Myelolipoma

Myelolipoma
Other names	myolipoma
An adrenal myelolipoma
Specialty	Oncology

Myelolipoma (myelo-, from the

Myelolipomas can present in the adrenal gland,^[2] or outside of the gland.^[3]

Signs and symptoms

The majority of myelolipomas are asymptomatic. Most do not produce any adrenal hormones. Most are only discovered as a result of investigation for another problem.^[4]

When myelolipomas do produce symptoms, it is usually because they have become large, and are pressing on other organs or tissues nearby. Symptoms include pain in the

• stroma of the adrenal cortex that are able to differentiate, may reversibly change into fat or blood-forming cells. This might occur because of the actions of adrenal cortex hormones, or of hormones released by the pituitary gland that act on the adrenal glands, such as adrenocorticotropic hormone (ACTH).^[6]
• The blood-forming cells may arise by differentiation of cells within the
  capillaries of the adrenal gland.^[4]
• Myelolipoma simply represents a site of normal blood formation outside the bone marrow.^[4]

Pathology

Macroscopic features

Myelolipomas are usually found to occur alone in one adrenal gland, but not both. They can vary widely in size, from as small as a few millimetres to as large as 34 centimeters in diameter. The cut surface has colours varying from yellow to red to mahogany brown, depending on the distribution of fat, blood, and blood-forming cells. The cut surface of larger myelolipomas may contain haemorrhage or infarction.^[1]

• 
  A macroscopic photograph of an adrenal myelolipoma. A remnant of the adrenal gland can be seen at the top
• 
  The cut surface shows colour variegation from yellow to red to brown depending on the distribution of fat, blood and

  myeloid

  elements

Microscopic features

The typical microscopic features of myelolipomas are shown in the image. There is a mixture of normal adrenal tissue, fat, and a full trilineage maturation of the three major

Most myelolipomas are unexpected findings on

Small myelolipomas generally do not produce symptoms, and do not require treatment. Ongoing surveillance of these lesions by a doctor is recommended. Surgical excision (removal) is recommended for large myelolipomas because of the risk of bleeding complications.[6]

Epidemiology

Myelolipomas are rare. They have been reported to be found unexpectedly at autopsy in 0.08% to 0.4% of cases (i.e.: somewhere between 8 per 10,000 and 4 per 1,000 autopsies). They most commonly occur in the adrenal gland, and comprise about 8% of all adrenal tumours.^[8] They may also occur in other sites, such as the mediastinum, the liver and the gastrointestinal tract.^[1]

There is no gender predilection, males and females are affected equally. The peak age range at diagnosis is between 40 and 79 years of age.^[1]

References