Humoral hypercalcemia of malignancy: some enigmas on the clinical features

Hypercalcemia related to cholangiocellular carcinoma

Patients with malignancies may develop hypercalcemia due to bone metastases or paraneoplastic reasons. Hepatocellular cancer should be considered in liver masses detected in chronic viral hepatitis B patients with delta agents. However, in our case, we detected cholangiocellular carcinoma in the etiology of hypercalcemia.

Severe hypercalcemia as a harbinger of acute lymphoblastic leukemia

CASE

An 8-year-old girl presented to the emergency department with a history of nausea, vomiting, abdominal pain, tiredness, and weight loss of 18 lb over 3 weeks. The only significant examination finding was moderate dehydration. She was found to have severe hypercalcemia (serum calcium, 20 mg/dL). The complete blood count was normal. She was treated successfully for hypercalcemia with hyperhydration, furosemide, calcitonin, and pamidronate. A few days later, she developed pancytopenia when her bone marrow biopsy specimen established the diagnosis of acute lymphoblastic leukemia.

CONCLUSIONS

Hypercalcemia presents with nonspecific symptoms of nausea, vomiting, pain in the abdomen, constipation, and tiredness. It can be a harbinger of acute lymphoblastic leukemia. Normal complete blood cell count at presentation does not exclude the diagnosis of leukemia.

Increased expression of 25-hydroxyvitamin D-1alpha-hydroxylase in dysgerminomas: a novel form of humoral hypercalcemia of malignancy

Humoral hypercalcemia of malignancy (HHM) is a common paraneoplastic disorder usually associated with increased synthesis of parathyroid hormone-related peptide (PTHrP). Unlike non-cancer forms of hypercalcemia, HHM does not routinely involve increased circulating levels of the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Dysgerminomas are a notable exception to this rule, previous reports having described hypercalcemia with elevated serum 1,25(OH)2D3. To investigate the etiology of this form of HHM we have characterized expression and activity of the enzyme that catalyzes synthesis of 1,25(OH)2D3, 25-hydroxyvitamin D-1alpha-hydroxylase (1alpha-hydroxylase), in a collection of 12 dysgerminomas. RT-PCR analyses indicated that mRNA for 1alpha-hydroxylase was increased 222-fold in dysgerminomas compared to non-tumor ovarian tissue. Parallel enzyme assays in tissue homogenates showed that dysgerminomas produced fivefold higher levels of 1,25(OH)2D3 compared to normal ovarian tissue. Immunolocalization studies indicated that 1alpha-hydroxylase was expressed by both tumor cells and by macrophages within the inflammatory cell infiltrate associated with dysgerminomas. The immunological nature of the increased 1,25(OH)2D3 production observed in dysgerminomas was further emphasized by correlation between expression of 1alpha-hydroxylase and the endotoxin recognition factors CD14 and toll-like receptor 4 (TLR4). These data suggest that inflammatory mechanisms associated with dysgerminomas are the underlying cause of the increased expression and activity of 1alpha-hydroxylase associated with these tumors. We further postulate that this autocrine/paracrine action of 1alpha-hydroxylase may lead to increased circulating levels of 1,25(OH)2D3 and a form of HHM which is distinct from that seen with PTHrP-secreting tumors.

Parathyroid hormone-related peptide producing cholangiocellular carcinoma with a marked psammoma formation

Humoral hypercalcemia caused by parathyroid hormone-related peptide (PTHrP), associated with cholangiocellular carcinoma (CCC), has rarely been documented. There have been no reports of CCC associated with extensive calcification of the tumor with psammoma body formation. A 66-year-old man was admitted with a large calcified tumor in the liver detected on an abdominal X-ray. An ultrasound-guided fine needle biopsy specimen of the liver tumor showed evidence of adenocarcinoma. He had hypercalcemia with an elevated PTHrP level. The patient died because of disseminated intravascular coagulation and progressive hepatic failure. A postmortem examination revealed a large poorly differentiated CCC in the liver. Immunohistochemical examination showed the presence of PTHrP-positive tumor cells. The calcified lesion consisted of a number of accumulated psammoma bodies. We present a case of PTHrP producing CCC with a marked psammoma formation.

Parathyroid hormone-related peptide and bone: pathological and physiological aspects

Parathyroid hormone-related peptide (PTHrP) was initially discovered as a tumor-derived systemic factor which causes humoral hypercalcemia of malignancy. When overproduced and secreted by tumor cells, PTHrP acts on target organs such as bone and kidney to cause hypercalcemia through its 'PTH-like effects'. The hypercalcemic effects of PTHrP are attributed to its N-terminal portion (1-36) which shows a limited homology with PTH and is able to bind to the common PTH/PTHrP receptor. In contrast to such pathological effects as a humoral factor, PTHrP is now recognized as a locally active cytokine produced by a variety of tissues and cell types. Gene knockout experiments have revealed critical roles for PTHrP in a wide spectrum of physiological processes including chondrogenesis. It also significantly contributes to various pathological processes such as tumor metastasis to bone and bone destruction in arthropathies, acting as a bone-resorbing cytokine. Consistent with its divergent roles, regulation of PTHrP expression as well as its mode of action seems to be much more complex than its hormonal counterpart, PTH. In this article, we will briefly review the recent progress in our understanding of both physiological and pathological aspects of PTHrP biology, with a particular focus on its roles as a bone cytokine.

Hypercalcemia: mechanisms, differential diagnosis, and remedies

The urgency for treatment of hypercalcemia is assessed by determining the severity of symptoms and complications and the degree of elevation of serum calcium. Increased bone resorption is the most common pathophysiologic mechanism for hypercalcemia, and several agents are used to inhibit this resorption, including calcitonin and bisphosphonates. However, inhibition of bone resorption controls hypercalcemia for only a limited time, and prompt definitive treatment of the underlying cause, such as primary hyperparathyroidism or malignancy, is essential.