Oral Actinomycosis Mimicking Recurrent Buccal Mucosa Squamous Cell Carcinoma Following Surgery and Adjuvant Radiotherapy: A Diagnostic Challenge

Actinomycosis is an uncommon chronic suppurative infection caused by filamentous, gram-positive, predominantly anaerobic bacteria of the genus Actinomyces, which are normal commensals of the oral cavity. Cervicofacial disease is the commonest presentation, whereas isolated oral mucosal involvement is rare. Previous surgery, radiotherapy, and poor oral hygiene disrupt the mucosal barrier and predispose to infection, and the resulting indurated, non-healing ulcer can closely mimic recurrent malignancy. Awareness of this entity among clinicians is limited, and misdiagnosis may lead to unnecessary radical treatment. We report a 51-year-old man with previously treated right buccal mucosa squamous cell carcinoma (SCC) who presented with a painful non- healing oral ulcer, difficulty in chewing, and progressive trismus after surgery and adjuvant radiotherapy. Multiple empirical antibiotics had failed, and clinical examination raised strong suspicion of recurrent carcinoma. Histopathological examination of repeated punch biopsies demonstrated hyperplastic squamous epithelium with granulation tissue containing characteristic Actinomyces colonies, with no evidence of dysplasia or invasive malignancy. Anaerobic culture showed no growth. The patient received intravenous ceftriaxone and clindamycin for one week, followed by three months of oral antibiotics, meticulous oral hygiene, local wound care, and mouth-opening exercises, with gradual clinical improvement and no histological evidence of recurrent carcinoma. Clinicians should maintain a high index of suspicion, and oral actinomycosis should be considered in the differential diagnosis of any persistent oral lesion after treatment of head and neck cancer. Histopathological confirmation before a lesion is labelled as recurrent malignancy avoids unnecessary radical surgery and allows effective, prolonged antimicrobial therapy.