Objective To explore the clinicopathologic features of ciliated muconodular papillary tumors (CMPT).

Methods Eight CMPT patients with complete clinical data were selected from Xinhua Hospital, Dalian University and the First Affiliated Hospital of Dalian Medical University from January 2017 to December 2018, the clinical characteristics, histopathological features, immunophenotype, molecular pathology, and differential diagnosis were analyzed.

Results Among the 8 patients, the ratio of male to female was 1:7, and the mean age was 63.5 years, there was no dominant sex or location. The first symptoms were all lung space occupying found in physical examination, and imaging manifestations were ground-glass opacity (GGO). Histologically, the neoplasm is composed of ciliary cells, basal cells, and mucous cells. Note the lacustrine formation and papillary structures. Immunohistochemistry showed ciliary columnar cells and mucous cells cytokeratin (CK7) (+), thyroid transcription factor-1 (TTF-1) (+), NapsinA (+ or -); Basal cells P63 (+), P40 (+), CK5/6 (+); epidermal growth factor receptor (EGFR) (+) was weakly expressed in most of the tumor cells, and EGFR was detected by AMRS PCR. Exon 19 was absent in 1 of 6 cases (1/6, 1.7%). AB-PAS (+) with mucous staining, and elastic fiber staining showed loss or destruction of the alveolar elastic framework. All cases were treated by surgical resection without recurrence or metastasis.

Conclusions CMPT is a rare benign tumor, which is easy to be misdiagnosed as mucinous adenocarcinoma. By correctly recognizing ciliated cells and the continuous expression of basal cell markers, the misdiagnosis rate of the disease can be reduced.