Humoral hypercalcemia in patients with colorectal carcinoma: report of two cases and review of the literature.

ABSTRACT

BACKGROUND: Humoral hypercalcemia rarely is associated with colorectal carcinoma; to the authors' knowledge only nine cases have been reported to date. METHODS: Two cases of advanced colorectal carcinoma with humoral hypercalcemia of malignancy (HHM) are presented. RESULTS: The two patients had severe hypercalcemia without bone metastases. The diagnosis of HHM was based on findings of hypercalcemia, hypophosphoremia, elevated serum parathyroid hormone-related peptide (PTHrP), and positive tumor immunoreactivity to monoclonal PTHrP antiserum. One patient had a colonic adenocarcinoma with a neuroendocrine component and the other patient had rectal adenocarcinoma. Immunoreactive PTHrP was found in both tumor components. Bisphosphonate treatment normalized the hypercalcemia within a few days but it recurred in the patients 2 weeks and 3 weeks later, respectively. The prognosis was extremely poor. CONCLUSIONS: To the authors' knowledge the two cases presented in the current study are the first to be reported with HHM-associated colorectal carcinoma with positive tumor immunoreactivity to PTHrP monoclonal antiserum.