A case report in primary intraosseous Squamous cell carcinoma arising from a dentigerous cyst

Dentigerous cysts are one of the most common cysts of the mandible. They are frequently seen surrounding lower third molars which have seen chronic inflammation and extraction has been avoided. We report a case of a 59-year-old male with an intraosseous squamous cell carcinoma from a lesion which clinically looked like a dentigerous cyst.

He was referred by his General Dental Practitioner to our oral surgery department for extraction of a symptomatic LL8 in June 2023. His initial CBCT scan showed abnormalities including destruction of the buccal and lingual plate and was referred urgently to our local oral and maxillofacial unit due to risk of mandible fracture. He had no paraesthesia.

His referral was then upgraded to a 2 week wait pathway by our oral and maxillofacial consultant after the patient saw him privately in October 2023 and was planned for a biopsy under General anaesthetic in November 2023. However, he sustained a pathological fracture of his mandible 4 days prior to his surgery. An OPG was taken at this point showing significant increase in size of the lesion.

A biopsy was taken from the mucosa around the LL7 and a separate biopsy from the intraosseous lesion. The histology from the central lesion biopsy confirmed it was a moderately differentiated squamous cell carcinoma, but the mucosal biopsy showed no signs of dysplasia.

This patient subsequently had a segmental mandibulectomy and fibular free flap reconstruction in January 2024, 2 weeks after his biopsy. The histology of the resection was now a poorly differentiated squamous cell carcinoma.

This highlights an unusual case of an aggressive malignant tumour where there was no mucosal ulceration or dysplastic features. It emphasises the importance of reassessing the patient’s clinical picture and to be aware of the potential malignant change of odontogenic cysts.