Metastasizing mixed tumor of the parotid: Initial presentation as a solitary kidney tumor and ultimate carcinomatous transformation at the primary site

Magdalena Czader, Charles G. Eberhart, Nasir Bhatti, Charles Cummings, William H. Westra

Research output: Contribution to journalArticle


Benign mixed tumors of the salivary glands are generally regarded as indolent and harmless neoplasms. A subset of benign mixed tumors, however, can undergo carcinomatous transformation (that is, carcinoma ex-mixed tumor). Even more rarely, a mixed tumor that is seemingly benign at the microscopic level will metastasize like a true carcinoma (that is, metastasizing mixed tumor [MZMT]). Despite the benign appearance of the metastatic implants, there is usually little doubt regarding their true nature and origin. Patients invariably have had a mixed tumor removed from the parotid or some other salivary gland, and metastatic spread is usually preceded by multiple episodes of local tumor recurrence. We report a case of MZMT that presented as a solitary kidney mass. In the absence of a previous or concurrent salivary gland tumor, its metastatic nature was not appreciated and it was regarded as an unusual but benign kidney adenoma. One year after removal of the kidney mass, the patient presented with signs and symptoms of an aggressive parotid tumor. Pathologic examination of the tumor in the parotid demonstrated a high-grade carcinoma arising from a mixed tumor. This case underscores the importance of considering MZMT when a seemingly benign mixed tumor is encountered at a nonsalivary site, even in patients without a supportive history. Failure to do so may cause an unnecessary delay in primary tumor diagnosis and management, allow the primary tumor to progress toward a more malignant phenotype, and deny the patient a high expectation for a complete cure.

Original languageEnglish (US)
Pages (from-to)1159-1164
Number of pages6
JournalAmerican Journal of Surgical Pathology
Issue number8
StatePublished - Aug 1 2000



  • Carcinoma ex-mixed tumor
  • Kidney tumor
  • Malignant ex-mixed tumor
  • Malignant ex-pleomorphic adenoma
  • Malignant mixed tumor
  • Metastasizing mixed tumor
  • Parotid
  • Pleomorphic adenoma
  • Salivary gland tumor

ASJC Scopus subject areas

  • Anatomy
  • Surgery
  • Pathology and Forensic Medicine

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