A 62-year-old woman was referred with a 3-week history of a tender, rapidly enlarging lump in the left submandibular region. There was associated pain that radiated to the mandible and ipsilateral ear. Examination revealed a firm, mildly tender, approximately 33-cm mobile mass in the region of the submandibular gland. No other neck masses were palpable. Examination of the oral cavity failed to show any mass lesion in the floor of mouth, nor a lesion of the submandibular duct, and the duct papilla was noted to be normal. Full ear, nose, and throat examination was normal. As clinical evidence supported the diagnosis of an inflammatory or infective process, the patient was prescribed a week’s course of oral ciprofloxacin, and routine haematologic investigations and a floor-of-mouth radiograph were organized. This was subsequently reported as normal. Of the blood tests, only the erythrocyte sedimentation rate of 37 mm in 1 hour (normal, 5 to 15) and C-reactive protein of 13 mg/L (normal, 0 to 10) were abnormal. As the mass was unilateral and nonfluctuant, fine-needle biopsy was also arranged. The result of fine-needle assessment showed malignant cells consistent with aspiration from a non–small cell carcinoma. The cytologist was unable to comment on whether this was a primary lesion of the submandibular gland or a lymph node metastasis. Urgent computed tomography (CT) scans of the paranasal sinuses and chest, and magnetic resonance imaging of the neck were performed in an attempt to determine a potential primary site. In addition, the patient was admitted for a left tonsillectomy and panendoscopy, including biopsies of the postnasal space, base of tongue, and left piriform fossa. CT scan of the paranasal sinuses was normal. Negative histology of the biopsy samples and the left tonsil, coupled to the magnetic resonance imaging findings showing replacement of the left submandibular gland by tumor (Fig 1), suggested the left submandibular gland as the primary site. CT scan of the chest did, however, reveal a region of consolidation in the right posterior mid-zone. The remaining lung fields were clear. Following advice from our radiology colleagues as to the infective nature of the lesion, a 2-day of intravenous cefotaxime, followed by 5 days of oral cefadroxil, was prescribed. A chest radiograph 1 week later confirmed complete resolution of the lung lesion. The patient underwent surgical removal of the left submandibular gland and an ipsilateral selective neck dissection including removal of the deep cervical lymph nodes from levels I to IV. The neck dissection was performed to exclude micrometastatic disease in the locoregional cervical lymph nodes. Subsequent histologic examination of the resected specimen revealed a high-grade carcinosarcoma suggested by extension beyond the tumor pseudocapsule and vascular invasion. The epithelial component of the malignancy was adenocarcinomatous with glandular structures and mucus secretion (Fig 2). There was a predominantly sarcomatous component with regions of osteoid formation (Fig 3) and the presence of osteoclastlike giant cells, findings consistent with osteosarcoma. Further immunohistochemical staining showed neurofibrosarcomatous (S100), smooth muscle (smooth muscle actin), and striated muscle (myoglobin) elements, emphasizing the polyclonal histogenicity of these rare lesions. All lymph nodes excised with the specimen were free from malignancy. In light of the histologic findings, specifically the extracapsular spread and vascular invasion, as well as the expected aggressive nature of the tumor, the patient was treated with postoperative radiotherapy of 66 Gy in 33 daily fractions of 2 Gy. She currently remains well and free of disease 12 months after treatment.