BACKGROUND: Primary pulmonary sarcoma is extremely rare and mostly metastatic, and primary pulmonary myxoid sarcoma PPMS is a rare low-grade malignant sarcoma. The clinical manifestations of PPMS patients are relatively non-specific, sometimes found by physical examination. We report a case designed to explore the clinicopathologic features, diagnosis, and differential diagnosis of primary pulmonary myxoid sarcoma (PPMS). A 44-year-old man was found to have a primary myxoid sarcoma in the upper right lung on physical examination. The patient did not have any symptoms of discomfort. Histologically, the tumors had well-defined borders, and with grayish-white or grayish red cut surfaces. Under the microscope, the tumor cells were composed of oval and spindle cells arranged in a network or strips in a mucus-like stroma. Immunohistochemically, neoplastic cells showed diffuse and strong vimentin expression and focal weak EMA, and Bcl-6 staining. The expression of AE1/AE3, ALK, CD34, CD68, SMA, and CD99 were all negative. The Ki-67 index was low.
CONCLUSIONS: PPMS is a rare low-grade malignant primary pulmonary sarcoma without characteristic clinical symptoms and difficult to diagnose. It is mainly diagnosed by immunohistochemistry and genetic testing.

Primary pulmonary myxoid sarcoma (PPMS) is a recently described, exceedingly rare low-grade lung sarcoma that tends to present in young females as an endobronchial mass and shows evidence of an EWSR1- CREB1 fusion. Herein, we present a case of PPMS with fluorescence in situ hybridization (FISH) analysis for EWSR1 and CREB1 rearrangements. An 80-year-old woman presented with an endobronchial, multinodular tumor exhibiting spindle, ovoid and epithelioid cells arranged in reticular/lattice-like and alveolar-like patterns in a myxoid background. The tumor showed focal epithelial membrane antigen immunoreactivity as well as an Alcian blue-positive stroma that was sensitive to digestion with hyaluronidase. EWSR1 and CREB1 rearrangements were detected by break-apart FISH probes. The patient showed persistence of disease 36 months after diagnosis and was discharged to hospice care. We contribute with a report of an additional case of this very unusual entity and perform a brief review of the literature published so far on the subject.