Objective To investigate the clinicopathologic features, diagnosis and differential diagnosis of pulmonary selerosing pneumocytoma (PSP). Methods A total of 13 cases of PSP were enrolled, and the clinical and imaging findings, pathologic features, and immunophenotype were collected and analyzed, with review of the literatures. Results Thirteen patients were all female, aged from 27 to 69 years old by first discovered, the average age was 53 years old. The maximum diameter ranged from 0.8 - 6 cm. It was mainly discovered accidentally by physical examination. According to the CT findings of 13 cases, all lesions were round or round-like, with a well-circumscribed mass. The “welt vessel sign” was suggestive to the diagnosis of PSP. Microscopically, the tumor was composed of two types of cells (surface epithelial cells and round mesenchymal cells), and four histological patterns (papillary, solid, hemorrhagic and sclerotic zone). Immuophenotype: thyroid transcription factor-1 (TTF-1) and epithelial membrane antigen were expressed on both epithelial cells and mesenchymal cells. Pan cytokeratin (PCK) and cytokeratin 7 were only expressed on epithelial cells, and vimentin on mesenchymal cells. Conclusion PSP is a rare lung benign tumor, preoperative and intraoperative freezing diagnosis are difficult, the diagnosis depends on the morphologic characteristics of paraffin-embedded tissue sections and immunohistochemical staining. The identification of mesenchymal cells with TTF-1 positive and PCK negative is the key to PSP diagnosis.
