Evaluation and management of pituitary incidentalomas
ABSTRACTA surprising number of apparently healthy people harbor unsuspected pituitary tumors, which are being discovered incidentally on computed tomography (CT) or magnetic resonance imaging (MRI) performed for other reasons. The majority can be safely observed; for others, medical therapy or surgical resection is necessary. In this article we outline our approach.
KEY POINTS
- Two key questions that must be answered when a pituitary incidentaloma is discovered are whether it is hormonally active and whether it is causing a mass effect (eg, a visual field defect due to pressure on the optic chiasm).
- Incidentalomas that are not hormonally active and that are not causing a mass effect can generally be managed by watchful waiting.
- Hormonally active prolactin-secreting tumors can be treated with dopamine agonists. Other hormonally active tumors and those that are causing a mass effect should be surgically removed.
- The risks of further tumor growth and of pituitary apoplexy are higher in tumors that are larger when discovered.
If the tumor is hormonally inactive
If the tumor is hormonally inactive, its further evaluation depends on its size and whether there is a mass effect. In patients with a nonfunctioning pituitary macroadenoma, a comprehensive hormonal evaluation for hypopituitarism should be done. Patients with a visual field defect or cranial neuropathy should undergo surgical tumor resection. If there is no mass effect, observation may be an acceptable strategy. We, and others,1,25 recommend surgery for most patients with pituitary macroadenomas abutting the optic chiasm.
If the tumor is small
If the tumor is small (ie, a microadenoma), the risk of its growing is low. Three small studies followed such patients prospectively and found a 0 to 14% risk of tumor enlargement over a mean follow-up period of 1.8 to 6.7 years.12,25,26 While there is no consensus about how soon to follow up patients with nonfunctioning pituitary microadenomas, we obtain a follow-up MRI study in 1 year, with no further routine imaging if the tumor has remained stable, unless the patient develops symptoms or signs suggesting a mass effect.
If the tumor is large
If the tumor is large (ie, a macroadenoma), the risk of further growth is expected to be higher, since the tumor has already shown the propensity to grow. In the same three series discussed above, the risk of tumor growth for a pituitary macroadenomas was about 30% over the mean follow-up of 1.8 to 6.7 years.12,25,26
Furthermore, several recent studies have suggested a higher propensity to grow and to cause symptoms and signs than previously thought. For example, Karavitaki et al7 studied 24 patients who had nonfunctional macroadenomas and found that the 48-month probability of enlargement was 44%; of this group, 57% showed new or worsening visual field defects, and an additional 21% showed new chiasmatic compression without vision loss. Similarly, Arita and colleagues27 found that 21 (50%) of 42 nonfunctional adenomas (mean size 18.3 ± 7 mm) increased by at least 10% over an average of 32 months after the initial evaluation. Ten patients became symptomatic over a mean of about 5 years, with 4 of these 10 (9.5% of the entire cohort) suffering symptomatic pituitary apoplexy. Therefore, one may argue for surgery (especially in young patients) for pituitary macroadenomas even in the absence of mass effect.
We would obtain a follow-up MRI study at 6 months, then yearly for 5 years, and then every 2 to 3 years if the tumor is stable. Surgery would be indicated if there is evidence of tumor growth or a mass effect.
While tumor growth has been found to be independent of age in some studies,27 others have found longer tumor doubling time in patients older than 60 years.28
The risk of pituitary apoplexy
Pituitary apoplexy results from a hemorrhagic infarction of the tumor and manifests clinically as the sudden onset of severe headache, nausea, vomiting, vision loss, and cranial nerve palsies. While most cases of pituitary apoplexy are spontaneous, precipitating factors may include head injury, anticoagulant therapy, dopamine agonists, radiation therapy, or dynamic endocrine tests.29
It is important to educate patients and their families about the symptoms of pituitary apoplexy, especially patients with pituitary macroadenomas. If the condition is unrecognized and untreated, patients can develop hypotension and shock secondary to adrenal insufficiency, as well as irreversible vision loss or diplopia.
Surgery is generally recommended in cases of progressive vision loss or cranial neuropathy, preferably within 24 or 48 hours of onset if feasible, to minimize the risk of a permanent neurologic deficit.
Clinically significant pituitary apoplexy is rare in patients with pituitary microadenomas. In the study by Arita et al,27 the risk of pituitary apoplexy during 5 years of follow-up was 9.5%, and all of the tumors involved were macroadenomas. This rate is higher than in some other studies, in which the risk of apoplexy ranged from 0.4% to 7% during a mean follow-up of 2 to 6 years.1,25,30
CASE FOLLOW-UP
Since our patient had no evidence of hormonal hypersecretion or mass effect and no hypopituitarism, we asked her to return in 6 months. A repeat MRI study showed the tumor to be stable, with no evidence of growth. The patient was scheduled for a return visit in 1 year.
