Pituitary carcinoma is a rare and aggressive cancer originating in the pituitary gland, a small organ at the base of the brain. Unlike most pituitary tumors, which are benign, carcinoma is malignant and can spread to other parts of the body, including the brain, spinal cord, or distant organs.
Understanding Pituitary Carcinoma
Pituitary carcinoma is defined by its ability to metastasize, spreading to non-contiguous sites in the central nervous system or distant body parts. This distinguishes it from common pituitary adenomas, which are typically benign and do not spread beyond the skull, though they can be invasive and grow into surrounding structures. Diagnosis of pituitary carcinoma is confirmed only when the tumor has metastasized, as its microscopic appearance can be similar to an adenoma.
Pituitary carcinomas often produce hormones, similar to many adenomas, and are called “functioning” tumors. They are categorized by the specific hormones they produce, such as prolactin (prolactinomas), growth hormone (somatotropinomas), and ACTH (corticotropinomas). Lactotroph (prolactin-secreting) and corticotroph (ACTH-secreting) carcinomas are the most common types, each accounting for about one-third of cases.
The median age for diagnosis is 44 to 45 years. The time for an adenoma to transform into a carcinoma or for metastasis to appear varies, with a median latency period of 5 to 7.5 years. While somatotroph (growth hormone-producing) tumors are rarely malignant and distant metastases are uncommon, corticotroph and prolactin-secreting carcinomas have a higher incidence of systemic dissemination, with rates of 71% and 57% respectively.
Recognizing the Signs
Symptoms of pituitary carcinoma stem from two primary mechanisms: excessive hormone production by the tumor or physical pressure (mass effect) on nearby structures. These non-specific symptoms often resemble other medical conditions, which can sometimes delay diagnosis.
When the carcinoma produces excess hormones, symptoms depend on the specific hormone. For instance, overproduction of ACTH can lead to Cushing’s disease, characterized by weight gain in the face, chest, and abdomen, purple stretch marks, increased hair growth, and high blood pressure. If the tumor secretes too much growth hormone, adults may experience acromegaly, causing enlargement of the skull, facial bones, jaw, hands, and feet, along with joint pain and increased sweating. In children, excessive growth hormone can result in gigantism, leading to rapid growth and unusual height.
Prolactin-secreting carcinomas can cause amenorrhea (cessation of menstrual periods) and abnormal breast milk production (galactorrhea) in women, while men might experience breast growth, erectile dysfunction, and decreased sex drive. Tumors producing thyroid-stimulating hormone (TSH) can lead to symptoms of an overactive thyroid, including nervousness, anxiety, weight loss, and a rapid heartbeat. Beyond hormonal effects, the tumor’s physical presence can cause headaches and vision problems like blurred vision, double vision, or loss of peripheral vision due to pressure on the optic nerves or optic chiasm. Dizziness, facial numbness or pain, nausea, and vomiting can also occur.
Diagnosis and Treatment Approaches
Diagnosing pituitary carcinoma involves imaging studies, hormone level testing, and a biopsy to confirm malignancy. An MRI of the brain is the preferred imaging technique, detecting pituitary tumors and providing detailed information about their size and location. A CT scan may also be used, particularly for surgical planning.
Blood and urine tests measure hormone levels, indicating over or underproduction. For example, high ACTH levels may be investigated with a 24-hour urine collection to assess cortisol or other specialized tests to pinpoint the source. A biopsy, often obtained during surgical removal, is required to confirm the cancerous nature of the growth, as pituitary carcinomas can appear similar to benign adenomas under a microscope. This helps differentiate a true carcinoma from an aggressive adenoma.
Treatment for pituitary carcinoma is highly individualized and often multidisciplinary due to its aggressive nature and rarity. Surgical removal of the tumor is the initial treatment if feasible, and surgery may also address tumors that have spread. Radiation therapy, including stereotactic radiosurgery which delivers highly focused radiation beams to the tumor, may be used after surgery or for patients not eligible for surgery. These treatments aim to control tumor growth, shrink it, or alleviate symptoms.
Systemic therapies, such as chemotherapy, are also considered, with temozolomide often being the first-line drug, sometimes administered alongside radiation therapy. Given its rarity, participation in clinical trials for new treatments can be a valuable option.
Prognosis and Long-Term Care
The prognosis for individuals with pituitary carcinoma is guarded due to its aggressive nature and its tendency to metastasize. Despite multiple treatment modalities, these tumors are often resistant to therapy and can recur. Patients with systemic metastases have a median survival measured in months, while those with metastases confined to the central nervous system may live longer, with an average survival of approximately 2.6 years.
Long-term care involves ongoing monitoring and follow-up to detect any tumor recurrence or new metastases. This includes regular imaging studies, such as MRI, and consistent checks of hormone levels. Management of pituitary carcinoma requires a multidisciplinary team, with treatment plans adjusted over time based on the tumor’s response and progression.