Pleomorphic adenoma of the submandibular salivary glands with marked ossification

Ossifying pleomorphic adenoma of the parotid gland: a case report and review

Pleomorphic adenoma is the most common parotid gland neoplasm and occasionally arises from the deep lobe of the parotid gland with extension into the parapharyngeal space. However, ossification of pleomorphic adenoma is rare, although chondroid and myxochondroid tissue formation is frequently seen histologically. We report an unusual case of ossifying pleomorphic adenoma arising from the deep lobe of the parotid gland in the parapharyngeal space.

Heterotopic ossification: Review of histologic findings and tissue distribution in a 10-year experience

Heterotopic ossification (HO) within tissues involved by a pathologic process is a well-recognized phenomenon. It is most frequently observed in atherosclerotic plaques, in soft tissue around joints, and in the central nervous system. Less frequently, carcinomas and some benign neoplasms will undergo heterotopic ossification. We performed a retrospective review of our experience with HO over a 10-year period to determine the frequency and tissue site distribution of heterotopic ossification. A computerized review of surgical pathology records of approximately 126,000 reports revealed 85 cases in which heterotopic ossification, ectopic bone or metaplastic bone was specifically mentioned in the surgical pathology diagnosis. Twenty-two cases were neoplasms of non-osseous tissues, and 63 cases were non-neoplastic lesions. Immunohistochemical staining for bone morphogenic proteins (BMP) 1, 4, and 6 was performed. Fourteen cases showed staining for BMP-1, 22 cases showed staining for BMP-4, and five cases showed weak staining for BMP-6. HO is a relatively infrequent finding and is more commonly seen in degenerative and reparative conditions than in neoplasms.

Vascular endothelial growth factor in salivary pleomorphic adenomas: one of the reasons for their poorly vascularized stroma

To better understand the poorly vascularized background of the stroma of pleomorphic adenomas, we attempted to determine the expression of molecules related to blood vessels and hypoxic conditions in pleomorphic adenoma. Surgical specimens and tumor cells in primary culture of salivary pleomorphic adenomas were used for immunohistochemistry for CD31, vascular endothelial growth factor (VEGF) and its receptors Flk-1 and Flt-1, as well as for hypoxia markers, such as hypoxia-inducible factor-1alpha (HIF-1alpha) and lactate dehydrogenase-1 (LDH). At the same time, alternative splicing modes of the VEGF gene and expression levels of the HIF-1alpha gene were analyzed in surgical specimens by means of reverse-transcription polymerase chain reaction (RT-PCR) and direct sequencing of the PCR products. In addition to co-immunolocalization with CD31+ vascular endothelial cells, VEGF and its receptors were demonstrated in normal duct epithelial and myoepithelial cells as well as in tumor cells in ductal structures and in myxochondroid stromata. Immunolocalizations for HIF-1alpha and LDH were confirmed in the VEGF-positive area. Immunofluorescence signals for VEGF and others were confirmed in pleomorphic adenoma cells in culture. RT-PCR results showed that there were at least four splicing modes of the VEGF gene, among which VEGF(121) was most enhanced, and higher HIF-1alpha levels in pleomorphic adenomas. The results suggest that pleomorphic adenoma cells produce VEGF in several functional forms for their own proliferation or differentiation, and that the VEGF expression is controlled by hypoxic circumstances of poorly vascularized pleomorphic adenomas.