PT - JOURNAL ARTICLE AU - Zhanxian Shang AU - Yuchen Han AU - Jinchen Shao AU - Lei Zhu AU - Haohua Teng AU - Jie Zhang TI - Challenging of frozen diagnoses of small sclerosing pneumocytoma AID - 10.1136/jclinpath-2020-206729 DP - 2021 Nov 01 TA - Journal of Clinical Pathology PG - 730--734 VI - 74 IP - 11 4099 - http://jcp.bmj.com/content/74/11/730.short 4100 - http://jcp.bmj.com/content/74/11/730.full SO - J Clin Pathol2021 Nov 01; 74 AB - Aims An increasing number of small pulmonary nodules are being screened by CT, and an intraoperative diagnosis is necessary for preventing excessive treatment. However, there is limited literature on the frozen diagnosis of small sclerosing pneumocytomas (SPs). In particular, tumours smaller than 1 cm are challenging for pathologists performing intraoperative frozen diagnosis.Methods In total, 230 cases of SP were surgically resected between January 2015 and March 2019 at Shanghai Chest Hospital, and of them, 76 cases were smaller than 1 cm. The histology and clinical information of these 76 cases (33.0%, 76/230) were reviewed retrospectively, 54 cases of which were diagnosed intraoperatively, and the pitfalls were summarised. All diagnoses were confirmed on permanent sections and immunohistochemical sections.Results Histologically, 78.9% (60/76) of the small SP was dominated by one growth pattern, and solid and papillary growth pattern were the most commonly misdiagnosed circumstances. The rate of intraoperative misdiagnosis of these SP smaller than 1 cm was 11.1% (6/54).Conclusions The main reason for misdiagnosis was failure to recognise the dual cell populations and the cellular atypia. Diagnostic clues include the gross morphology, the presence of dual-cell populations and a hypercellular papillary core, foam cell accumulation in glandular spaces and haemorrhage and haemosiderin on the periphery. In spite of awareness of pitfalls some cases may still be essentially impossible to diagnose on frozen section.All data relevant to the study are included in the article.