Mucinous Carcinoma in a Male: First Documented Case in Nicaragua.

Breast malignancy in men is an exceedingly rare condition, representing a small fraction of all diagnosed breast cancer cases. The most common histological subtype is invasive ductal carcinoma, while the mucinous type is extremely rare. This pathology has a high mortality rate due to its poor prognosis and diagnosis in advanced stages, often initially overlooked with limited screening. Surprisingly, more men have died from breast cancer than from testicular cancer. This report details a case of invasive mucinous carcinoma in a 75-year-old male who presented with a five-week history of chronic non-productive cough and signs of pleural effusion. A breast magnetic resonance imaging (MRI) revealed a retroareolar breast tumor, and a second-look ultrasound confirmed the presence of a BI-RADS 4C solid nodule. Histopathological and immunohistochemical results were confirmed by ultrasound-guided tru-cut biopsy, identifying invasive mucinous carcinoma and luminal B (HER2+) subtype. Staging studies were negative for metastasis, and a modified radical mastectomy was performed, yielding favorable intraoperative findings. The incidental diagnosis in this patient highlights the necessity of comprehensive imaging in atypical presentations. Despite its rarity, awareness and early detection of mucinous carcinoma are essential for optimizing patient outcomes. This case also underscores the disparity in breast cancer outcomes between low gross domestic product (GDP) and high-GDP countries, emphasizing the need for improved access to diagnostic and therapeutic resources. Enhanced clinical awareness and early detection are crucial for improving outcomes in patients with rare histological subtypes, particularly in underserved regions.