A sellar mass is a growth or tumor located in the sella turcica, a small, bony depression at the base of the skull. This area houses the pituitary gland, an organ that regulates many of the body’s hormones. A mass here can cause symptoms by physically pressing on nearby structures or by interfering with hormone production. The vast majority of growths found in the sellar region are benign and non-cancerous.
Anatomical Context of the Sella
The sella turcica, which translates from Latin as “Turkish saddle,” is a saddle-shaped indentation in the sphenoid bone at the base of the skull. This bony enclosure protects the pituitary gland, often referred to as the “master gland” of the endocrine system. The pituitary releases hormones that control other glands throughout the body, regulating growth, metabolism, stress response, and reproductive function.
The significance of a sellar mass comes from the surrounding structures in this confined space. Directly above the sella is the optic chiasm, the point where the optic nerves from both eyes cross. Upward growth of a mass can compress this visual pathway, directly impacting sight.
Lateral to the sella turcica are the cavernous sinuses, which contain important cranial nerves responsible for eye movement and sensation, along with the internal carotid artery. A mass that expands outward can infringe upon these nerves, potentially causing double vision or facial numbness.
Classification of Sellar Masses
The most common type of sellar mass is the pituitary adenoma, a benign tumor arising from the pituitary glandular tissue, accounting for 85% to 90% of all sellar lesions. They are classified by size: microadenomas measure less than 10 millimeters, and macroadenomas exceed 10 millimeters. Most pituitary adenomas are slow-growing and remain confined to the sella turcica.
Adenomas are further categorized as functional (secreting) or non-functional (non-secreting) types. Functional adenomas secrete an excess of one or more pituitary hormones, often causing symptoms even when the mass is small. Prolactinomas, which secrete prolactin, are the most frequent type of functional adenoma.
Other functional adenomas secrete growth hormone, leading to acromegaly in adults or gigantism in children, or adrenocorticotropic hormone (ACTH), which causes Cushing’s disease. In contrast, non-functional adenomas do not secrete active hormones and are often only discovered when they grow large enough to cause symptoms from their physical size.
Other growths can occur in the sellar region, though they are much less common. These include craniopharyngiomas, which are cystic and calcified tumors arising from embryonic remnants. Meningiomas and Rathke’s cleft cysts, which are non-neoplastic fluid-filled sacs, also make up a small percentage of sellar masses.
Symptoms Caused by Sellar Growths
Sellar masses create problems through two distinct mechanisms: the physical effects of their size (“mass effect”) and the disruption of normal hormone production (“hormonal imbalance”). Symptoms from mass effect typically arise when the growth expands beyond the confines of the sella, which is more common with macroadenomas.
Compression of the optic chiasm often results in a gradual loss of peripheral vision, known as bitemporal hemianopsia. Patients may also experience headaches, or if the mass grows outward, compression of eye movement nerves can cause double vision or ophthalmoplegia.
The second category of symptoms stems from hormonal imbalance, manifesting as either an overproduction or an underproduction of hormones. Overproduction occurs with functional adenomas, such as prolactinomas, which cause irregular menstrual cycles and milky discharge in women, and reduced libido and erectile dysfunction in men. Growth hormone-secreting tumors cause features like the enlargement of hands and feet, changes in facial features, and excessive sweating.
Alternatively, a large mass can damage the normal pituitary tissue, leading to a deficiency in one or more hormones, a condition called hypopituitarism. This hormonal shortage can cause non-specific symptoms, including persistent fatigue, unexplained weight changes, intolerance to cold, and disruptions in reproductive function.
Identifying and Treating Sellar Masses
Identifying a sellar mass typically begins when a patient presents with vision changes or hormonal abnormalities. Magnetic Resonance Imaging (MRI) is the preferred diagnostic tool, providing detailed anatomical views of the soft tissues. MRI helps to precisely locate, measure, and characterize the mass, and identify any compression of the optic chiasm.
In addition to imaging, blood tests assess the endocrine function of the pituitary gland. These tests measure hormone levels to determine if the mass is functional and to check for hormone deficiencies. This combined anatomical and biochemical assessment guides the treatment plan.
Treatment strategies vary based on the mass type, size, and symptoms. For certain masses, particularly prolactinomas, medication can be highly effective at shrinking the tumor and normalizing hormone levels.
For most other symptomatic sellar masses, surgical removal is the standard course of action, often performed using a minimally invasive transsphenoidal approach through the nasal cavity. Radiation therapy, including stereotactic radiosurgery, may be used as a secondary treatment if surgery is unsuccessful or if the mass recurs.