Discussion
Prostate cancer is the third leading cause of cancer death in men.4 It is the most common non-cutaneous cancer in men in the United States.5 It typically affects males above the age of 50. However, younger age groups have been identified since using P.S.A. as a screening tool.6 The five-year survival rate of localized and regional prostate cancer is more than 99%, whereas metastatic prostate cancer is only 30%1. At presentation, about 78% of the lesions are localized, and only 6% of cases present with metastasis.1 Spread to other body parts usually occurs through lymphatic, hematogenous, or direct extension. Bone and lymph nodes are common sites among those with metastatic lesions, with pulmonary, hepatic, retroperitoneal, or abdominal metastasis very uncommon.6 Mediastinal metastasis is exceedingly rare and can present with mediastinal adenopathy in 0.6% of the cases.7 Only one other case of prostate cancer is reported presenting with a mediastinal mass.8 In the United States, significant racial differences exist in the management of prostate cancer.9
Management initially begins with screening, either by measuring P.S.A. once a patient reaches above the age of 50 or performing a digital rectal examination to check for a palpable abnormality.6 Confirmatory tests involve performing an ultrasound-guided transrectal prostate biopsy in a grid-like pattern and staging it based on Gleason’s scoring.10 Even though it is the standard of care, it can miss up to 28% of lesions and undergrade up to 17%.11 Hence, newer diagnostic tests, biomarkers, and imaging modalities have been developed to improve diagnosis and risk stratification accuracy.10 One such biomarker that is specific to primary prostatic adenocarcinoma is NKX3.1.12,13, coded for by a gene located on chromosome 8p, which aids prostate development and acts as a tumor suppressor gene. Loss of this marker correlates with microenvironment inflammation, usually found in the early stages of prostate cancer.14
Studies have also shown that NKX3.1 interacts with M.Y.C., and a reduction in the former results in proliferative effects of M.Y.C., leading to cancer progression and relapse.15 It can also distinguish between high-grade prostate cancer and high-grade bladder cancer.16 It can be used to identify metastasis and has shown a sensitivity and specificity of 98.6 and 98.7% respectively in a cohort of metastatic tumors.17 Studies have also shown that it is more specific than P.S.A. when identifying prostate cancer.18 Based on our discussion, our case also has similar pertinent findings. Our patient was an African American male aged 68 years with a late diagnosis due to patient non-compliance; a biopsy of his metastatic mass was positive for NKX3.1. Even though a digital rectal exam or a prostate-specific antigen due to the absence of genitourinary symptoms and a different presentation, a diagnosis was confirmed based on immunohistochemistry. Since his primary symptoms improved his condition was further managed on an outpatient basis with the hematology-oncology team.
Author Contributions:
1, Muhammad Haider - Department of Medicine, Richmond University Medical Center/Mount Sinai
Prepared, reviewed and edited the manuscript
2, Arun Umesh Mahtani- Department of Medicine, Richmond University Medical Center/Mount Sinai
Reviewed and edited the manuscript/figures
3, Bachar Botrus - Department of Medicine, Richmond University Medical Center/Mount Sinai
Reviewed and edited the manuscript/figures
4, Foma Munoh Kenne - Department of Hematology/Oncology, Richmond University Medical Center/Mount Sinai
Reviewed and edited the manuscript
5, Madiha Fatima Master - Philadelphia College Of Osteopathic Medicine
Reviewed and edited the manuscript