A rare case of Porphyromonas endodontalis lung abscess mimicking lung cancer on imaging: the diagnostic value of postoperative metagenomic next-generation sequencing.

This case highlights the diagnostic challenge of a Porphyromonas endodontalis lung abscess mimicking lung cancer. A 67-year-old male presented with a right lower lobe mass suggestive of malignancy. Following wedge resection, pathology confirmed an abscess. Metagenomic next-generation sequencing (mNGS) of the tissue revealed a microbial profile dominated by oral anaerobes of Porphyromonas endodontalis. Postoperative mNGS identified the oral origin of infection and prompted periodontal treatment, leading to full recovery. This report reveals the decisive value of postoperative mNGS in correcting a diagnosis of infection mimicking lung cancer. It emphasizes that oral anaerobic infections can present as "tumor-like" pulmonary lesions. This case suggests that oral infection sources should be considered in the differential diagnosis of challenging pulmonary lesions and highlights the potential value of a multidisciplinary approach that includes dental evaluation.