罕見病例報告 - 去勢抵抗性前列腺癌發現眼筐轉移腫瘤

吳冠儒¹、林文榮¹

¹台灣基督長老教會馬偕醫療財團法人馬偕紀念醫院泌尿科

Orbital Metastasis in Castration-Resistant Prostate Cancer (CRPC) with Atypical Differentiation: A Case Report

Kuan-Ju Wu¹, Wun-Rong Lin ¹

¹Department of Urology, MacKay Memorial Hospital, Taipei, Taiwan

Introduction –

Metastatic Prostate Carcinoma commonly involves bone, lymph nodes, and visceral organs like the lung or liver. However, metastasis to the orbit is an extremely rare clinical event, often indicating an aggressive course of the disease. This report presents a 77-year-old male with known metastatic Castration-Resistant Prostate Cancer (mCRPC) who developed a rapidly progressing left orbital mass, leading to ocular symptoms. The case highlights the unusual presentation of prostate cancer progression and the challenges in managing advanced mCRPC refractory to sequential hormonal and cytotoxic therapies.

Case presentation –

The patient is a 77-year-old male with a history of mCRPC (Gleason score 9, pT3aN0M0, positive margin). His prior management included Radical Robotic-Assisted Laparoscopic Prostatectomy (RALP, 2022/01), Salvage Radiotherapy (sRT) to the prostate fossa (2022/03–05), Androgen Deprivation Therapy (ADT) since 2022/03, two cycles of Taxotere (Docetaxel) chemotherapy, and the initiation of a second-generation anti-androgen, Xtandi (Enzalutamide), in August 2024. The patient also has comorbidities of HTN, DM type 2, and Parkinsonism.

The chief complaint was left eye protrusion, blurred vision, and diplopia noted since September 24, 2025. Serial PSA monitoring showed a progressive rise from <0.02 ng/mL in January 2025 to 0.62 ng/mL in October 2025.

Result –

Orbital CT performed on June 16, 2025, revealed a newly developed 3.6 x 2 cm mass in the upper extraconal space of the left eyeball with bone erosion of the orbital roof of the frontal bone. A follow-up Brain MRI on October 20, 2025, showed rapid progression to an approximately 5-6 cm heterogeneously enhancing mass in the left orbital extraconal space, with adjacent bone erosion and dural enhancement, confirming a rapidly progressing malignancy.

A Trans-orbital tumor biopsy was performed on October 21, 2025. The pathology confirmed the mass as metastatic carcinoma. Immunohistochemical analysis was highly suggestive of prostatic origin: the tumor cells were positive for CK, NKX3.1, and Androgen Receptor (AR), while negative for PSMA, LCA, GFAP, and melan-A. Additionally, the tumor exhibited neuroendocrine markers (synaptophysin, INSM1, chromogranin A positive), suggesting aggressive features or neuroendocrine differentiation. The final diagnosis was Left orbital metastatic carcinoma (5 cm), suspected prostatic origin.

Discussion –

Orbital metastasis from prostate cancer is exceptionally rare, often signifying high tumor burden and aggressive biology, such as the emergence of small cell or neuroendocrine prostate cancer (NEPC). The patient's clinical course—progression despite ADT, chemotherapy (Docetaxel), and a second-generation anti-androgen (Xtandi) therapy—confirms a difficult-to-treat mCRPC status. The rapid growth of the orbital mass, combined with the immunohistochemical staining profile (positive for AR, NKX3.1, and neuroendocrine markers), raises concern for aggressive variant prostate cancer (AVPC) or small cell transformation, which is refractory to typical ADT.

The therapeutic plan must now shift to agents effective against this aggressive phenotype, potentially involving platinum-based chemotherapy (e.g., Carboplatin/Docetaxel or Cabazitaxel) or disease-state specific therapy for aggressive variant cancer, as per NCCN guidelines. Local radiation therapy to the orbit may also be considered for palliation of ocular symptoms, given the patient's rapidly expanding mass. The tissue proof and molecular profiling are essential steps for guiding next-line systemic therapy in this challenging case of late-stage mCRPC.

Image –

Figure 1. Orbital CT showed newly developed 3.6*2 cm mass at upper extraconal space of the left eyeball with bone erosion.

Figure 2. Brain MRI showed an about 5-6cm heterogeneously enhancing mass in left orbital extraconal superior and lateral location with erosive change of adjacent bone and dural enhancement at left frontal base and left anterior temporal region.