Solitary late spinal metastasis from apocrine salivary duct carcinoma: Case report

Background: The salivary duct carcinomas (SDCs) are rare, high-grade neoplasms involving major salivary glands. Parotid is the most frequently involved gland (85%). Apocrine phenotype (histological presence of decapitation secretions) and androgen reception expression define SDC. The clinical course of these tumors is characterized by aggressive local behavior with extraglandular extension, high recurrence rates, early metastases, and poor prognoses. Despite aggressive surgical/radiation therapy management, the rates of locoregional and metastatic relapses are high, and the mortality rates over 48 months approach 65%. Notably, there is no treatment algorithm available for managing vertebral metastases from apocrine SDC. Case Description: An elderly male presented with MR/CT findings of an isolated T11 vertebral metastasis attributed to a previously treated parotid SDC. On both CT/MR, it was an osteolytic lesion and demonstrated spinal canal infiltration. The patient underwent surgical biopsy/decompression/resection, following which the lesion histopathologically proved to be a SDC. The patient was subsequently treated with 30 Gy in 10 fractions within 2 weeks of discharge. One-month later, the MRI confirmed adequate epidural decompression without recurrence, and 9 months post-operatively, patient remained disease free. Conclusion: Isolated metastasis attributed to parotid SDC followed by radiation therapy may result in tumor control.