T2 Shine-Through Phenomenon in a Plunging Ranula

Abstract

Aim This case report aims to demonstrate a case of T2 shine-through using MRI and clinical features in a patient with a plunging ranula. Case Report In this report, a 16-year-old male presented with a left submandibular space expansion and a painless intraoral cystic lesion near the caruncula sublingualis. Clinical signs pointed towards a plunging ranula. MRI revealed a hypointense, well-defined lesion in T1 images and a hyperintense lesion extending from the sublingual gland through musculus mylohyoideus to the submandibular space, featuring a characteristic tail sign in T2 images. Notably, diffusion-weighted (DWI) TRACE images and apparent diffusion coefficient (ADC) images both displayed a hyperintense lesion, indicative of T2 shine-through. The combined evaluation of fine-needle aspiration cytology and imaging led to the diagnosis of a plunging ranula, and the patient was referred for surgical intervention by the oral and maxillofacial surgery department. Discussion The differential diagnosis of lesions can be aided by DWI and ADC values. T2 shine-through, as seen in this case, manifests as hyperintensity on both DWI-TRACE and ADC images, distinct from diffusion restriction. This phenomenon arises from prolonged T2 decay time in specific tissues. Similar instances have been noted in epidermoid cysts and, as illustrated here, in a plunging ranula. Conclusion Dentomaxillofacial radiologists should be attuned to the T2 shine-through effect, which can lead to misinterpretation when assessing lesions using DWI-TRACE and ADC sequences. This case underscores the need for accurate differentiation between diffusion restriction and T2 shine-through, enabling informed treatment choices.

Keywords

• Apparent diffusion coefficient
• Diffusion weighted imaging
• Magnetic resonance imaging
• Plunging ranula
• T2 shine-through

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