Multiple Pulmonary Pleomorphic Adenomas of Unknown Primary

Abstract Introduction/Objective The most common site of pleomorphic adenomas (PAs) is salivary glands, which behave as benign tumors and rarely metastasize. Primary PAs in lungs are exceedingly rare. We report a case of multiple PAs in lungs with an inconclusive origin. Methods A 65-year-old woman had a two-year history of numerous scattered bilateral well-circumscribed pulmonary nodules measuring up to 2.1 cm. She had no prior history of smoking, asbestos exposure and salivary gland diseases, and denied any symptoms. The latest chest computed tomography (CT) scan showed the two largest lower lobe nodules had mildly increased in size compared to two years before. The patient then underwent wedge resections. Results Grossly, the wedge resection specimens showed multiple well-circumscribed, pale tan, firm nodules. Microscopically, the nodules comprised cytologically bland nests of polygonal to plasmacytoid cells with eosinophilic cytoplasm, variably set in a myxoid matrix. Immunohistochemical stains demonstrated that the cells were positive for AE-1/AE-3, S-100, bcl-2 and SOX-10, and negative for chromogranin, smooth muscle actin, p63, calponin, PAX-8, CD34, CD31, HMB-45, melan-A, HHF-35, GATA-3, GFAP and RCC marker; TTF-1 highlighted entrapped pulmonary epithelium but the tumor cells were negative. These findings might suggest metastatic low grade PA from salivary glands. However, the patient’s follow-up examination by an otolaryngologist was normal; the CT scan of her chest and abdomen did not show any remarkable findings other than her lung nodules. Conclusion To our knowledge, this is the first reported case of multiple pulmonary PAs without a preceding primary. It has raised questions about the pathogenesis of multiple PAs in lungs. Could PA present as multiple primary nodules in lungs? Could one primary pulmonary PA generate multiple satellite nodules in lungs? Do multiple primary pulmonary PAs have a different IHC profile than that of a single primary pulmonary PA? More research is needed.