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May 22, 2026Open Access

A case of pleomorphic adenoma with pseudoepitheliomatous hyperplasia mimicking a malignant tumor

YSYoshimasa SumitaNiigata University HHHideaki HiraiJCR Pharmaceuticals (Japan)YSYuko SAITONiigata University

Key Points

The aim is to highlight a case of pleomorphic adenoma with pseudoepitheliomatous hyperplasia that was initially suspected to be malignant.
Patient diagnosed with pleomorphic adenoma and pseudoepitheliomatous hyperplasia based on clinical evaluation and imaging.
Imaging techniques included PET-CT showing high FDG uptake and suspected invasive characteristics.
Histopathological examination and immunohistochemical staining were performed to assess malignancy markers.
Patient presented with palatal swelling and rapid tumor growth over eight years with ulcer formation.
Immunohistochemical findings showed no p53 overexpression or increased Ki-67 positivity, indicating benign behavior.
No recurrence observed in the 14 months following surgery.

Abstract

Pleomorphic adenoma is the most common benign tumor arising in the salivary glands and generally has a favorable prognosis.However, malignant transformation has been reported in long-standing or recurrent cases, as well as in elderly patients or tumors of large size.In contrast, pseudoepitheliomatous hyperplasia refers to a state in which the epithelium shows marked hyperplasia, representing a benign reactive change that can be easily misinterpreted as squamous cell carcinoma both clinically and histopathologically.We report a case of pleomorphic adenoma with pseudoepitheliomatous hyperplasia that was strongly suspected to be malignant based on clinical and radiological findings.The patient was a 28-year-old man who had noticed palatal swelling for eight years but had left it untreated.He presented after recent rapid tumor growth accompanied by ulcer formation.Imaging revealed suspected invasion of adjacent structures and high FDG uptake on PET-CT, strongly suggesting malignancy.Initial biopsy findings raised suspicion of squamous cell carcinoma; however, histopathological examination of the resected specimen led to the diagnosis of pleomorphic adenoma with pseudoepitheliomatous hyperplasia.Immunohistochemical staining showed neither p53 overexpression nor an increase in Ki-67-positive cells.There has been no recurrence during the 14 months following the operation.

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