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Pituitary tumors represent from 10% to 25% of all intracranial neoplasms. Depending on the study cited, pituitary tumors can be classified into three groups according to their biological behavior:[1,2]
Adenomas comprise the largest portion of pituitary neoplasms with an overall estimated prevalence of approximately 17%. Only a minority of adenomas are symptomatic. In addition, pituitary adenomas may be distinguished anatomically as intrapituitary, intrasellar, diffuse, and invasive. Invasive adenomas, which account for approximately 35% of all pituitary neoplasms, may invade the dura mater, cranial bone, or sphenoid sinus. Carcinomas account for 0.1% to 0.2% of all pituitary tumors.[6,7]
The most characteristic-presenting features of pituitary adenomas include inappropriate pituitary hormone secretion and visual field deficits.
Rare signs and symptoms of pituitary disease include:
The signs and symptoms commonly associated with pituitary tumors derived from each specific cell type (i.e., prolactinomas, corticotroph adenomas, somatotroph adenomas, thyrotroph adenomas, and nonfunctioning adenomas) are as follows:
Prolactin-producing pituitary tumors
Signs and symptoms of prolactin (PRL)-producing pituitary tumors, also known as prolactinomas and lactotroph adenomas, may include:
Adrenocorticotrophic hormone-producing pituitary tumors
Signs and symptoms of adrenocorticotrophic hormone (ACTH)-producing pituitary tumors, also known as corticotroph adenomas, may include:
Growth hormone-producing pituitary tumors
Signs and symptoms of growth hormone (GH)-producing pituitary tumors, also known as somatotroph adenomas, may include:
Thyrotropin-producing pituitary tumors
Signs and symptoms of thyrotropin (thyroid-stimulating hormone [TSH])-producing tumors, also known as thyrotroph adenomas, may include:
Signs and symptoms of nonfunctioning adenomas (most commonly gonadotroph adenomas) may include:
In addition to cell-type specific presentations, pituitary apoplexy (i.e., pituitary adenoma apoplexy) represents another important clinical presentation of pituitary adenomas. Pituitary apoplexy can result from an acute hemorrhagic or ischemic infarction of the pituitary in patients harboring often unrecognized secreting or nonfunctioning pituitary adenomas. In a series analyzing 40 cases of pituitary apoplexy, the presenting signs and symptoms included headache (63%), vomiting (50%), visual field defects (61%), ocular paresis (40%), mental deterioration (13%), hyponatremia (13%), and syncope (5%); in only four cases pituitary tumor was diagnosed prior to presentation.
The development of pituitary adenomas may also occur as a component of three familial cancer syndromes:
A number of other lesions should be considered in the differential diagnosis of sellar masses. Although rare, lymphocytic (i.e., autoimmune) hypophysitis should be considered in the differential diagnosis of any nonsecreting pituitary mass, especially when occurring during pregnancy or postpartum. In addition, the clinician should consider craniopharyngioma and Rathke cleft cyst in the differential diagnosis of pituitary tumors. Sellar masses may also result from tumors that are metastatic to the pituitary. This typically occurs as a part of a generalized metastatic spread and is usually associated with five or more additional metastatic sites, especially osseous; breast and lung cancer are the most common primary neoplasms metastasizing to the pituitary.
Pituitary adenomas can be classified according to staining affinities of the cell cytoplasm, size, endocrine activity, histologic characteristics, hormone production and contents, ultrastructural features, granularity of the cell cytoplasm, cellular composition, cytogenesis, and growth pattern. Recent classifications, however, omit criteria based on tinctorial stains (i.e., acidophilic, basophilic, and chromophobic) because of the poor correlation between staining affinities of the cell cytoplasm and other pathological features of pituitary tumors, such as the type of hormone produced and cellular derivation.[1,2]
A unifying pituitary adenoma classification incorporates the histological, immunocytochemical, and electron microscopic studies of the tumor cells, and stresses the importance of hormone production, cellular composition, and cytogenesis. This classification emphasizes the structure-function relationship and attempts to correlate morphologic features with secretory activity.
Pituitary adenomas may be classified based on:
An MRI scan is now considered the imaging modality of choice for the diagnosis of pituitary disorders because of its multiplanar capability and good soft tissue contrast enhancement. Sagittal T1-weighted images, clearly displaying the anterior and posterior lobes and the stalk on the same plane, and coronal images, displaying the relation between the pituitary and cavernous sinuses, are optimal for identifying a pituitary adenoma. A 3-mm thin slice typically is used to obtain optimal resolution. A computed tomography (CT) scan may also be a useful diagnostic tool with coronal scans providing the optimal view; however, CT scans appear to be less sensitive than MRI scans in this application. For each imaging technique, a focal hypointensity within the pituitary gland is considered abnormal and suggestive of an adenoma. An MRI scan is also the best diagnostic imaging choice for pituitary carcinomas; metastases may be found in the cerebral lobes, cerebellum, spinal cord, leptomeninges, and subarachnoid space.
