Primary Gastrointestinal Stromal Tumor Presenting as an Isolated Lung Mass

Gastrointestinal stromal tumors (GISTs) are rare gastrointestinal (GI) tumors, representing a small portion of soft tissue tumors of the abdominal cavity. Extraintestinal gastrointestinal stromal tumors (EGISTs) are uncommon forms of GISTs that present outside the GI tract. There have only been a rare number of reported cases of EGIST presenting above the diaphragm. We present the case of a 50-year-old female with shortness of breath, and found to have bilateral pleural effusions and left-sided lung mass. The initial lung mass aspiration was negative for malignancy; yet, pleural fluid was suggestive of malignancy, and repeat biopsy and immunohistochemical stain were diagnostic for GIST. Ultimately, the patient underwent video-assisted thoracoscopic surgery, pleurodesis with doxycycline, and adjuvant therapy with imatinib. This is a report of primary EGIST presenting as an isolated lung lesion with no involvement of the GI tract. In patients with suspected malignancy, it is of paramount importance to obtain a detailed history, including remote signs and symptoms, while performing a thorough work-up. Especially in the lung where initial biopsies can be skewed due to inflammation and atelectasis, repeat biopsies may be necessary to obtain an accurate diagnosis.