Differential Diagnosis for New Diffusion Restricting Mass

Single Most Likely Diagnosis

• Squamous Cell Carcinoma: This is the most likely diagnosis given the location of the mass in the anterior right parotid and its association with the inferior aspect of the maxillary sinus, right portion of the palate, and dehiscence. The expansile FLAIR hyperintense soft tissue thickening and diffusion restriction are consistent with an aggressive tumor.

Other Likely Diagnoses

• Mucoepidermoid Carcinoma: A common salivary gland malignancy that can present as a mass in the parotid gland and can have aggressive features such as invasion into surrounding structures.
• Adenoid Cystic Carcinoma: Another type of salivary gland malignancy that can present with perineural invasion and aggressive features, although it is less common than squamous cell carcinoma in this location.
• Lymphoma: Can involve the parotid gland and surrounding structures, although it is less likely to cause bony dehiscence.

Do Not Miss Diagnoses

• Malignant Otitis Externa: Although less likely, this diagnosis can be deadly if missed, especially in diabetic or immunocompromised patients. It can cause significant destruction of surrounding tissues and bone.
• Necrotizing Fasciitis: A rare but life-threatening infection that can cause rapid destruction of tissue and bone, and can be associated with a parotid mass.

Rare Diagnoses

• Pleomorphic Adenoma with Malignant Transformation: A rare type of salivary gland tumor that can undergo malignant transformation, although it is less likely to cause aggressive features such as bony dehiscence.
• Metastatic Disease: Rarely, a metastatic lesion from a distant primary can present as a mass in the parotid gland and surrounding structures.
• Sarcoma: A rare type of malignancy that can occur in the parotid gland or surrounding soft tissues, although it is less common than other diagnoses listed above.