This radioanatomical classification places adenomas into 1 of 4 grades (I-IV). (Refer to the Stage Information For Pituitary Tumors section of this summary for more information.) The grades are as follows:
Using functional criteria, pituitary adenomas can be characterized as:
Hormone-secreting pituitary carcinomas may elicit similar signs and symptoms according to the particular hormone that is secreted; they may also produce signs and symptoms related to malignant spread. Because no unequivocal histopathologic features of carcinoma exist, the diagnosis of malignancy is reserved for pituitary neoplasms that have metastasized to remote areas of the central nervous system (CNS) or outside of the CNS.[12,13,14] In a review of 95 cases of pituitary carcinoma, 68% of the cases were found to be hormone-producing and PRL (26%) and ACTH (25%) were the most common hormonal subtypes. Pituitary carcinomas producing GH were the second most common of the hormonal subtypes, and FSH/LH-producing and TSH-producing carcinomas were even more rarely reported. Other reports indicate that as many as 88% of pituitary carcinomas are endocrinologically active, and ACTH-secreting tumors are the most common. Although only 2% to 10% of pituitary adenomas are ACTH-secreting, the percentage of pituitary carcinomas that secrete ACTH is estimated to be much higher at 25% to 34%.[15,16,17,18,19] In a series of 15 cases, carcinomas showed a greater tendency toward systemic metastasis than craniospinal metastasis; the rate of systemic metastasis was 71% for PRL-producing cell tumors and 57% for ACTH-producing tumors.
Prolactin (PRL)-Producing Pituitary Tumors
PRL-producing pituitary tumors, also known as prolactinomas and lactotroph adenomas, secrete PRL and are typically an intrasellar tumor. In women, these adenomas are often small (<10 mm). In either sex, however, they can become large enough to enlarge the sella turcica. These adenomas represent the most common hormone-producing pituitary tumors and account for 25% to 41% of tumor specimens.
Adrenocorticotrophic Hormone (ACTH)-Producing Pituitary Tumors
The major manifestation of ACTH-producing pituitary tumors, also know as corticotroph adenomas, is secretion of adrenocorticotropic hormone (ACTH), which results in Cushing syndrome. These tumors are initially confined to the sella turcica, but they may enlarge and become invasive after bilateral adrenalectomy (i.e., Nelson syndrome). These adenomas represent the second or third most common hormone-producing pituitary tumors, depending on the series; in one series, these tumors accounted for 10% of all tumor specimens.[1,3]
Growth Hormone (GH)-Producing Pituitary Tumors
GH-producing pituitary tumors, also known as somatotroph adenomas, produce GH, resulting in gigantism in younger patients and acromegaly in others. Suprasellar extension is not uncommon. These adenomas represent the second or third most common hormone-producing pituitary tumors, depending on the series; in one series these adenomas accounted for 13% of tumor specimens.[1,3]
Thyrotropin-Producing Pituitary Tumors
Thyrotroph-producing pituitary tumors, also known as thyrotroph adenomas, secrete thyroid-stimulating hormone (TSH), also known as thyrotropin, which results in hyperthyroidism without TSH suppression. Many are large and invasive, may be plurihormonal, and secrete both GH and/or PRL. These tumors are rare and account for no more than 2% of tumor specimens.[1,3,20]
Gonadotroph (FSH-Producing and/or LH-Producing) Adenomas
Gonadotroph adenomas may secrete FSH and/or LH, or the alpha or beta subunits that comprise these heterodimers, which, depending on gender, may result in ovarian overstimulation, increased testosterone levels, testicular enlargement, and pituitary insufficiency caused by compression of the pituitary stalk or destruction of normal pituitary tissue by tumor. Many gonadotroph tumors, however, are unassociated with clinical or biochemical evidence of hormone excess and may be considered to be nonfunctioning or endocrine-inactive tumors. Functional, clinically detectable gonadotroph adenomas are rare.
Plurihormonal tumors produce more than one hormone. Morphologically, they can be either monomorphous or plurimorphous. Monomorphous plurihormonal adenomas consist of one cell population that produces two or more hormones. The adenoma cells often differ from nontumorous adenohypophysial cells, and their cellular derivation may remain obscure despite extensive morphological studies. Plurimorphous plurihormonal adenomas consist of two or more distinct cell types, and each produces one hormone. Thyrotroph adenomas are often plurihormonal.
