Metastasis from parotid gland cancer: Given the patient's history of low-grade parotid gland cancer, even with clean margins after surgical removal, there's a possibility of metastasis. The mildly enhancing nature of the C-spine spot could be consistent with a metastatic lesion, especially if the primary cancer had a propensity for spread.

Benign tumor (e.g., meningioma, schwannoma): These are common spinal tumors that can present as mildly enhancing lesions on imaging. They are often incidental findings but can be significant depending on their location and size.
Inflammatory or infectious process: Conditions like discitis, osteomyelitis, or an epidural abscess could present with enhancement on imaging due to inflammation. The clinical context (e.g., fever, pain) would help differentiate these from neoplastic processes.
Vascular malformation: Arteriovenous malformations (AVMs) or other vascular anomalies could appear as enhancing lesions due to their vascular nature.

Spinal cord lymphoma: Although less common, lymphoma can involve the spine and present as an enhancing lesion. It's crucial to consider this diagnosis due to its significant implications for treatment and prognosis.
Leptomeningeal metastases: If the patient's parotid gland cancer has spread to the leptomeninges, it could present with enhancing lesions along the spinal cord or nerve roots. This diagnosis has a profound impact on management and prognosis.
Spinal epidural hematoma: While often presenting acutely, a chronic epidural hematoma could potentially appear as a mildly enhancing lesion, especially if there's a history of trauma or anticoagulation.

Hemangioblastoma: A rare, benign tumor that could present as a mildly enhancing lesion, often associated with von Hippel-Lindau disease.
Spinal cord glioma: Primary spinal cord tumors are rare and could present with variable enhancement patterns on imaging.
Sarcoidosis: Neurosarcoidosis can involve the spine and present with enhancing lesions due to granulomatous inflammation.