Carcinoma ex Pleomorphic Adenoma — MFDS Part 1 MCQ

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ModerateOral PathologyCarcinoma ex Pleomorphic AdenomaMFDS Part 1

A 68-year-old patient has a parotid swelling that enlarged slowly for 15 years but has recently increased rapidly in size and caused facial nerve weakness. Histopathological examination shows residual pleomorphic adenoma adjacent to an invasive high-grade epithelial malignancy. What is the most likely diagnosis?

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Correct answer: C — Carcinoma ex pleomorphic adenoma

The diagnosis is **carcinoma ex pleomorphic adenoma**, a carcinoma arising within a primary or recurrent pleomorphic adenoma. The long-standing, previously slow-growing parotid mass followed by rapid enlargement and facial nerve dysfunction suggests malignant change; the decisive finding is an invasive epithelial malignancy adjacent to residual pleomorphic adenoma. Carcinosarcoma ex pleomorphic adenoma contains both malignant epithelial and malignant mesenchymal components, which are not described here. Polymorphous adenocarcinoma, adenoid cystic carcinoma and acinic cell carcinoma are separate salivary malignancies and do not require a pre-existing pleomorphic adenoma. Prognosis depends particularly on factors such as the extent of invasion and tumour stage rather than simply the presence of a carcinomatous component.

Reference: Antony J, Gopalan V, Smith RA, Lam AKY. Carcinoma ex pleomorphic adenoma: a comprehensive review of clinical, pathological and molecular data. Head and Neck Pathology. 2012;6(1):1–9. https://pubmed.ncbi.nlm.nih.gov/21744105/