A case of metastasizing pleomorphic adenoma in the maxillary bone appearing twenty years after initial resection of pleomorphic adenoma of the hard palate

Abstract

Metastasizing pleomorphic adenoma (MPA) is the inexplicable metastasis of a histologically benign pleomorphic adenoma (PA). Approximately 50 cases have been reported. A 62-year-old woman noticed pain in the upper molar area. Her medical history included an operation for PA in the hard palate that was performed 20 years previously. On imaging, four relatively well-defined lesions were demonstrated in the maxillary bone. She underwent an operation for these lesions. Each lesion revealed the same histological features. Morphological findings displayed typical features of PA. Immunohistochemical staining showed that tumor cells of both primary and metastasizing lesions were positive for pleomorphic adenoma gene (PLAG) 1, which is a sensitive marker for PA. Gene fusions involving PLAG1 were examined by reverse transcription-polymerase chain reaction. However, no gene rearrangements of PLAG1 were found. We report here on a case of MPA in the maxillary bone, which appeared 20 years after resection of the primary tumor and review the relevant literature.

Metastasizing Pleomorphic Adenoma Case Report and Review of the Literature

“…In one case of MPA, Alkiba et al, compared immunohistochemical expression of PLAG1 with rearrangement of PLAG1 by RT-PCR in both the primary PA and MPA. They found that both the primary PA and MPA were positive for PLAG1 protein but neither tumor harbored the PLAG1 fusion gene [42].…”

A unique case of benign pleomorphic adenoma metastasizing to the thyroid gland and liver

“…40%-73% of recurrent tumours are multifocal as compared to 0.14%-0.6% in primary untreated pleomorphic adenoma [1] . Renehan et al have reported bone as the most common site for metastases (45%) followed by the head and neck (43%) and lung (36%) [4] .…”

“…However, when PSAs recur, they are associated with poorer outcomes and prognosis [1] . Pleomorphic adenoma in the thyroid gland has been described previously: one case in the right thyroid lobe [2] and the other as an incidental midline isthmic thyroid nodule [3] .…”

Genomic copy number alterations of primary and secondary metastasizing pleomorphic adenomas

“…Three types of malignancy have been reported to be associated with pleomorphic adenoma (PA): carcinoma ex‐pleomorphic adenoma (CXPA), carcinosarcoma, and metastasizing pleomorphic adenoma (MPA). The last of these is the least common, and to date only 50 MPA cases have been reported . The mechanism of the metastatic behaviour of MPA is still unknown, and it is speculated that the accumulation of key genetic alterations drives cancer progression, which is not always accompanied by histological changes …”