Oral pseudotumor: benign polypoid masses following radiation therapy

The current study evaluated postirradiation pseudotumor in the oral cavity to investigate clinical and pathologic characteristics and incidence rates.

Between 1960 and 1999, 2719 patients with squamous cell carcinoma of the oral cavity were treated with radiation therapy at Tokyo Medical and Dental University Hospital. Of these, six patients developed clinically polypoid tumors pathologically diagnosed as pseudotumors. Histopathology, immunohistology, and the clinical courses of these lesions were investigated.

Spindled fibroblastic cells arranged in whorled patterns were common pathologic features. Immunohistochemical results showed reactivity for vimentin and smooth muscle actin and nonreactivity for cytokeratin. The latent period from the initial radiation therapy to the development of the pseudotumor ranged from 45 to 145 months (median, 79 months). The overall cumulative incidence of pseudotumor was 0.22% during the 40 year period. All six patients were cured with simple excisions.

Oral carcinoma patients treated with radiation therapy may develop pseudotumor in a low frequency with a shorter period than that of radiation induced carcinoma/sarcoma. Pseudotumor was curable with surgery. Pseudotumor should be added to the list of differential diagnosis for postirradiation oral polypoid masses.