Cutaneous metastatic mucin-producing prostate adenocarcinoma

Ahmet Miguel Yildirim¹Douglas Semler²Jeffrey Harvell¹Eun-Mi Yu³Sekwon Jang³Suraj Venna^3*

• ¹Inova Fairfax Hospital, Falls Church, United States
• ²Semler Dermatology Inc., Landsdowne, United States
• ³Inova Schar Cancer Institute, Fairfax, United States

Introduction Prostate cancer is the most common cancer in men in the United States (excluding skin cancer) and the 2nd leading cause of cancer-related death following lung cancer.1 Patients with advanced prostatic adenocarcinoma (PAC) typically present with genitourinary or musculoskeletal symptoms due to tumor burden in the pelvis and bones. PAC is associated with distinct immunologic profiles.2 Metastatic PAC to the skin is rare and can present as an ulcerated skin nodule, typically on the trunk. We report a case of a metastatic mucin-producing PAC initially presenting as an ulcerated skin nodule. Case report A 91-year-old white male with a history of benign prostatic hypertrophy (BPH) presented to his dermatologist for a skin examination for an unrelated complaint. On exam, an ulcerated pink-to-skin colored nodule was noted on the right upper back (Fig 1). Histology from a punch biopsy from the edge of the nodule revealed a dermal-based malignant glandular tumor (Fig 2). Immunohistochemistry (IHC) was negative for CK20, CK5/6, PAX-8, TTF-1, as well as the prostate specific markers, PSA and PIN4. Lesional cells were positive for the prostate markers PSAP and NKXC3, consistent with a mucin-producing adenocarcinoma (Fig 3). Two months earlier, he had undergone a digital rectal exam (DRE) which was reported as normal. Based on his age, prostate cancer screening with a prostate-specific antigen (PSA) test was initially deferred and he resumed tamsulosin for his BPH. Metastatic work-up included a whole-body PET/CT which showered multiple hypermetabolic lesions, including the left scapula, axial spine, mediastinal lymph nodes, and an enlarged prostate. Serum PSA level was obtained and found to be elevated to 30.49 ng/ml. These findings were compatible with a metastatic, mucin-producing PAC. The patient began androgen deprivation therapy with relugolix, a GnRH