Squamous cell carcinoma (SCC) of the lip is one of the most common head and neck malignancies. It has a high survival rate; however, it poses an uncommon risk of metastasis. This almost universally manifests in the cervical lymph nodes, with lip SCC having the lowest incidence of distant metastasis among cancers of the head and neck. Notably, this subset of patients demonstrates the highest chance of cancer-related mortality. There are virtually no reports in the literature of organ metastasis from lip SCC to date. Herein we present a rare and unusual case of metachronous renal metastasis from SCC masquerading as a primary renal neoplasm.

A 72-year-old male was referred in early 2025 with a large left renal mass detected on CT, ordered after he developed lower left sided abdominal and flank pain. He had no haematuria, weight loss or other systemic symptoms. His renal function was impaired with a creatinine of 115 mmol/L. His history included an SCC of the lip, requiring left neck dissection to treat nodal recurrence of disease. He received immunotherapy with tislelizumab between 2016 and 2018 and responded completely. Surveillance CT scans had demonstrated no sign of recurrence or progression as of October 2023. The large mass in the left kidney measured 78x60x77mm with complete effacement of the renal sinus. A 7mm nodule was noted at the left lung base that was consistent with metastasis. A subsequent CT chest revealed multiple lung nodules measuring up to 10mm on the left and 6mm on the right lung. FDG PET scan demonstrated a large cystic and necrotic lesion in the left kidney with high avidity (SUV max of 14.6). There was suspected adjacent perinephric lymph node involvement. Notably, there was no local tumour recurrence of the patient’s SCC in the head or neck. Given the size of the lesion relative to the small lung nodules, and a solitary renal metastasis being an exceedingly rare site of spread for SCC, it was presumed that the kidney lesion was a new malignancy of renal origin. A robotic assisted left radical nephrectomy was performed. During dissection, gross inflammation was noted around the upper pole of the kidney and the adrenal gland was therefore removed en bloc with the specimen.

The patient was discharged 3 days post-operatively. His renal function improved, with creatinine decreasing to 89. Histopathology revealed a 95mm intraparenchymal deposit of SCC. It contained both solid and cystic elements and was centred around the renal hilum. The tumour extended to the renal capsule with perinephric extension. A secondary deposit was noted in the periadrenal fat, invading into the adrenal capsule. The renal vein and artery displayed clear margins; however, the hilar soft tissue margin was involved. Ultimately, there was no evidence to suggest a primary tumour of the renal tract. The patient will undergo surveillance CT at 3 months post-operatively, with consideration of commencing further immunotherapy with cemiplimab.

Distant metastasis of lip SCC is rare, with solitary renal metastasis virtually unreported. This case raises awareness that these atypical tumours can exist, and a multidisciplinary team approach is necessary given the lack of pre-existing evidence for decision making. In cases where these rare tumours are suspected, wide resection margins are recommended for oncological safety given their invasive histological appearance.