A80-3-18 Beyond the Bruise: Metastatic Male Breast Cancer Masquerading as Post-Traumatic Pleuropericardial Effusions

Introduction Accounting for less than 1% of all breast cancer cases, male breast cancer remains a rare and often overlooked entity, frequently diagnosed at advanced stages. Its atypical presentations are easily mistaken for unrelated conditions, leading to diagnostic delay. We present a case of pleuro-pericardial effusions initially attributed to alternative etiologies, which ultimately revealed underlying metastatic male breast cancer. Case Description A 49-year-old man with no prior medical history presented to the emergency department with one week of nausea, vomiting, abdominal discomfort, chest pressure, and exertional dyspnea. On arrival, he was tachycardic and tachypneic, appearing mildly distressed but maintaining oxygenation on room air. A rapid SARS-CoV-2 test returned positive, raising concern for an infectious or inflammatory process.Physical examination revealed jugular venous distention and a 3 × 2 cm clean ulcer with granulation tissue over the left anterior chest wall, just superior to the areola. The patient attributed it to chest wall trauma three weeks earlier while playing basketball, when a hard lump developed at the site and later ulcerated. His dyspnea was initially positional, worsening when lying on the left.Bedside ultrasound revealed bilateral pleural effusions and a moderate pericardial effusion. CT confirmed a large left-sided pleural effusion occupying nearly the entire hemithorax with collapse of the underlying lung, as well as a smaller right effusion, hepatic and skeletal lesions, and moderate ascites. Because the left pleural fluid appeared echogenic and possibly hemorrhagic, the patient was transferred to a trauma center for emergent thoracentesis.Thoracentesis yielded straw-colored fluid, later confirmed cytologically as malignant. Biopsy of the ulcerated chest wall lesion demonstrated invasive ductal carcinoma of the breast, estrogen- and progesterone-receptor positive, HER2 negative, consistent with metastatic hormone-receptor-positive male breast cancer. The patient has since required serial thoracenteses and paracenteses and is currently receiving endocrine and targeted therapy. Discussion The history of trauma served as a diagnostic red herring, steering attention toward hemothorax and delaying recognition of malignancy. This case underscores the importance of reconsidering initial assumptions when findings diverge from expected patterns. Even seemingly trivial injuries can coexist with, or distract from, serious underlying disease processes such as metastatic male breast cancer. References: 1. Karmakar S, Chaudhuri T, Nath A, Neyaz Z. Male Breast Cancer Presenting with Bilateral Pleural Effusion. North Am J Med Sci. 2013;5(1):72-74. PMC2. El Ouali Z, Id El Haj N, Boubia S, Elkebir A, Karkouri M, Ridai M. A Case of Male Breast Cancer Relapsing with Pleural Effusion. PAMJ Clin Med. 2019;1:3.