The pituitary gland is an uncommon site for metastases, in particular from CRC. Breast and lung cancers are the most common diseases spreading to this site (Morita et al. 1998). Teears and Silverman analysed 88 patients with pituitary metastases and noticed that breast and lung were the most frequent sites of the primary tumor (40% and 33%, respectively), whereas 2% of patients only presented CRC as primary site of disease (Teears and Silverman 1975). In the absence of specific series in the literature, the incidence of rectal cancer metastasizing to the pituitary is certainly even lower.
The widest review of literature about pituitary metastases including 380 patients, mentions 9 cases only of primary localization in colorectal site (Komninos et al. 2004). These data confirm the rarity of our report.
Recent studies reveal that the majority of pituitary metastases occur in the posterior lobe. The same work by Teears and coll., reported that 57% of the lesions are localized to the posterior pituitary alone, 13% to the anterior pituitary alone, 12% to both lobes and the remaining to the capsule or stalk (Teears and Silverman 1975).
The majority of pituitary metastases are clinically silent. When the patient is symptomatic, the most common clinical presentation seems to be diabetes insipidus (DI) (45.2%), reflecting a predominance of metastases to the posterior lobe (Sioutos et al. 1996). Other reported symptoms are ophtalmoplegia, headache, visual field defects and anterior pituitary disfunction (Nelson et al. 1987). Additionally, DI is more common in patients with pituitary metastases than in those with adenomas (Morita et al. 1998). In a series of 190 cases of symptomatic pituitary metastasis, DI was reported in 45.2% of patients, optic nerve impairment in 27.9% and anterior pituitary insufficiency in 23.6% (Komninos et al. 2004). Twenty-one percent of patients developed other cranial nerves defects such as 3rd, 4th, and 6th palsy.
In about 25% of the cases the diagnosis is made after laboratory evidence of anterior pituitary failure (Freda and Post 1999).
Radiological evaluation doesn’t really help in distinguishing adenoma from metatasis. High resolution CT and MRI are the most sensitive exams. CT usually shows a hyperdense or isodense mass, enhancing homogeneously or non-homogeneously (if cystic degeneration, hemorrhage, or necrosis co-exist) in contrast images. MRI may demonstrate an isointense or hypointense mass on T1 weighted images, with a usually high-intensity signal on T2 weighted images, homogeneously enhancing post-gadolinium, as well as absence of high-signal intensity from the posterior lobe on T1. Neither of the imaging findings is highly specific and allows to make a correct diagnosis (Schubiger and Haller 1992). The definitive diagnosis of metastatic involvement is always based on histological evaluation, allowing to distinguish from pituitary primary lesions (Go et al. 2011).
Benign lesions more often are functioning masses, frequently producing ACTH and prolactin; on the other hand, metastases might cause disfunction of the pituitary gland and compression of the near anatomic structures (Max et al. 1981).
Treatment, mostly palliative, depends on the symptoms. Surgical exploration and decompression, alone or combined with radiation, is often necessary when suprasellar extension causes progressive deterioration in vision and/or pain (Branch and Laws 1987). In our case, tumor debulking allowed to improve the local symptoms, especially headache and visual field defects such as diplopia and hemianopsia.
Generally, the surgical approach, the completeness of the resection, and an aggressive treatment (surgery plus local radiation) are associated with better symptom relief but do not affect survival rates; in fact, prognosis of patients with MPs is usually poor, with a life expectancy of few months after diagnosis (Komninos et al. 2004).
The peculiarity of the case described above is not only represented by the unusual site of metastasis from rectal cancer, but also by the long history of treatments received by our patient.
Recent studies show that the expanded treatment options and the consequent improved survival for patients with metastatic CRC are associated with an increased incidence of metastases at uncommon sites (Sundermeyer et al. 2005). A comprehensive review on the incidence, prevalence, epidemiology, risk factors, management, and prognosis of brain metastases arising from esophageal, gastric, gallbladder, pancreatic, small bowel, and colorectal cancer reported that brain metastases are found in 1% of colorectal cancer, 1.2% of esophageal cancer, 0.62% of gastric cancer, and 0.33% of pancreatic cancer cases. Survival in patients with brain metastases from gastrointestinal tumors was found to be inferior compared with breast, lung or kidney. Authors concluded that, although early treatment has been linked to prolonged survival and improved quality of life, brain metastases represent a late manifestation of gastrointestinal cancers and remain an ominous sign (Go et al. 2011).
Sundermeyer and colleagues evaluated patients with metastatic CRC from 1993 to 2002 at the Fox Chase Cancer Center, collecting date of diagnosis/metastasis, primary tumor site, therapeutic agents received, survival, and site(s) of metastases. The data demonstrate that the incidence of bone and brain metastases in patients with CRC is more common than previously reported and is associated with the administration of multiple systemic treatments (Sundermeyer et al. 2005).
In conclusion, here we presented the case of a patient affected by metastatic rectal cancer, with a large sellar mass and a long history of oncological treatments.
The rarity of involvement of the pituitary gland from rectal cancer made diagnosis challenging and the histological evaluation helped to confirm the intestinal origin of the lesion. This metastatic event is very uncommon making almost impossible to perform prospective clinical trials specifically designed to compare different treatment approaches. Thus, only a greater awareness of the problem along with a more accurate and timely diagnosis, will lead to choose the best therapies suitable to the specific patient and in turn improve overall prognosis.
Although infrequently, metastatic involvement of the pituitary gland from colorectal cancer can be found and it might become increasingly common in the next future as a result of the expanded treatment options and the consequent improved patients’ survival.