A 56-year-old male patient with diabetes presented with black discolouration of the tongue 7 days after extraction of two mandibular molars (Fig. 1). Prophylactic oral amoxicillin 750 mg was started a day before the extraction and was continued for 4 days after extraction. Post-extraction, because of severe pain in the socket, he did not eat properly or maintain good oral hygiene. We collected a sample from the tongue lesion and performed a cytological analysis. Fragments of filiform papillae with markedly enhanced keratinisation were observed on microscopic examination of the scraped specimen.