Metastatic Basal Cell Carcinoma: An Unexpected Diagnosis in a Young Patient With Back Pain.

Basal cell carcinoma (BCC) portends a notoriously favorable prognosis in most patients with morbidity limited to localized destruction and recurrence. Metastatic BCC (mBCC) is an unexpected outcome affecting less than 1% of patients with a known primary lesion and predominantly involves regional lymph nodes. Reports of isolated bone involvement and spinal cord compression are rare. In the cases we identified in the literature, patients presented with massive primary lesions on the trunk that had been present for years and that were often still present at the time of diagnosis. Additionally, histology of distant metastatic lesions typically reveals aggressive subtypes. Herein, we report a case of mBCC in a patient with a history of BCC involving the cheek; the lesion was excised more than 10 years ago. He was referred to our institution for acutely worsening back pain and multifocal neurologic deficits. Clinical symptoms and radiographic findings demonstrated isolated bone involvement, with multiple lytic bone lesions and spinal cord compression noted on imaging studies. Biopsy revealed nests of small basaloid cells with peripheral palisading and immunohistochemical staining consistent with the unexpected diagnosis of mBCC, nodular subtype. Our case illustrates that a historically resected primary lesion may cause distant metastasis after a decade and that nonaggressive subtypes can also be implicated. We also provide insight into the potential pathogenesis of this manifestation.