PARATHYROID CARCINOMA

Parathyroid carcinoma occurs equally in men and women, in contrast to benign PHPT, wich affects mostly women with male-to-female ratio of 1:3. Most patients with PC present in their fifth decade of life.^1,2 In the present series, the male-to-female ratio was 2:1, with not same decade of their life.

Although PC has been associated with certain clinical risk factors, such as familial hyperparathyroidism, history of neck irradiation, and end-stage renal disease, its etiology remains unclear. Most of these tumor are functioning, and their clinical presentation is that of severe hypercalcemia, with serum calcium level usually 3 to 4 mg/dL above the upper normal limit and PTH levels 3 to 10 times above normal. In the patients of this series, serum calcium levels is not increase to high, and PTH levels in 3 of them exceeded normal limits just more than 2-fold. More than 50% of patients with PC present with renal functional abnormalities.⁸

The en bloc resection of the tumor, together with the ipsilateral thyroid lobe and adjacent structures, when involved, avoiding any capsular rupture of the lesion, provides the best prognosis for the patient.^1,9 For this reason, the high index of preoperative suspicion and the intra operative recognition of the malignant potential are of fundamental importance. At the time of the initial operation, extensive local or distant disease is uncommon. The recurrent laryngeal nerve can be sacrificed only in the case of locally aggressive tumor.⁹ Prophylactic or radical neck dissection does not improve survival, and it is associated with an increased risk of operative complications.^{2, 9}

Recurrent hypercalcemia implies relapse of PC. Recurrent or metastatic PC is primarily treated surgically. Thorough physical examination and imaging investigation are obligatory for an efficient preoperative planning. Recurrence in the neck should be treated with wide excision, including the regional lymph nodes. ^2,8 Resection of localized pulmonary and liver metastases, when this is technically possible, is also indicated. The aims of surgery are to reduce the tumor load and to provide effective time interval of normocalcemia.⁶ Although PC has been traditionally considered as a radioresistant tumor, recent retrospective studies suggested that adjuvant radiotherapy may produce a positive benefit on survival.^9,10 Chemotherapy with various regimens has been used but without proven efficacy.

References

1.        Koea JB, Shaw JH. Parathyroid cancer: biology and management. Surg Oncol 1999;8:155-65.

2.        Hundahl SA, Fleming ID, Fremgen AM, et al. Two hundred eighty-six cases of parathyroid carcinoma treated in the US between 1985–1995:a National Cancer Data Base Report. The American College of Surgeons Commission on Cancer and the American Cancer Society.Cancer 1999;86:538-44.

3.        Lee PK, Jarosek SL, Virnig BA, Evasovich M, Tuttle TM. Trends in the incidence and treatment of parathyroid cancer in the United States. Cancer 2007;109: 1736e41.

4.        Wei CH, Harari A. Parathyroid carcinoma: update and guidelines for management. Curr Treat Options Oncol 2012;13:11e23.

5.        Thompson SD, Prichard AJ. The management of parathyroid carcinoma. Curr Opin Otolaryngol Head Neck Surg 2004;12:93e7.

6.        Shane E. Clinical review 122: parathyroid carcinoma. J Clin Endocrinol Metab 2001;86:485e93.

7.        Lee PK, Jarosek SL, Virnig BA, Evasovich M, Tuttle TM. Trends in the incidence and treatment of parathyroid cancer in the United States. Cancer 2007;109: 1736e41.

8.        Wynne AG, van Heerden J, Carney JA, et al. Parathyroid carcinoma: clinical and pathologic features in 43 patients. Medicine (Baltimore) 1992;71:197-205.

9.        Clayman GL, Gonzalez HE, El-Naggar A, et al. Parathyroid carcinoma: evaluation and interdisciplinary management. Cancer 2004;100:900-5.

10.    Kirkby-Bott J, Lewis P, Harmer CL, et al. One stage treatment of parathyroid cancer. Eur J Surg Oncol 2005;31:78-83