Metastatic salivary duct carcinoma presenting as cannonball lung lesions on radiology: Case Report

Abstract

Background: Salivary duct carcinoma (SDC) is a rare, aggressive salivary gland tumor with a high rate of metastasis and overall poor prognosis. SDC is commonly diagnosed at stage 3 or stage 4 with progression to local, regional lymph nodes or distant metastatic disease predominantly to the lung, bone, brain or skin. The case presents a 44 year old with an unusual presentation of distant metastasis appearing as cannon ball lesions in the lungs.Case presentation: The patient is a 44 year old male tobacco user with a history of recent incarceration who presented with a several month history of weight loss and enlarging right neck mass. He was found to have multiple bilateral lung masses with brain metastasis on imaging. Biopsy of the neck mass was consistent with salivary duct carcinoma with a rare basal-like phenotype. The patient was ultimately treated with targeted radiotherapy palliatively; however, he was not a candidate for chemotherapy due to extensive disease burden. He declined clinically and was transitioned to hospice care.Conclusions: The case provides a new presentation of an atypical salivary duct carcinoma with bilateral cannonball disease on imaging in addition to a rare histopathologic variant originating likely from an ex pleomorphic adenoma. The basal-like variant was found to have differing gene expression compared to the most commonly seen histological types. Considering the expression noted, the findings provide further information on the expression pattern of basal-like SDC for future targeted therapy and also clarify concerns with accurate diagnosis in SDC in comparison to other morphologically similar malignancies.