Pituitary Gland Cancer (Carcinoma of the Pituitary gland)

What is Pituitary Gland Cancer?

Pituitary gland cancer presents in the pituitary gland.The pituitary gland is a small gland situated in the "sella turcica", a bony cavity at the base of the brain. It is connected to the hypothalamus by the pituitary stalk. The optic chiasm (part of the visual pathway) lies between the pituitary and the hypothalamus. The pituitary can be divided into two parts - the anterior pituitary and the posterior pituitary. Between them, the hypothalamus and pituitary control many of the peripheral hormone systems. The hypothalamus controls pituitary hormone secretion.The anterior pituitary secretes:

Growth hormone;
Adrenocorticotropin (controls cortisol secretion by adrenal gland so affects glucose, protein and fat metabolism);
Thyroid stimulating hormone (regulates thyroid hormone release);
Prolactin (promotes mammary gland development and milk production); and
Follicle stimulating hormone and luteinising hormone (control the growth, hormonal and reproductive activities of the gonads).

The posterior pituitary secretes:

Antidiuretic hormone (controls the rate of urinary water excretion and hence regulates body fluid composition); and

Oxytocin (promotes myoepithelial cell contraction in the delivery of milk from the glandular tissue to the nipple during suckling).The pituitary gland exerts considerable control over many of the hormonal systems acting within the body.

Statistics on Pituitary Gland Cancer?

Pituitary gland cancer is exceedingly rare. However, pituitary adenomas (benign monoclonal proliferations of pituitary tissue) are common, accounting for 10% of intracranial neoplasms, incidental pituitary adenomas are found and occurs with increasing age. As is the case with pituitary adenomas, there is a peak incidence in the 4th to 6th decades with sex incidence being equal.Geographically, the pituitary gland tumour is found worldwide.

Risk Factors for Pituitary Gland Cancer

The vast majority of pituitary neoplsms are adenomas and occur as isolated lesions with unknown aetiology (cause). However, up to 3% of lesions occur in association with the familial syndrome Multiple Endocrine Neoplasia type 1. Other genes have been implicated in the formation of pituitary adenomas, including Gs-alpha, Pttg and FGF receptor-4. The very high incidence of these tumours in autopsy series (up to 25%) highlights the fact that only very few reach clinical significance - either through hormone elaboration or suppression of surrounding normal tissue. There are no known aetiological factors in the development of either pituitary adenomas or carcinomas. The distinction between benign and malignant pituitary neoplasms can only reliably be made on the finding of metastatic spread.

Progression of Pituitary Gland Cancer

The pituitary gland tumour spreads by direct extension. Although truly a neoplastic lesion by virtue of its monoclonal makeup, pituitary adenomas are benign lesions. Spreading is through direct expansion of the tumour mass with extension into adjacent structures - cavernous and sphenoid sinuses, or suprasellar extension with compression of the optic chiasm. Pituitary gland cancers spread through either cerebrospinal fluid or through the blood. Deposits can occur in the central nervous system, the liver, lymph nodes, lung, bone and myocardium.

How is Pituitary Gland Cancer Diagnosed?

General investigations may show no abnormality. Anaemia may occur in long standing cases.

Prognosis of Pituitary Gland Cancer

Although the vast majority of pituitary tumours are benign, the intracranial location of these tumours brings with it certain implications. In functional pituitary gland tumours, the effects of the hormonal hypersecretion may have widespread effects on daily function - and can in themselves carry significant morbidity and mortality. Examples include hyperprolactinaemia (prolactinoma), acromegaly(somatotrophic adenoma), Cushing's disease etc. The mass effects of the tumours in patients with macroadenomas tend to be those arising from compression of neurological structures - bitemporal hemianopia being the classic presentation following suprasellar extension and compression of the optic chiasm. Other sequelae can range from diplopia through CN III compression, to progressive increases in intracranial pressure and eventual herniation of cerebral contents with devastating effects on functional capacity. However, the vast majority of pituitary adenomas go undiagnosed throughout life. Of those that are diagnosed, most are easily and successfully treated through a combination of surgical, medical and radiotherapeutic approaches. In order for the diagnosis of a pituitary carcinoma to be made, metastatic deposits must already be present. This has important implications for prognosis because the disease is no longer confined to the pituitary region.

How is Pituitary Gland Cancer Treated?

Treatment of pituitary neoplasms involves surgery, radiotherapy and drug therapy. Not all tumours require treatment - as is evidenced by the high incidence of pituitary neoplasms discovered incidentally at autopsy. In tumours that require treatment, surgery is often the first line approach where significant extension beyond the sella turcica are causing visual or other symptoms. Radiotherapy can be used as the primary treatment of pituitary tumours or as an adjunct to surgery. Medical therapy involves the replacement of hormones in hypopituitarism or suppression of hormone release in functional tumours.Improvement in symptoms is an important measurement. Specific monitoring may be by measurement of serum hormone levels or through serial imaging of the pituitary.The symptoms that may require attention are those of hormone excess or deficiency as discussed above, as well as those from involvement of adjacent structures such as the optic chiasm and cranial nerves. In addition, in more aggressive tumours and carcinomas, somatic pain from bony infiltration or metastases, visceral pain from liver or lung metastases and neurogenic pain if nerve tissue is compressed will require treatment.