PT  - JOURNAL ARTICLE
AU  - Toshiaki Kawai
AU  - Reishi Seki
AU  - Kuniharu Miyajima
AU  - Hiroshi Nakashima
AU  - Takayuki Takeda
AU  - Tomoyuki Murakami
AU  - Keisuke Aoe
AU  - Kazunori Okabe
AU  - Keiichi Homma
AU  - Yoshitane Tsukamoto
AU  - Koichi Sunada
AU  - Yasuhiro Terasaki
AU  - Maki Iida
AU  - Hideki Orikasa
AU  - Kenzo Hiroshima
TI  - Malignant pleural mesothelioma with heterologous elements
AID  - 10.1136/jclinpath-2021-207575
DP  - 2022 Oct 01
TA  - Journal of Clinical Pathology
PG  - 690--695
VI  - 75
IP  - 10
4099  - http://jcp.bmj.com/content/75/10/690.short
4100  - http://jcp.bmj.com/content/75/10/690.full
SO  - J Clin Pathol2022 Oct 01; 75
AB  - Aims Malignant pleural mesothelioma with heterologous elements (such as osseous, cartilaginous or rhabdomyoblastic differentiation) is very rare. We tried to differentiate such mesothelioma cases from extraskeletal pleural osteosarcoma, which is very challenging.Methods We compared 10 malignant pleural mesotheliomas (three biphasic and seven sarcomatoid types) with two pleural osteosarcomas using clinicopathological and immunohistochemical methods, and also fluorescence in situ hybridisation (FISH) to examine for homozygous deletion of p16.Results The median age was 72 years for mesotheliomas, and 69 years for osteosarcoma. For mesothelioma, eight cases were male and two were female. Growth was diffuse in all mesothelioma cases except case 10, where it was localised, as it was for the two osteosarcomas. Among mesothelioma cases, 80% displayed osteosarcomatous and 60% chondromatous elements, while 10% exhibited rhabdomyoblastic ones. Immunohistochemical labelling for calretinin and AE1/AE3 was present in 8/10 and 7/10 mesotheliomas, respectively, but in only one osteosarcoma. Loss of methylthioadenosine phosphorylase was seen in 5/7 mesotheliomas. FISH analysis revealed homozygous deletion of p16 in 5/8 mesothelioma and 2/2 osteosarcoma. Median survival was 6.5 months after biopsy or surgical operation in mesothelioma, and 12 months after operation in osteosarcoma.Conclusions Although median survival was longer for osteosarcoma than for malignant mesothelioma, we could not differentiate mesothelioma from pleural osteosarcoma on the combined basis of clinicopathological and immunohistochemical data, and FISH analysis. However, diffuse growth was more frequent in mesothelioma than in osteosarcoma.Data are available on reasonable request.