Malacoplakia of the tongue complicating the site of irradiation for squamous cell carcinoma with review of the literature.

Malacoplakia is a benign and uncommon inflammatory response that develops most frequently in the genitourinary tract but has been reported at other sites. We report the case of 67-year-old man who presented with a lesion at the base of the tongue 7 months after chemoradiation for biopsy-proven invasive squamous cell carcinoma of the tongue. The lesion showed intense avidity by positron emission tomography and was biopsied with the putative clinical diagnosis of recurrent malignancy. Histologically, the lesion showed the characteristics of malacoplakia as well as abundant intracellular gram-negative bacilli. Ultrastructural analysis revealed giant lysosomes, intracytoplasmic calcific concretions (Michaelis-Gutman bodies), and partially digested gram-negative bacilli within vacuolated lysosomes of macrophages. To our knowledge, this is the seventh reported case of malacoplakia of the tongue and the first to develop at the site of prior radiation treatment of a carcinoma. The clinical features of this case, a review of previously reported cases, and a consideration of pathogenesis are presented.