以膀胱腫瘤表現之轉移性肺癌：罕見病例報告

梁柏崧 張建祥

彰化基督教醫院外科部泌尿外科

Incidental finding of metastatic lung cancer by urinary bladder tumor: A Rare Case Report

Po-Sung Liang, Jian-Xiang Chang 

Division of Urology, Department of Surgery, Changhua Christian Hospital

Introduction:

Metastatic lung adenocarcinoma with metastases to the urinary bladder represents a rare clinical scenario. Lung adenocarcinoma often spreads to bone, liver, adrenal glands, and brain, but seldom to the urinary bladder. Urinary bladder metastases from lung cancer sometimes cause hematuria and may be misinterpreted for primary bladder malignancy due to clinical and radiologic similarities. Pathological confirmation and immunohistochemical profiling (e.g., TTF-1, Napsin A positive) are needed to identify metastatic lung adenocarcinoma from original bladder cancer or other secondary malignancies.

Case presentation:

A 56-year-old with hypertension and papillary thyroid cancer post thyroidectomy presented with right flank and worsening lower back pain. Renal ultrasonography showed right hydronephrosis. Intravenous pyelography showed poor right kidney excretion and bladder wall irregularity. There was no radio-opaque calculi on KUB.

Computer tomography (CT) indicated focal bladder wall thickening, right UVJ encasement, and hydronephrosis. Cystoscopy showed a solid mass at the trigone with external compression to the right ureterovesical junction (UVJ). Biopsy was performed, and the pathology showed pleomorphic polygonal tumor cells in the stroma. Immunohistochemistry demonstrated TTF-1 (+), CK7 (+), Napsin A (+), thyroglobulin (-), PAX-8 (-), GATA-3 (-), CK20 (-), BRAFV600E (-), p40 (-), and ambiguous p16 nuclear staining with enhanced Ki-67 labeling. These data suggested invasive lung adenocarcinoma rather than original urothelial carcinoma or recurrent thyroid malignancy.

Further staging investigations followed. A 1.1 cm right upper lobe pulmonary nodule with mediastinal and hilar lymphadenopathy was seen on chest CT. Bone scans showed several osseous metastases, while PET showed adrenal and gastrointestinal metastases. Intracranial lesion was excluded by brain magnetic resonance imaging (MRI). Epigastric pain persisted during follow-up. Panendoscopy revealed a gastric lesion, and the pathology of biopsy also showed metastatic adenocarcinoma, and the immunohistochemical profile matched the lung primary. These results classified the disease as lung adenocarcinoma with urinary bladder, stomach, and bone metastases, cT1bN3M1c2 (stage IVB).

The patient started Osimertinib treatment after tumor tissue molecular testing revealed an EGFR exon 19 deletion mutation. She underwent thoracic spine and rib palliative radiation, then she had significant bone pain relief after the therapy. 1 month later, renal ultrasonography showed hydronephrosis resolution, suggesting regression of the bladder involvement under systemic therapy. 2 months later, follow-up chest CT also showed regression of the primary lung lesion. This case showed that targeted therapy and systemic disease control could reverse metastatic bladder-related obstructive uropathy.

Conclusions:

Urinary bladder metastasis originating from lung adenocarcinoma is uncommon and may closely resemble primary bladder cancer. This case highlights that obstructive uropathy without hematuria may be the initial presentation, prompting urologists to consider secondary malignancy in the differential diagnosis of bladder tumors. Immunohistochemistry and molecular testing are essential for precise diagnosis and treatment selection. Effective systemic treatment, exemplified by Osimertinib in this patient, may also ameliorate urological problems such as hydronephrosis, thus obviating the need for unneeded invasive operations.