A 70-year-old woman, never-smoker, presented with right upper quadrant abdominal pain and nausea. She had no known oncologic history. CTA chest showed a polylobular solid nodule in the right lower lobe measuring 3.9 cm (Figure 1). PET scan showed mild metabolic activity within the lung nodule (maximum SUV of 4.5), and no other sites of abnormal metabolic activity. A CT-guided biopsy was performed (results not shown), and she subsequently underwent a thoracoscopic right lower lobectomy. Gross examination revealed a well-circumscribed, tan-white, firm nodule that detached from the lung parenchyma during surgical retrieval. Microscopic examination showed a nodular growth pattern with alternating fibrotic and myxoid areas at low magnification (Figure 2). There were several large collagen rosettes with hyalinizing fibrosis (Figures 3 and 4). Higher magnification revealed bland spindle cells arranged in a swirling storiform pattern within fibromyxoid stroma (Figure 5). No increased mitotic activity or tumor necrosis was present. Immunohistochemical stains showed neoplastic cells were positive for MUC4 (Figure 6) and negative for pan-cytokeratin, desmin, SOX10, STAT6, DOG1, and beta-catenin.

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