Intrapulmonary solitary fibrous tumor: clinicopathological analysis of 29 cases with emphasis on morphological spectrum and immunohistochemical profile

Intrapulmonary solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm that can mimic pulmonary adenofibroma (PAF) when respiratory epithelium is entrapped. We retrospectively analyzed 29 intrapulmonary SFTs, reviewing clinical, histopathological, and immunohistochemical features. STAT6, CD34, ER, and PR were evaluated. The cohort included 18 males and 11 females (mean age 55.3 years); 69.0% were asymptomatic. Mean tumor size was 4.11 cm, with pleural attachment in 62.1%. Histologically, 79.3% showed biphasic cellularity, 86.2% had staghorn vessels, and 44.8% exhibited entrapped epithelium. Stromal changes included collagenization (89.7%), hemorrhage (24.1%), myxoid change (20.7%), cystic change (6.9%), and multinucleated giant cells (3.4%). Risk stratification identified 25 low-risk, three intermediate-risk, and one high-risk case. STAT6 was positive in all tested cases (28/28, 100%), and CD34 in 96.3%. Among 22 evaluable cases, 19 (86.4%) showed ER < PR. During a mean follow-up of 36.7 months, one high-risk patient (3.4%) developed local recurrence. Intrapulmonary SFT has a broad morphological spectrum with frequent epithelial entrapment as a key diagnostic pitfall. STAT6 is a reliable diagnostic marker, while ER < PR is common but of uncertain significance.