Nonfunctioning (Endocrine-Inactive) Adenomas
These tumors arise from the adenohypophysis and cause symptoms when they extend beyond the sella, which results in pressure on the surrounding structures rather than secretion of a hormonally active substance. Endocrine-inactive adenomas show positive immunostaining for one or more pituitary hormones; however, they are not associated with clinical and biochemical evidence of hormone excess. Gonadotrophic hormones, as detected by antisera to beta-FSH and beta-LH, are present in many clinically nonfunctioning adenomas. Some of these adenomas are recognized by electron microscopy to have gonadotrophic differentiation, but some have characteristics of less well-differentiated cells and resemble the null cells that were initially thought to be undifferentiated precursors of adenohypophysial cells. Endocrine-inactive pituitary adenomas comprise approximately 30% to 35% of the pituitary tumors in most series and are the most common type of macroadenoma.
Oncocytic tumors of the pituitary, also known as pituitary oncocytomas, are characterized by an abundance of mitochondria, which may fill up to 50% of the cytoplasmic area, which is normally around 8%, and obscure other organelles. These tumors are usually unassociated with clinical and biochemical evidence of hormone excess; in some cases, they may be accompanied by various degrees of hypopituitarism and/or mild hyperprolactinemia. Oncocytic change may occur in several other pituitary tumor types.
Pituitary carcinomas are usually endocrinologically functional, and ACTH-producing and PRL-producing tumors are the most frequent.[2,8] The histological and cytological characteristics of pituitary carcinomas vary from bland and monotonous to frankly malignant. Carcinomas show a variable degree of nuclear atypia and cellular pleomorphism, but they also show significantly higher mitotic rates and cell proliferation indices than adenomas. Carcinomas account for 0.1% to 0.2% of all pituitary tumors.[8,16]
Breast and lung cancer are the most common primary neoplasms metastasizing to the pituitary. Although tumors that are metastatic to the pituitary have been reported to be as high as 28% in autopsy series, the majority of metastatic tumors are clinically silent.
Other tumors that arise in the pituitary include craniopharyngiomas, meningiomas, and germ cell tumors; the rare granular cell tumors, pituicytomas, and gangliogliomas; and the even rarer gangliocytomas, lymphomas, astrocytomas, and ependymomas.
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. 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). 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. 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.
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. 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]
The grading schema for suprasellar extensions is as follows:[3,8]
The goals of treatment of pituitary adenomas include normalization of hormonal secretion (i.e., normalization of hypersecretion and improvement in hypofunction) and resolution or cessation of the progression of neurological defects.
Standard treatments for patients with pituitary tumors include:
The treatment of choice must be individualized and is dictated by the type of tumor, the nature of the excessive hormonal expression, and whether or not the tumor extends into the brain around the pituitary.[1,2]
The transsphenoidal microsurgical approach to a pituitary lesion is the most widely employed surgical approach to pituitary lesions and represents a major development in the safe surgical treatment of both hormonally active and nonfunctioning tumors.[3,4,5] This approach is often successful in debulking tumors, even those that have a significant suprasellar extension.
A contraindication to this approach includes tumors with a significant suprasellar extension with an hourglass-shaped narrowing between the intrasellar and suprasellar component because blind attempts to reach the suprasellar tumor may lead to cerebral damage. In addition, an infection in the sphenoid sinus is potentially a contraindication to the transsphenoidal approach. In such cases, craniotomies via a pterional or subfrontal approach may be performed. Rapid deterioration of vision is an immediate indication for surgery to relieve pressure produced by an expanding tumor mass, except in the case of macroprolactinomas (where intensive observation with a patient on dopaminergic agonists may be an acceptable alternative). Progressive deterioration of visual fields is often the primary neurological criterion on which surgical management decisions are based.
Conventional radiation therapy is an effective adjunct to the treatment of pituitary tumors. The advantages of radiation therapy are that it is noninvasive and suitable for surgically high-risk patients. The clinical and biochemical response, however, is slow and may require from 2 years to 10 years for complete and sustained remission. In addition, radiation therapy carries a substantial risk of hypopituitarism (i.e., approximately 30% at 10 years).
