The initial manifestations of parathyroid carcinoma are quite similar to those of the two leading causes of primary hyperparathyroidism: nonmalignant parathyroid hyperplasia and parathyroid adenoma. The intensity of the symptoms and manifestations tends to be greater for parathyroid carcinoma than benign lesions, as is the rapidity of onset. Patients with parathyroid carcinoma present more commonly with hypercalcemic crisis and significantly higher levels of hypercalcemia than patients with nonmalignant causes of hyperparathyroidism. The levels of circulating parathyroid hormone are also significantly higher in parathyroid carcinoma. The signs and symptoms of parathyroid carcinoma are therefore an exaggeration of those of primary hyperparathyroidism owing to benign disease. They are well summarized by the mnemonic "stones, bones, groans, psychic moans and fatigue overtones," referring to the effect of hyperparathyroidism-induced hypercalcemia on target organs.
Stones refer to hypercalcemia-induced nephrolithiasis, seen in 30 to 60% of cases of primary hyperparathyroidism. In parathyroid carcinoma, it is not uncommon to see both nephrolithiasis (kidney stones) and nephrocalcinosis (precipitation of calcium phosphate in the renal tubules). Untreated and unmanaged, both complications may lead to irreversible azotemia and renal failure. One recent study revealed a prevalence of renal insufficiency of 84% in parathyroid carcinoma.8 In addition, hypercalcemia leads to an obligatory calciuria with large-volume polyuria that can result in significant intravascular volume depletion, further contributing to the underlying azotemia.
Bones refer to the skeletal manifestations of hypercalcemia, which range from myalgias and arthralgias to osteopenia and severe osteoporosis, seen in 40 to 70% of cases of persistent hyperparathyroidism. The radiographic manifestations of prolonged hyperparathyroidism, subperiosteal bone resorption (Figure 7-1), "salt and pepper" skull, dif-
fuse spinal osteopenia, or osteitis fibrosis cystica (abnormal calcium deposits in soft tissue or muscles), are seen in 41 to 91% of patients with parathyroid carcinoma, compared with 5% of benign hyperparathyroidism.911 The concurrent development of skeletal and renal manifestations of hypercalcemia is also seen much more commonly in the presentation of parathyroid carcinoma than in benign hyper-parathyroidism. It is a distinguishing feature of the higher level of hypercalcemia and hyperparathy-roidism associated with parathyroid carcinoma.
Groans refer to the gastrointestinal manifestations of hypercalcemia, seen in 15% of primary hyper-parathyroidism. Patients can present with anorexia, constipation, weight loss, nausea and vomiting, and, peptic ulcer disease. Up to 10% of patients with parathyroid carcinoma can present with acute pancreatitis or recurrent severe pancreatitis. Unfortunately, the degree of anorexia, decreased fluid intake, and vomiting seen with untreated parathyroid carcinoma only aggravates the underlying intravascular depletion caused by hyperparathyroid-induced hypercalcemia.
Finally, psychic moans and fatigue overtones refer to the psychological and general systemic manifestations of uncontrolled hypercalcemia, seen commonly in primary hyperparathyroidism. These symptoms range from depression and fatigue to mild confusion, muscle weakness, and profound coma. The severity of the confusion or coma correlates with the degree and duration of hypercalcemia. Rapid treatment and correction of the hypercalcemia, which will reverse the alteration in sensorium associated with hypercalcemia, should be initiated rapidly. The first step is to replenish the depleted intravascular volume with aggressive intravenous normal saline, typically at rates of 300 cc/hour for 24 or more hours. Only when intravascular volume is restored can the use of calciuric diuretics, such as furosemide (at a starting dose of 20 to 40 mg intravenously or orally), begin in earnest. If attempts at diuresis are initiated prior to replenishing intravascular volume, one runs the risk of exacerbating the renal dysfunction and underlying azotemia present in hypercalcemia.
Approximately 50% of patients with parathyroid carcinoma present with a palpable neck mass, in contrast to patients with primary hyperparathyroidism in whom the parathyroid tumor is palpable in 4%.12 The parathyroid cancers tend to be firm and may be fixed to the underlying structures; they are usually painless. In a few patients with direct invasion of underlying structures, there can be pain; there can also be hoarseness owing to invasion of the recurrent laryn-geal nerve. Most patients with parathyroid carcinoma will have a neck mass of 3 cm. At surgery, the mass will often appear as a gray-white firm mass (Figure 7-2). In contrast, adenomas and hyperplastic parathyroid glands tend to be reddish brown or chestnut (Figure 7-3).
The laboratory abnormalities in patients with parathyroid carcinoma are those of primary hyper-parathyroidism. The level of hypercalcemia tends to be higher than for other nonmalignant causes of primary hyperparathyroidism, on the order of 14 to 15 mg/dL. The level of parathyroid hormone is usually also much more elevated in patients with parathyroid carcinoma than in patients with hyper-plasia or adenoma (Table 7-1), usually 3 to 10 times the upper limit of normal. Alkaline phosphatase and a and P subunits of human chorionic gonadotropin may also be elevated in parathyroid carcinoma.
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