Metastatic breast tumor due to nonfunctional parathyroid carcinoma

Nonfunctional parathyroid carcinoma is a very rare malignant disease; only 25 cases have been reported over the last 85 years. We present a patient with a nonfunctional parathyroid carcinoma metastasis to the breast and a review of the pertinent literature. A 71-year-old woman was seen for a self-discovered mass in her left breast. She had undergone surgery 6 years previously for nonfunctional parathyroid cancer. Mammography and ultrasonography of the breast revealed an oval, circumscribed mass. Fine-needle aspiration findings were suspicious for metastasis of parathyroid carcinoma. Serum calcium and intact parathyroid hormone levels were within normal limits. We performed a partial mammary gland resection that included the tumor. Pathological analysis of the resected tumor disclosed findings consistent with parathyroid carcinoma. The nonsecretory state of the tumor was supported by negative immunoreactivity for parathyroid hormone in the tissue and lack of clinical evidence of hyperparathyroidism. To the best of our knowledge, this is the first reported case of parathyroid carcinoma metastasis to the breast. Breast metastasis of parathyroid carcinoma should be included in the differential diagnosis for a patient with a past history of parathyroid carcinoma.