Solitary Lung Metastasis From Primary Prostate Cancer With Normal Prostate Specific Antigen Level: a Case Report and Literature Review

Background: Pulmonary involvement from prostate cancer is a well-known condition, but solitary lung metastasis is rare, with its associated clinical characteristics not yet fully elucidated.Case presentation: A 77-year-old man, with a history of radical prostatectomy for primary prostatic carcinoma 14 years prior, presented to our institution with a low-grade fever. Upon consultation, biochemical recurrence was suspected due to a gradual increase in prostate-specific antigen level. Salvage radiation therapy was considered but not performed since there was no recurrent macroscopic tumor. Computed tomography showed a solitary nodule with spiculation located on the upper lobe of the left lung while positron emission tomography suggested malignancy without metastasis. Based on these findings, primary lung cancer was suspected and thoracoscopic left upper lobectomy with lymph node dissection was performed. Pathological diagnosis of the tumor was a solitary lung metastasis of prostate cancer. The postoperative recovery was uneventful. Conclusion: We report a case with normal prostate-specific antigen level, along with a literature review. According to previous case reports, there are some pitfalls leading misdiagnosis as a primary lung tumor. However, we consider that surgical resection is associated with increased diagnostic accuracy and long-term survival.