Hormone-secreting tumors may be treated with surgery or radiation therapy. Surgical therapy is the treatment of choice for growth hormone-(GH) producing, adrenocorticotropic hormone-(ACTH) producing, and endocrine-inactive adenomas. GH-secreting tumors can be treated with somatostatin analogues, dopamine analogues, and the newer GH-receptor antagonists, such as pegvisomant. Ketoconazole, an inhibitor of steroidogenesis, is considered the first drug of choice as adjunctive medical therapy for ACTH-producing tumors. Somatostatin analogues are the drugs of choice for treatment of thyroid-stimulating, hormone-producing adenomas; however, the efficacy of treatment may wane with time.
The natural history of growth hormone-secreting and ACTH-secreting pituitary tumors is usually one of slowly progressive enlargement. Microprolactinomas, however, often remain unchanged, or decrease in size over time, and have been observed to undergo complete, spontaneous resolution on occasion.
Treatments under clinical evaluation for patients with pituitary tumors include:
Standard Treatment Options for Prolactin (PRL)-Producing Pituitary Tumors
Standard treatment options for PRL-producing pituitary tumors include the following:
When the pituitary tumor secretes PRL, treatment will depend on tumor size and the symptoms that result from excessive hormone production. Patients with PRL-secreting tumors are treated with surgery and radiation therapy.
Most microprolactinomas and macroprolactinomas respond well to medical therapy with ergot-derived dopamine agonists, including bromocriptine and cabergoline. For many patients, cabergoline has a more satisfactory side effect profile than bromocriptine. Cabergoline therapy may be successful in treating patients whose prolactinomas are resistant to bromocriptine or who cannot tolerate bromocriptine, and this treatment has a success rate of more than 90% in patients with newly diagnosed prolactinomas.[3,4,5] In a prospective study, cabergoline was safely withdrawn in patients with normalized prolactin levels and no evidence of tumor, which may effect a cure rate of approximately 70%. On the basis of its safety record in pregnancy, however, bromocriptine is the treatment of choice when restoration of fertility is the patient's goal.
Microprolactinomas change little in size with treatment, but macroprolactinomas can be expected to shrink, sometimes quite dramatically. Microprolactinomas may decrease in size over time and have been observed to undergo complete, spontaneous resolution on occasion. Surgery is typically reserved for those patients who cannot tolerate dopamine agonists, who suffer pituitary apoplexy during treatment, or whose macroprolactinomas are not responsive to medical therapy. Occasionally, these tumors may ultimately require radiation therapy.
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Standard Treatment Options for Adrenocorticotropic Hormone (ACTH)-Producing Pituitary Tumors
Standard treatment options for ACTH-producing pituitary tumors include the following:
For patients with corticotroph adenomas, transsphenoidal microsurgery is the treatment of choice.[1,2] Remission rates reported in most series are approximately 70% to 90%. In a series of 216 patients, who were operated on using a transsphenoidal approach, 75% experienced long-term remission, 21% experienced persistence of Cushing disease, and 9% had recurrence after the initial correction of the hypercortisolism. The average time interval for reoperation was 3.8 years. Seventy-nine percent of the tumors were microadenomas, and 18% were macroadenomas; 86% of the cases with microadenoma had long-term remission, whereas, only 46% of those with macroadenoma had remission. In cases in which hypercortisolemia persists, early repeat exploration and/or radiation therapy or laparoscopic bilateral adrenalectomy may be required.
Radiation therapy has been used in patients who are deemed to be poor surgical candidates and has also been used as adjunctive therapy in patients with residual or recurrent active tumor.[1,4]
Drug therapy is considered to be an adjunct to transsphenoidal microsurgery in cases in which there is a residual tumor and in cases in which one is awaiting the effects of the radiation therapy. Steroidogenesis inhibitors, including mitotane, metyrapone, ketoconazole, and aminoglutethimide are used. Ketoconazole is the best tolerated of these agents and is effective as monotherapy in about 70% of patients.
If untreated, patients frequently succumb to cardiovascular disease or infection.
Treatment Options Under Clinical Evaluation for ACTH-Producing Pituitary Tumors
Treatment options under clinical evaluation for ACTH-producing pituitary tumors include the following:
Standard Treatment Options for Growth Hormone (GH)-Producing Pituitary Tumors
Standard treatment options for GH-producing pituitary tumors include the following:
Treatment for patients with acromegaly includes surgical, radiation, and medical therapies. Treatment will depend on the size and extent of the tumor and the need for rapid cessation of hormone function that results in serious clinical sequelae (i.e., hypertension and cardiomyopathy).
Microadenomectomy or macroadenoma decompression is approached transsphenoidally in most patients. Increasingly, endoscopic surgery is used to allow the entire surgical field to be viewed and to allow tumor tissue that would otherwise be inaccessible with rigid instruments to be safely resected. Complete return of GH concentrations to normal, however, is not often achieved. Increasingly, adjunctive radiation therapy is reserved for tumors that extend beyond the safe operative area and appear to pose an ongoing threat.
