Lipoma: A benign tumor composed of fat tissue, which can present as a palpable, cyst-like mass and is consistent with the normal neck ultrasound and thyroid findings.

Cystic Hygroma: A congenital anomaly that can present as a cyst-like mass in the neck, although it's more common in children, it can also be diagnosed in adults.
Branchial Cleft Cyst: A congenital anomaly that can present as a cyst-like mass in the neck, typically anterior to the sternocleidomastoid muscle.
Thyroglossal Duct Cyst: A congenital anomaly that can present as a midline or slightly off-midline cyst-like mass, although the normal thyroid ultrasound makes this less likely.

Metastatic Lymph Node: Although the neck ultrasound is normal, it's essential to consider the possibility of a metastatic lymph node, especially if there's a history of cancer.
Parathyroid Adenoma: A benign tumor of the parathyroid gland that can present as a palpable mass, although it's typically smaller and more commonly associated with hyperparathyroidism.
Thyroid Nodule: Although the thyroid ultrasound is normal, it's crucial to consider the possibility of a thyroid nodule, especially if there are any symptoms of thyroid dysfunction.

Dermoid Cyst: A rare congenital anomaly that can present as a cyst-like mass in the neck.
Teratoma: A rare tumor that can contain several different types of tissues and present as a cyst-like mass in the neck.
Carotid Body Tumor: A rare tumor of the carotid body that can present as a palpable mass in the neck, although it's typically more lateral and associated with the carotid artery.