Adrenal Adenoma: This is the most likely diagnosis given the description of the mass. Adrenal adenomas are common benign tumors of the adrenal gland, and while they are typically small, larger ones can occur. The presence of a solid component does not necessarily indicate malignancy, as some adenomas can have solid areas.

Pheochromocytoma: Although less common than adenomas, pheochromocytomas are another type of adrenal tumor that can present with a solid component. They are usually benign but can cause significant morbidity due to excessive catecholamine production.
Myelolipoma: This is a rare, benign tumor of the adrenal gland composed of fat and hematopoietic cells. It can grow large and may contain solid components, making it a consideration in the differential diagnosis.

Adrenal Cortical Carcinoma: This is a malignant tumor of the adrenal cortex. Although less common than adenomas, it is crucial to consider due to its potential for aggressive behavior and poor prognosis if not treated early.
Metastasis to the Adrenal Gland: The adrenal glands are a common site for metastases from other cancers, such as lung, breast, or melanoma. A large adrenal mass with a solid component could represent a metastatic lesion, especially in patients with a known history of cancer.

Ganglioneuroma: A rare, benign tumor that arises from the sympathetic nervous system and can involve the adrenal gland. It typically presents as a large, solid mass.
Neuroblastoma: Although more common in children, neuroblastoma can occur in adults and may present as a large adrenal mass with solid components. It is a malignant tumor that requires prompt diagnosis and treatment.
Lymphoma Involving the Adrenal Gland: Primary or secondary involvement of the adrenal glands by lymphoma can occur, presenting as a large mass with solid components. This diagnosis is rare but important to consider, especially in patients with a history of lymphoma or immunocompromised states.