Paraneoplastic cerebellar degeneration from an isolated nodal clear cell carcinoma of suspected gynecologic origin: case report and literature review.

Paraneoplastic cerebellar degeneration (PCD) is a rare neurologic syndrome that often presents before an underlying malignancy is diagnosed. Patients typically develop subacute cerebellar symptoms—such as vertigo, dysmetria, disconjugate gaze, and dysarthria—before any tumor is detected. Establishing the diagnosis involves ruling out metastatic disease, treatment toxicity, infection, and metabolic disturbances, and often hinges on finding antineuronal antibodies (most commonly anti-Yo, also called type-1 anti-Purkinje cell antibody or PCA-1) in blood or cerebrospinal fluid (CSF). Anti-Yo positivity is classically linked to breast or gynecologic cancers and carries a poor prognosis. We describe a 56-year-old woman with a remote history of parotid basal cell adenocarcinoma who developed gradually worsening cerebellar dysfunction over several months, despite negative initial imaging and routine laboratory tests. When more extensive antibody testing revealed high-titer anti-Yo antibodies in serum and CSF, our suspicion for a paraneoplastic process increased. Subsequent FDG-PET/CT identified FDG-avid pelvic lymph nodes, and surgical pathology confirmed metastatic clear cell carcinoma in two iliac nodes, although the uterus, ovaries, and fallopian tubes were entirely benign. The patient received plasma exchange, intravenous immunoglobulin (IVIG), high-dose steroids, and adjuvant carboplatin/paclitaxel. Although she experienced some improvement in speech and upper-limb coordination, she remains non-ambulatory with persistent cerebellar deficits, three years after initial presentation. This case illustrates how anti-Yo PCD can foreshadow an occult nodal gynecologic malignancy without an identifiable primary tumor, highlighting the need for an extensive workup—including advanced metabolic imaging and, sometimes, empiric surgical exploration—when initial evaluations are unrevealing. Early tumor localization and treatment of both the malignancy and autoimmune response remain crucial to optimizing neurologic outcomes.