60. Isolated pulmonary metastatis from prostate adenocarcinoma eighteen years after primary resection

Abstract

Background Solitary pulmonary metastasis from prostate adenocarcinoma is rare, with only 18 described cases in the English literature. Most pulmonary metastases from prostate adenocarcinoma show microacinar and ductal patterns, and are likely to feature cribriform architecture. However, a cribriform pattern can also occur in primary lung adenocarcinoma, and immunostains are required to differentiate between the two. We report a case of an elderly man with an isolated left lower lung nodule, which was shown to be metastatic prostate adenocarcinoma. This illustrates the importance of considering prostatic metastasis when assessing a solitary lung lesion. Case report An 86-year-old man presented with a left lower lobe lung nodule found on CT and FDG-PET, on a background of radical prostatectomy in 1995 for adenocarcinoma (T2aN0M0, Gleason 4 + 4). His recent PSA levels were mildly raised (6.91 in September 2013). However, there were no osseous lesions. A primary lung lesion was therefore suspected, and he underwent left lower lobectomy. Histopathology showed a 28 mm lesion, with cribriform and papillary architecture and focal intraluminal necrosis. In view of the suggestive morphology, immunostaining for PSA and AMACR were performed; these were positive. Staining for CK7, CK20, TTF1, Napsin A, EGFR (exons 19,21) and ALK1 were negative. This confirmed metastatic prostate adenocarcinoma, with mixed ductal and acinar patterns (Gleason 4 + 5 = 9). Post-operatively, the patient made a good recovery, and his PSA level fell rapidly (0.05 in February 2014). Conclusion Although rare, solitary pulmonary metastasis from prostate adenocarcinoma can occur, even more than a decade after initial excision. Therefore, this should be considered as a differential when evaluating a pulmonary lesion.