Drug treatment, whether used as an adjuvant or primary therapy in appropriately selected patients, which is advocated by some, includes the use of somatostatin analogues, such as octreotide; dopamine analogues, such as bromocriptine; and, the GH-receptor antagonist, pegvisomant. As the first of a new class of GH-receptor antagonists, pegvisomant works by inhibiting functional dimerization of GH receptors and thereby inhibits GH action. Preliminary results indicate that it may be the most effective medical treatment for acromegaly reported to date.[1,2]
In acromegalic patients, impaired glucose tolerance, hypertension, and hyperlipidemia should be vigorously treated concurrently with definitive therapy. A multidisciplinary clinical approach may be required for the treatment of arthritis, carpal tunnel syndrome, obstructive sleep apnea, and prognathism. Mortality is related primarily to cardiovascular and respiratory diseases.
Standard Treatment Options for Thyrotropin-Producing Tumors
Standard treatment options for thyrotropin-producing tumors include the following:
Transsphenoidal surgery is the treatment of choice for patients with thyrotropic adenomas. Adjuvant radiation therapy may be employed when surgery is known to be noncurative even if the patient is still euthyroid because relapse is inevitable, and the full effect of radiation therapy requires months or years.
Medical therapy may be required for patients who still have hyperthyroid symptoms despite surgery and external radiation. Somatostatin analogues are the drugs of choice for treatment; however, the efficacy of treatment may wane with time.[1,2,3,4]
Standard Treatment Options for Nonfunctioning Pituitary Tumors
Standard treatment options for nonfunctioning pituitary tumors include the following:
The selection of treatment for patients with nonfunctioning (endocrine-inactive) tumors will depend on tumor size, the progressive course of the disease, and anatomical structures affected by the tumor extension. The majority of patients present with suprasellar extension and visual field deficits. In addition, many have hormone deficits prior to treatment. The initial treatment of patients with gonadotroph adenomas is usually by transsphenoidal surgery, particularly if the adenoma presents with neurological symptoms, because the effect of radiation therapy occurs too slowly, and no reliable medical therapy exists.
Surgical management is typically considered the first choice of treatment for patients with endocrine inactive pituitary adenomas because of its effectiveness in ameliorating symptoms of chiasmal compression and headache. Radical removal of the tumor, however, is difficult to obtain because of the frequent invasiveness into the cavernous sinus. Seventy percent to 80% of patients experience normalization or improvement of visual field defects, and almost 100% of patients with headache as a presenting symptom experience relief. Regrowth of the tumor after radiologically confirmed gross total removal appears to be uncommon. In a series of 32 patients, only 2 (6.2%) with gross total tumor removal and no postoperative radiation therapy showed radiological recurrence of the tumor at a mean follow-up of 5.5 years.
Radiation therapy has been administered routinely in the postoperative period and after clear radiological evidence of residual or recurrent tumor has been demonstrated.[1,2,3] Drug therapy appears to be of limited value.[1,2,3]
Standard Treatment Options for Pituitary Carcinomas
Standard treatment options for pituitary carcinomas include the following:
Some reports indicate that as many as 88% of pituitary carcinomas are endocrinologically active, and adrenocorticotrophin hormone-secreting tumors are the most common. Treatments for patients with pituitary carcinomas are palliative, with the mean survival time ranging from 2 years to 2.4 years, though several case reports of long-term survivors have been published.[2,3,4,5]
Treatment options for patients with pituitary carcinomas include resection and dopamine agonists for PRL-producing tumors; somatostatin analogues for GH-producing and TSH-producing tumors; radiation therapy, and chemotherapy. These treatments are palliative with the mean survival time ranging from 2 years to 2.4 years, though several case reports of long-term survivors have been published.[2,3,4,5]
Standard Treatment Options for Recurrent Pituitary Tumors
Standard treatment options for recurrent pituitary tumors include the following:
The question and selection of further treatment for patients who relapse is dependent on many factors, including the specific type of pituitary tumor, prior treatment, visual and hormonal complications, and individual patient considerations.
Treatment Options Under Clinical Evaluation for Recurrent Pituitary Tumors
Treatment options under clinical evaluation for recurrent pituitary tumors include the following:
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Purpose of This Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the treatment of pituitary tumors. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.
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PDQ® Adult Treatment Editorial Board. PDQ Pituitary Tumors Treatment. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/types/pituitary/hp/pituitary-treatment-pdq. Accessed <MM/DD/YYYY>. [PMID: 26389459]
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