Invasive-ectopic pituitary adenoma

Many of the tumors of the nasal cavity and paranasal sinuses fall under the category of round cell neoplasms. Among these are olfactory neuroblastoma, sinonasal undifferentiated carcinoma, malignant melanoma, neuroendocrine carcinoma-small cell neuroendocrine carcinoma, malignant lymphoma, extramedullary plasmacytoma, invasive-ectopic pituitary adenoma, rhabdomyosarcoma, and Ewing s sarcoma (ES)-peripheral neuroectodermal tumor (ES/ PNET). But there is also a host of other epithelial lesions that are unique to the sinonasal tract. 

TABLE 9.8 Differential Diagnosis of Invasive-Ectopic Pituitary Adenoma ... 

Pituitary adenomas presenting in the nasal cavity, paranasal sinuses, and nasopharynx are distinctly unusual and can be divided into two types invasive and ectopic.Invasive sinonasal pituitary adenomas are secondary to downward proliferation of a primary sellar tumor. This event occurs in about 2% of all sellar tumors.Ectopic adenomas are those that arise from aberrant embryogenesis of the pituitary gland. 

Pituitary lesions can present in the sinonasal tract, either as invasive adenomas or as ectopic tumors. 

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