Haemangioma of the parathyroid gland. Does it really exist?

We are reporting a case of a capillary haemangioma-like proliferation arising within a parathyroid gland adenoma, associated with primary hyperparathyroidism. The vessel proliferation bearing a close resemblance to a capillary haemangioma consisted of tightly packed capillaries, endothelial buds and occasional small caliber muscle-containing vessels. The observation expands the spectrum of tumour-associated vascular proliferations by adding an exuberant haemangioma-like pattern to its extreme end. These are a heterogeneous group of lesions reportedly induced by aberrant production of angiogenic factors. We investigated expression of VEGF, pKDR, FGF2, HIF1alpha and HIF2alpha and only VEGF gave a strong positive reaction in the adenoma cells entrapped in the vascular meshwork. Although this does not constitute a proof that aberrant VEGF production was a causative agent, unexpected supportive evidence for its pathogenic role emerged from a failure to detect chromogranin A. Chromogranin A is a precursor of several regulatory proteins, including vasostatin I, a multilevel suppressor of VEGF. The production of vasostatin I may have been reduced in a chromogranin A-negative adenoma which could lead to a loss of its opposing effect on VEGF-regulated processes. The only two other published cases of haemangioma of the parathyroid gland were reported in patients diagnosed with primary parathyroid hyperplasia with hyperparathyroidism, a pathophysiologic condition similar to our case. Therefore we raise the question whether these tumours could also represent a reactive phenomenon.