Identification of CTNNB1-PLAG1 gene rearrangement in a patient with pulmonary pleomorphic adenoma.

Pulmonary pleomorphic adenoma (PA) is a rare salivary gland-type neoplasm, which predominantly occurs in the proximal airway. Rearrangement of the pleomorphic adenoma gene 1 (PLAG1) is the most frequent genetic event in PAs of salivary glands. However, whether pulmonary PA also harbors PLAG1 rearrangement has not been elucidated. Here, we present a case of pulmonary PA, located at the middle lobar bronchus, in a 54-year-old man. CTNNB1-PLAG1 gene fusion was identified by reverse transcription-polymerase chain reaction using formalin-fixed paraffin-embedded tissue (FFPE). Furthermore, immunohistochemical analysis revealed nuclear expression of PLAG1 in all tumor cells. To the best of our knowledge, this is the first reported case of pulmonary PA with CTNNB1-PLAG1 fusion and PLAG1 expression. Our case illustrates the possibility that pulmonary PA could be underpinned by recurrent PLAG1 translocations akin to salivary gland PA.