As with other tumors of the central nervous system (CNS), no tumor, nodes, metastases-based American Joint Committee on Cancer classification and staging system for pituitary tumors exists.[1] Pituitary tumors are classified according to size and divided into microadenomas (i.e., the greatest diameter is <10 mm) and macroadenomas (i.e., the greatest diameter is =I0 mm).[2] Most pituitary adenomas are microadenomas. The most widely used radioanatomical classification was based primarily on a neuroradiological examination including skull x-rays, pneumoencephalography, polytomography, and carotid angiography.[3] Subsequently validated by the application of more accurate magnetic resonance imaging (MRI) and computed tomography, this radioanatomical classification places adenomas into 1 of 4 grades (I-IV) and has been augmented by additional studies including immunohistochemistry and electron microscopy.[4] Currently, MRI is considered the imaging modality of choice for the diagnosis of pituitary disorders because of its multiplanar capability and good soft tissue contrast enhancement.[2] Because no unequivocal histopathologic features of pituitary carcinoma exist, the diagnosis of malignancy is reserved for pituitary neoplasms that have metastasized to remote areas of the CNS or to outside of the CNS.[5,6,7]

The radiographical classification for pituitary adenomas is as follows:[3,8]

• 0: Normal pituitary appearance.
• I: Enclosed within the sella turcica, microadenoma, smaller than 10 mm.
• II: Enclosed within the sella turcica, macroadenoma, 10 mm or larger .
• III: Invasive, locally, into the sella.
• IV: Invasive, diffusely, into the sella.

The grading schema for suprasellar extensions is as follows:[3,8]

1. 0 to 10 mm suprasellar extension occupying the suprasellar cistern.
2. 10 mm to 20 mm extension and elevation of the third ventricle.
3. 20 mm to 30 mm extension occupying the anterior of the third ventricle.
4. A larger than 30 mm extension, beyond the foramen of Monro, or Grade C with lateral extensions.

References:

1. Brain and spinal cord. In: American Joint Committee on Cancer.: AJCC Cancer Staging Manual. 6th ed. New York, NY: Springer, 2002, pp 387-90.
2. Ezzat S, Asa SL, Couldwell WT, et al.: The prevalence of pituitary adenomas: a systematic review. Cancer 101 (3): 613-9, 2004.
3. Hardy J: Transsphenoidal surgery of hypersecreting pituitary tumors. In: Kohler PO, Ross GT, eds.: Diagnosis and treatment of pituitary tumors: proceedings of a conference sponsored jointly by the National Institute of Child Health and Human Development and the National Cancer Institute, January 15-17, 1973, Bethesda, Md. Amsterdam, The Netherlands: Excerpta medica, 1973, pp 179-98.
4. Asa SL, Ezzat S: The cytogenesis and pathogenesis of pituitary adenomas. Endocr Rev 19 (6): 798-827, 1998.
5. Scheithauer BW, Kovacs KT, Laws ER Jr, et al.: Pathology of invasive pituitary tumors with special reference to functional classification. J Neurosurg 65 (6): 733-44, 1986.
6. Della Casa S, Corsello SM, Satta MA, et al.: Intracranial and spinal dissemination of an ACTH secreting pituitary neoplasia. Case report and review of the literature. Ann Endocrinol (Paris) 58 (6): 503-9, 1997.
7. Kemink SA, Wesseling P, Pieters GF, et al.: Progression of a Nelson's adenoma to pituitary carcinoma; a case report and review of the literature. J Endocrinol Invest 22 (1): 70-5, 1999.
8. Yeh PJ, Chen JW: Pituitary tumors: surgical and medical management. Surg Oncol 6 (2): 67-92, 1997.