Primary salivary gland squamous cell carcinoma with sialolithiasis in the submandibular gland: A case report and literature review

Primary salivary gland squamous cell carcinoma (SCC) is a very rare malignancy, and such a tumor with sialolithiasis is even rarer. Here, we report a case of 68-year-old man with primary salivary SCC and sialolithiasis. A cystic lesion with a salivary stone was found in the submandibular gland, lined by atypical epithelium with focal invasive focus. The atypical epithelium was positive for cytokeratin 5/6 and p40, and focally positive for p63, cytokeratin 14 and periodic acid-Schiff (PAS) stain. S-100 protein, calponin, α-smooth muscle actin, SOX10 and androgen receptor were negative and no mucin-containing cells were found on PAS with diastase and Alcian blue staining. The Ki-67 labeling index was relatively high. P53 was mostly negative, and no pathogenic TP53 mutations were detected. The diagnosis of primary salivary gland SCC was made. In our review including the present case, the speculated cause of primary salivary gland SCC was squamous metaplasia and dysplasia due to chronic irritation by a salivary stone. Although no cases with recurrence or distant metastasis were identified, more cases and long-term follow-up are needed.