN2A HD in peritoneal mesothelioma. Methods and results: Thirty‐nine FFPE tissue samples of PeM were analysed for CDKN2A copy number status by FISH. MTAP IHC was performed using antibody clone 2G4, and cytoplasmic positivity was evaluated using two different cut‐offs (1% and 30%). Agreement between IHC and FISH was assessed using Cohen's Kappa. A ROC curve analysis was performed to evaluate the overall diagnostic performance of MTAP IHC. McNemar's test was used to identify statistically significant discordance between the techniques, and a power analysis was conducted to confirm the adequacy of the sample size. Additionally, 14 benign peritoneal lesions were included as external controls and underwent both FISH and IHC. All control samples showed preserved MTAP expression and no CDKN2A deletion. CDKN2A HD was detected in 27/39 cases. MTAP loss was observed in 13 cases, while the remaining 26 cases showed variable levels of MTAP positivity (15%–100%; mean: 36.4%; median: 25%). Cohen's Kappa revealed a low, non‐significant concordance between MTAP IHC and CDKN2A HD (cut‐off 1%: Kappa = 0.091, P = 0.462; cut‐off 30%: Kappa = 0.083, P = 0.326). ROC curve analysis (AUC = 0.569) confirmed the poor discriminatory performance of MTAP IHC. McNemar's test showed a statistically significant discordance between MTAP IHC and CDKN2A FISH results. Power analysis confirmed that the sample size ( n = 39) was adequate. Conclusions: These findings may reflect biological and pathogenetic differences between pleural and peritoneal mesotheliomas. Larger, multicentric studies are needed to validate the diagnostic role of MTAP IHC in peritoneal mesothelioma.

Background: An increased risk of mesothelioma has been reported in various countries for construction workers. The Italian National Mesothelioma Registry, from 1993 to 2018, reported exposure exclusively in the construction sector in 2310 cases. We describe the characteristics of these cases according to job title. Methods: We converted into 18 groups the original jobs (N=338) as reported by ISTAT codes (‘ATECO 91’). The exposure level was attributed at certain, probable and possible in accordance with the qualitative classification of exposure as reported in the Registry guidelines. Descriptive analysis by jobs highlights the total number of subjects for each single job and certain exposure, in descending order, insulator, plumbing, carpenter, mechanic, bricklayer, electrician, machine operator, plasterer, building contractor, painter and labourer. Results: The cases grow for plumbing in the incidence periods 1993-2018, while, as expected, it decreases for insulator. Within each period considered the most numerous cases are always among bricklayers and labourers, these data confirm the prevalence of non-specialised "interchangeable" jobs in Italian construction sector in the past. Conclusions: Despite the 1992 ban, the construction sector still presents an occupational health prevention challenge, circumstances of exposure to asbestos may still occur due to incomplete compliance with prevention and protection measures.

The study describes the 466 cases of malignant mesotheliomas (MM) collected by the National Mesothelioma Register (ReNaM) in Italy in the period 1993-2018 relating to subjects with exclusive asbestos exposure in merchant or military navy. The cases among maritime workers represent 1.8% of the total cases with defined exposure registred in the ReNaM, of which 212 cases (45.4%) among merchant maritime workers and 254 cases (54.5%) among navy. The distribution by site of mesothelioma showed 453 (97.2%) MM cases of the pleura, 11 (2.3%) of the peritoneum and 2 (0.4%) of the tunica vaginalis of the testis. With regard to occupational exposure, it was classified as certain in 318 (68.2%) cases, probable in 69 (14.8%) cases and possible in 79 (16.9%) cases. Among the 23 classified jobs, the highest percentages of certain exposures are among naval engineers, motor mechanics, machine captains and sailors. Machine crew accounted for 49.3% of the cases, deck crew for 27.6%. All cases began exposure on board between 1926 and 1988. Seamen were exposed to asbestos while at sea by virtue of living onboard ships and from continual release of asbestos fibers due to the motion of a vessel. Epidemiological surveillance through the ReNaM has allowed us to verify among cases in the maritime, navy and merchant marine sectors, that in the past, subjects were exposed regardless of the ship's department where have provided service therefore all these cases must be considered as occupational diseases.

Background and Objectives: Radon is a known risk factor for lung cancer, and residential radon exposure is the leading cause of lung cancer in never smokers; however, in Italy, there is still a lack of public awareness regarding the risk caused by residential radon exposure. In this mortality study, which was carried out in an Italian Apulian town (Locorotondo) of the Bari province, we aimed to analyze lung cancer mortality and all-cause mortality in a population highly exposed to radon. Materials and Methods: The study period was 1998–2021. Local and Italian population and national mortality data were collected from the Italian National Institute of Statistics (ISTAT) website platform. Local mortality data were collected using copies of the Local Health Authority death certificates. Results: We identified 117 lung cancers in the studied period. The mortality data trends revealed a decrease in the all-causes standardized mortality ratios (SMRs), increases in the incidence rates of lung cancer and colorectal cancer in recent years, and a decrease in the incidence of noncancer diseases. We also found high SMRs for colorectal cancer until 2016 among older females. With respect to the cardio-circulatory system, only in 2014 did the male SMRs significantly influence the total SMR; after this period, a decreasing stable trend was observed. Conclusions: The natural balance of the population is decreasing, and mortality is decreasing for all causes. A future study will be needed to assess the associations between observed lung cancer cases and domestic radon exposure to drive radon mitigation and public health strategies.