Renal cell carcinoma metastasis to the parathyroid gland: A very rare occurrence

INTRODUCTION: Metastases to the parathyroid gland are very uncommon. Although renal cell carcinoma metastasis to the head and neck region is well recognised, with a predilection for unpredictable metastasis to unusual sites such as the thyroid gland, nose, paranasal sinuses, and cranial bones, there are no reports of parathyroid gland involvement. PRESENTATION OF CASE: We describe an unusual case of renal cell carcinoma metastasis to a parathyroid gland in a 69-year-old male who had been treated 8 years previously for a pT3b N0 M1 clear cell carcinoma of the right kidney with a right nephrectomy, and interferon immunotherapy for 18 months. The patient had originally presented to the plastic surgeons with a rapidly enlarging 3 cm superficial lesion on the ventral aspect of the left forearm, which was excised with histology revealing metastatic renal (clear) cell carcinoma. DISCUSSION: Renal cell carcinoma has a reputation for unpredictable patterns of metastasis, and our case highlights this, with the first description in the literature of parathyroid gland metastasis. Despite the poor prognosis associated with metastatic renal cell carcinoma, our patient is still alive 10 years following original presentation, despite having metastasis to two different extra-renal sites and a shortened course of initial adjuvant systemic therapy. CONCLUSION: In parathyroid gland metastasis, metastectomy can offer excellent local long term local control.