A potential new entity pending further validation of pulmonary primary interstitial Tumor: Lymphangioleiomyomatosis-like.

Primary pulmonary interstitial tumors represent a group of lung diseases. We encountered a case of a pulmonary primary interstitial tumor not previously reported in the literature. Based on existing research, this disease cannot be classified into any known subtype. We propose this disease as a potential new entity pending further validation-Pulmonary Primary Interstitial Tumor-Lymphangioleiomyomatosis-like (PIT-LAM). Histologically, this tumor is located within the interstitium, exhibiting abundant small blood vessels with spindle-shaped tumor cells surrounding them. While morphologically resembling lymphangioleiomyomatosis and hemangioblastoma, the immunohistochemical expression patterns differ. This paper provides a detailed description and analysis of clinical data, pathological examination, immunohistochemistry, along with incorporating a differential diagnostic analysis to advance understanding and foster novel insights into this condition.