抄録
We report an interesting case of microinvasive carcinoma ex pleomorphic adenoma (PA) showing focal recurrence ten months after surgery, which on initial presentation was misdiagnosed as PA with atypia. A 45-year-old woman was admitted to our hospital, presenting with a painless mass in the left cheek that had been present for six years but had increased in size recently. With the clinical diagnosis of benign cheek tumor, a simple tumorectomy was performed. Initially, this tumor was pathologically diagnosed as pleomorphic adenoma (PA) with atypia showing capsular invasion. The patient received no chemotherapy or radiotherapy, but recurrent tumor was found in the left cheek 10 months after surgery, and a second tumorectomy was performed. Pathology of the recurrent tumor revealed PA with atypia or adenocarcinoma not otherwise specified (NOS), and therefore immunohistochemical staining of HER2 / neu was conducted for a differential diagnosis. In atypical foci of the primary tumor and the entire recurrent tumor, atypical cells showed moderately distinct membrane staining of HER2 / neu. This indicated that the primary tumor was microinvasive carcinoma ex PA, and the recurrent tumor was adenocarcinoma NOS. We concluded that immunohistochemical staining of HER2 / neu should be performed to obtain the correct diagnosis in PA cases with atypia.
