FROM THE PROSTATE TO THE LUNGS WITHOUT ANY BONY STOPOVERS

Abstract

TOPIC: Lung Cancer TYPE: Medical Student/Resident Case Reports INTRODUCTION: Lung metastases have been reported in over 40 percent of men with prostate cancer (1). One third to half of patients have metastasis at time of presentation with bone involvement in 90 percent of the cases. Prostate cancer that metastasizes to the lungs without any bone metastasis is a rare occurrence (2). CASE PRESENTATION: A 75-year-old male veteran presented with complaints of hemoptysis, weight loss, and fatigue for approximately three months. In regards to malignancy associated risk factors, he was a former smoker and had previous exposure to agent orange. Upon presentation, he had a history of prostate cancer, diagnosed 7 years prior and treated with brachytherapy and leuprolide injections in the setting of biochemical recurrence. Due to concern for recurrence of prostate cancer based on his current clinical presentation, he underwent a bone scan and DEXA scan, both of which did not reveal any lesions to suggest metastatic disease. Additionally, CT abdomen/pelvis revealed no evidence of periprostatic lesions, lymphadenopathy, or osteoblastic/osteolytic lesions. CT thorax showed multiple bilateral pulmonary lesions as follows: right major and minor fissure, right posterior medial pleural cavity with the largest cluster in the left lower lobe/major fissure measuring 3.6 x 2.7 x 2.7 cm. No definite lymphadenopathy or osseous lesions were identified. Patient then underwent a PET/CT scan, which confirmed bilateral FDG-avid pulmonary masses and showed borderline prominent FDG-avid mediastinal, right hilar, and right supraclavicular lymphadenopathy. At this time, with a high suspicion for a new primary malignancy rather than metastasis, the patient underwent CT-guided core biopsy of the left lesions followed by the right lesions two weeks later. The left lung biopsy demonstrated tumour cells strongly positive for TTF-1, negative for p40 which was consistent with adenocarcinoma of the lung. A diagnosis of new primary lung cancer was assumed until the right lung biopsy revealed carcinoma that was strongly positive for TTF-1 and NKX3.1, suggestive of malignant adenocarcinoma originating in the prostate. DISCUSSION: Although TTF-1 is often expressed in adenocarcinoma of the lung, it is not very specific and can be positive in adenocarcinomas from various anatomic sites. Meanwhile, NKX3.1 is not as sensitive but is very specific for prostatic carcinomas (3). Isolated lung metastases without concurrent bone or lymph node metastases is uncommon and only reported in a few published literatures. Diagnosis can be challenging, but is crucial in ensuring effective treatment for the patient. CONCLUSIONS: This case emphasizes the importance of considering prostate cancer in the differential diagnosis of male patients presenting with pulmonary nodules, even in the absence of bony metastasis. It also demonstrates the importance of immunohistochemistry in identifying the site of origin for cancer lesions. REFERENCE #1: Saitoh H, Hida M and Shimbo T (1984) Metastatic Patterns of Prostatic Cancer Correlation Between Sites and Number of Organs Involved Cancer 54 3078–3084 PMID: 6498785 REFERENCE #2: Kume H, Takai K, Kameyama S, Kawabe K. (1999) Multiple Pulmonary Metastasis of Prostatic Carcinoma with Little or No bone or Lymph Node Metastasis. Urologia Internationalis (62) 44-47. https://doi.org/10.1159/00003035 REFERENCE #3: Conner JR, Hornick JL. Metastatic Carcinoma of Unknown Primary: Diagnostic Approach Using Immunohistochemistry. Adv Anat Pathol. 2015 May;22(3):149-67. doi: 10.1097/PAP.0000000000000069. PMID: 25844674 DISCLOSURES: No relevant relationships by Man Dai, source=Web Response No relevant relationships by Jessica Gosse, source=Web Response No relevant relationships by Patricia Morissette, source=Web Response No relevant relationships by Steven Yi, source=Web Response