Carcinoma ex pleomorphic adenoma

Carcinoma ex pleomorphic adenoma is a carcinoma arising from a primary or recurrent benign pleomorphic adenoma, most often presenting as a firm parotid mass; it is difficult to diagnose preoperatively, pathological assessment is the gold standard, treatment is ablative surgery often followed by radiotherapy, prognosis is poor overall, and molecular studies show a multistep progression from adenoma (Head and Neck Pathology 2012). The WHO classification grades it by the extent of invasion beyond the adenoma capsule (intracapsular, minimally invasive, widely invasive), which drives prognosis. In 619 SEER patients the parotid was the site in 76.9 percent, two- and five-year disease-specific survival were 90.3 and 80.4 percent, facial nerve sacrifice did not predict survival, and size over 4 cm, multiple positive nodes and distant metastasis raised the risk of death two- to four-fold (American Journal of Otolaryngology 2019).

How it differs from its parent: the carcinoma component can be of any salivary type (salivary duct carcinoma most often), so treatment follows that component once invasion is established, and the history of a slowly growing lump that suddenly enlarges is the clinical clue.

How common: about 0.6 per million a year in the United States (American Journal of Otolaryngology 2019).

Treatment: complete excision (parotidectomy) for all forms; postoperative radiotherapy and neck dissection for widely invasive, high-grade or node-positive disease; systemic therapy by the carcinoma component, including HER2- and androgen receptor-directed therapy when the component is salivary duct carcinoma, as on that page.