Metastatic Mucoepidermoid Carcinoma to the Pleura: An Unusual Presentation

Abstract

Abstract Casestudy Mucoepidermoid carcinoma is the most common malignant tumor arising in salivary glands. Predictors of poor prognosis include high-grade tumors, positive surgical margins, lymph node metastasis, or distant metastasis. The most common sites for distant metastasis include skin, lung, liver, and bone. We herein present a case of salivary gland mucoepidermoid carcinoma with pleural involvement, which is an infrequent site for metastasis. A 64-year-old female presented with worsening dyspnea and cough, which showed no improvement with antibiotics. Imaging showed a right lung nodule measuring 1.2 cm along with bilateral pleural effusion and pleural based nodularities. The dominant nodules in right and left chest measured 5.8 cm and 4.8 cm in greatest dimension, respectively. The findings were suspicious for metastatic disease. Cytological examination of pleural fluid showed reactive mesothelial cells and inflammatory cells. Subsequent biopsy of the right pleural nodule showed sheets of tumor cells with abundant eosinophilic cytoplasm and few scattered clear cells. Mucocytes were absent. The tumor cells were positive for p40 and negative for TTF-1 by immunohistochemistry. A review of patient’s medical history was significant for high-grade salivary gland mucoepidermoid carcinoma, which was resected and radiated six years prior. A comparison of both lesions showed similar morphologic features. Mucicarmine stain was positive in resection specimen but negative in pleural biopsy, confirming the absence of mucocytes. Molecular studies on both specimens showed positivity for fusion of CRTC1 (19p13) and MAML2 (11q21) loci. The overall findings were consistent with metastatic mucoepidermoid carcinoma to pleura. Conclusion Pleura is an uncommon site for metastasis from primary salivary gland mucoepidermoid carcinoma but should be part of differential diagnosis. Extensive review of patient’s past medical history plays a crucial role in correctly classifying these lesions as primary or metastatic. Differential diagnoses should include primary squamous cell carcinoma, mesothelioma, and the rare primary mucoepidermoid carcinoma of pleura.