Hypercalcaemia in a patient with fatal adenosquamous carcinoma of the colon.

OBJECTIVE

To report a rare manifestation of metastatic adenosquamous carcinoma of the colon in a patient presenting with humoral hypercalcaemia of malignancy mediated by parathyroid hormone related peptide (PTHrP).

CLINICAL FEATURES

A 58-year-old man with metastatic adenosquamous carcinoma of the colon presented with hypercalcaemia. A technetium bone scan excluded osteolytic bone secondaries. A negative parathyroid subtraction scan and a low serum immunoreactive parathyroid hormone level (1-34 [amino acid fragment]) made the diagnosis of primary hyperparathyroidism unlikely. The diagnosis of humoral hypercalcaemia of malignancy was considered on the basis of an elevated serum PTHrP level and positive tumour immunoreactivity to PTHrP antiserum.

INTERVENTION AND OUTCOME

The hypercalcaemia was effectively treated on two occasions with intravenous administration of aminohydroxy propilidene diphosphonate. Despite interventional chemotherapy, the patient died of progressive carcinomatosis.

CONCLUSION

Hypercalcaemia is an extremely rare occurrence in carcinoma of the colon. This is the first documented case of humoral hypercalcaemia of malignancy associated with adenosquamous carcinoma of the colon mediated by PTHrP.