Benign metastatic mixed tumours or unrecognized salivary carcinomas?

Abstract

Abstract‘Benign metastasizing mixed tumours’ are enigmatic lesions of the parotid gland. The authors, through the illustrations of a case and review of the literature, conclude that the tumours are unrecognized and currently unclassified malignancies.

Metastasizing mixed tumour of the parotid gland presenting as multiple lung metastases

“…[1][2][3][4] One of the most important features of metastasizing mixed tumour is the association with recurrence; metastatic spread of the tumour is usually preceded by recurrent mixed tumour. [1][2][3][4][5][6][7] • Case report of a pleomorphic adenoma of the parotid, presenting with metastatic disease in the lung • The patient had had preauricular masses excised 17 and 23 years previously, pathology unknown • Previous cases have been reported; this case confirms the potential malignant nature of a disease generally considered to have a benign course…”

“…Common sites of metastasis are lung, bone, and sometimes liver and lymph nodes, suggesting that the tumour tends to metastasize haematogenously rather that lymphatically. [2][3][4][5][6][7][8][9] Although this type of tumour is considered pathologically benign, metastatic ability is generally a characteristic of malignant tumour. Moreover, relevance of molecular factors such as DNA ploidy, oncogene and tumour suppressor gene with the mechanism of metastatic potential of the tumour has not been elucidated.…”

Metastasising pleomorphic salivary gland adenoma presenting as synchronous pulmonary and hepatic metastases

“…Controversy regarding their classification exists due to the discrepancy between the histologically benign and biologically malignant behaviour 9. A history of histologically benign PAs in primary and secondary sites, however, is considered diagnostic 3.…”

???Metastasizing pleomorphic salivary adenoma??? should now be considered a low-grade malignancy with a lethal potential

“…El-Naggar et al [21] have reviewed cases reported previously and considered that there is both a lack of definition and also limitations of contemporary objective evaluations of pleomorphic adenomas. He also considered that there was a presence of atypical histologic features in the primary tumor or metastases of all reported cases, including their own, and thus raised the question of authenticity.…”

“…Flow cytometry analysis revealed a diploid DNA population in most cases [21], whereas aneuploidy was reported in a small group (2 of 11 patients) [10]. DNA ploidy may help identify more aggressive pleomorphic adenomas but even these are considered currently not totally predictive.…”