Stathmin expression in pheochromocytomas, paragangliomas, and in other endocrine tumors

Pheochromocytomas are neuroendocrine tumors confined to the adrenal glands, and malignant pheochromocytomas can spread to various sites including the liver, lung, and bones. Paragangliomas occur in numerous locations in the body, so assessment of metastatic disease is more challenging, as patients with familial syndromes often have multiple, possibly independent paragangliomas. The most reliable criterion for malignancy in pheochromocytomas and paragangliomas is metastatic disease. Because there are few immunohistochemical markers that are useful in the diagnosis of malignancy in pheochromocytomas and paragangliomas before they metastasize, more markers are needed to characterize these tumors. Stathmin is a widely expressed 17-kDa cytoplasmic, microtubule destabilizing and sequestering phosphoprotein that is important in cell motility and cancer cell metastasis. It is upregulated in various malignancies. We examined stathmin expression in tissues from patients with pheochromocytomas (n = 48), malignant pheochromocytomas (n = 28), paragangliomas (n = 42), and malignant paragangliomas (n = 21) by immunohistochemistry using tissue microarrays (TMA) with a polyclonal antibody against stathmin. A series of other endocrine tissues and tumors (n = 70) were also examined for stathmin expression. Stathmin was more highly expressed in pheochromocytomas compared to normal adrenals, a finding confirmed by Western blot. There was higher expression of stathmin by immunohistochemical staining in malignant pheochromocytomas compared to pheochromocytomas without metastasis when analyzed by maximal staining (p = 0.012). Stathmin was present in a wide variety of endocrine tumors and was most highly expressed in rapidly proliferating tumors including anaplastic thyroid carcinomas, Merkel cell carcinomas of the skin and small cell carcinomas of the lung. These results show that stathmin is expressed at higher levels in more rapidly proliferating endocrine tumors. However, it is probably not useful as a stand-alone marker to determine malignancy in pheochromocytomas for individual tumors.