Pheochromocytomas are uncommon tumors that originate in the adrenal glands, small organs located above the kidneys. This article clarifies how these tumors typically grow and the factors that can influence their development over time.
Nature of Pheochromocytoma
A pheochromocytoma is a rare neuroendocrine tumor arising from specialized chromaffin cells. These cells are primarily found in the adrenal medulla, though they can occasionally develop outside the adrenal glands in areas known as paraganglia. The defining characteristic of these tumors is their ability to produce and release excessive amounts of hormones, specifically catecholamines like adrenaline (epinephrine) and noradrenaline (norepinephrine). While most pheochromocytomas are benign, they are still considered to have metastatic potential.
Typical Growth Patterns
Pheochromocytomas exhibit a slow growth pattern. These tumors typically take approximately five to seven years to double in volume. However, this growth rate can vary considerably among individuals. For instance, smaller masses, those less than one centimeter, have been observed to grow at a rate of about 0.03 to 0.1 centimeters per year.
The growth rate tends to accelerate as the tumor increases in size. Masses measuring two centimeters or larger may grow at a faster rate, around 0.3 to 0.32 centimeters per year. While the majority of pheochromocytomas grow slowly, some may show more rapid progression, particularly in younger individuals under 50 years of age.
Influences on Growth Progression
Several factors contribute to the variability observed in pheochromocytoma growth. Genetic predispositions play a significant role, with approximately 25% to 40% of cases being hereditary. These inherited conditions include:
Multiple Endocrine Neoplasia type 2 (MEN2)
Von Hippel-Lindau (VHL) disease
Neurofibromatosis type 1 (NF1)
Mutations in succinate dehydrogenase (SDH) genes
The specific genetic mutation can influence the tumor’s behavior, including its growth rate and the likelihood of developing multiple tumors.
The initial size of the tumor at detection also influences its subsequent growth trajectory. Larger tumors tend to grow more quickly than smaller ones. Cellular characteristics, while complex, can also provide clues about growth. For example, certain histological features observed under a microscope, such as high cellularity or the presence of necrosis, might be associated with more aggressive behavior.
Detection and Growth
The growth of a pheochromocytoma is often closely linked to its detection, primarily due to the hormones it produces. As the tumor increases in size, it can lead to higher levels of circulating catecholamines, which in turn cause a range of noticeable symptoms. These symptoms frequently include high blood pressure, headaches, excessive sweating, and a rapid heartbeat.
The onset of these symptoms often prompts medical investigation, leading to the tumor’s discovery. While some individuals may experience consistent symptoms, others might have episodic “attacks” that become more frequent or severe as the tumor grows. In some instances, a pheochromocytoma may be discovered incidentally during imaging scans performed for unrelated health concerns, even before symptoms become pronounced.