Pituitary Adenoma: This is the most common cause of a sellar mass. The description of the mass being T1 hypo to iso and T2 iso to hypointense on MRI, and its involvement with the cavernous sinus, is consistent with a pituitary adenoma, especially a non-functioning or functioning adenoma that has grown to involve surrounding structures.

Meningioma: Meningiomas can occur in the sellar region and may involve the cavernous sinus. They are typically T1 iso to hyperintense and T2 iso to hyperintense but can have variable appearances. Their involvement with the cavernous sinus and dural tail sign on imaging can help differentiate them from pituitary adenomas.
Craniopharyngioma: Although more commonly seen in the suprasellar region, craniopharyngiomas can extend into the sellar region. They are often heterogeneous on MRI due to cystic components and calcifications, which can help distinguish them from other sellar masses.
Granular Cell Tumor: These are rare tumors of the sellar region but can involve the cavernous sinus. They are typically T1 iso to hyperintense and T2 hyperintense.

Lymphoma: Although less common, lymphoma can present as a sellar mass and involve the cavernous sinus. It is crucial to consider lymphoma due to its different treatment approach and prognosis. Lymphoma is typically T1 iso to hypo and T2 iso to hypointense.
Metastasis: Metastatic disease to the sellar region, including the pituitary gland and cavernous sinus, can occur. The imaging appearance can be variable, but the clinical context (e.g., known primary malignancy) is key to suspecting metastasis.
Invasive Macroadenoma with Cavernous Sinus Involvement: While pituitary adenomas are the most common diagnosis, an invasive macroadenoma with cavernous sinus involvement is critical to identify due to its implications for treatment and prognosis.

Germ Cell Tumors: These can occur in the sellar and suprasellar regions, especially in young males. They are often iso to hyperintense on T1 and hyperintense on T2-weighted images.
Chordoma: Although more commonly found in the clivus, chordomas can extend into the sellar region. They are typically T1 hypo and T2 hyperintense with a characteristic "honeycomb" appearance on MRI.
Rathke's Cleft Cyst: While not typically involving the cavernous sinus, large Rathke's cleft cysts can extend into the sellar region and may have a variable appearance on MRI, often with high signal on T1 due to proteinaceous content.