A80-3-40 Flu Exposure Leads to Discovery of Cannonball Lung Lesions: A Diagnostic Challenge

Cannonball lung lesions are defined as multiple, well-circumscribed lung nodules seen diffusely on imaging. As the lungs are highly vascular, they are more vulnerable to metastatic emboli which creates this radiologic pattern. This finding represents disseminated malignancy and often carries a poor prognosis, especially when discovered on initial presentation. Common primary tumors associated with cannonball metastases are those with abundant venous outflow into systemic circulation including germ cell tumors, choriocarcinoma and endometrial cancer. Other primary sites have been noted in literature including hepatocellular carcinoma, gastric cancer and melanoma. We present the case of a 56-year-old female found to have cannonball lung lesions on initial presentation. She presented for influenza testing after recent exposure and reported only cough and dyspnea for two days, she was otherwise asymptomatic. Chest Xray and CT chest revealed extensive cannonball lung metastases, and further imaging revealed benign-appearing uterine fibroids but no other significant abnormalities. Multiple lung biopsies were performed including a lymph node biopsy, and the origin of her metastatic disease was initially thought to be bronchogenic carcinoma with squamoid and neuroendocrine features. Although lung to lung cannonball metastases is rare, it has been described in the literature. Subsequent immunohistochemical staining revealed focally positive PR with negative ER, PAX-8 and CA-125. The tissue additionally stained positive for CDX2 and CD 5/6, colonic and squamous markers respectively. This characterization failed to establish a definitive lineage and final pathology was determined as poorly differentiated high-grade carcinoma with squamous differentiation. The patient declined rapidly, and she unfortunately passed away. Molecular testing was not performed. This case highlights the unique imaging features of cannonball metastases as well as the diagnostic and therapeutic challenge posed by advanced, poorly differentiated disease. We compare similar cases with overlapping histologic profiles and discuss the importance of healthcare access and patient education in preventing such advanced presentations.