Microscopic vessel caliber patterns in pulmonary thromboembolism: Clinical and autopsy correlations in a 10-year autopsy series.

To evaluate the relationship between microscopic pulmonary thromboembolism (PTE) patterns and clinical and autopsy variables in a large autopsy series. A retrospective review of 18,585 autopsies performed between 2014 and 2023 was conducted, from which 304 cases with PTE were included. Macroscopic and histopathological findings were compared, and microscopic involvement was categorized into large-, medium-, and small-caliber arterial patterns. Associations between clinical characteristics, circumstances of death, and autopsy variables were analyzed using chi-square test and multinomial logistic regression. Macroscopic examination was highly sensitive for the detection of large-vessel PTE (91.9%) but had markedly lower sensitivity for medium- and small-caliber arterial involvement (14.3% and 3.8%, respectively). Microscopic arterial patterns were significantly associated with history of surgery, infection, cerebrovascular events, place of death, autopsy period, and deep vein thrombosis (DVT) evaluation (p < 0.05). No significant associations were observed with sex, age, or major chronic diseases. The absence of macroscopic DVT evaluation and in-hospital death were independently associated with medium- and small-caliber arterial patterns in multinomial regression analysis. Microscopic vascular distribution of PTE is associated with clinical and autopsy-related factors. Macroscopic examination alone may underestimate the involvement of medium- and small-caliber pulmonary arteries. Systematic histopathological evaluation is essential for accurate diagnosis and characterization of PTE.