Adrenal myelolipoma
Synonyms and keywords:Adrenal myelolipoma; Myelolipoma of adrenal gland; Adrenal myelolipomata; Myelolipoma

# Overview
Adrenal myelolipoma is a  benign tumor of the adrenal gland. It mainly consists of mature adipose tissue and intermixed myeloid tissue. Adrenal myelolipoma are the second most common cause of adrenal incidentillomas and make up almost 10% of  it. Rarely, myelolipomas are encountered outside the adrenal glands and are termed as extra adrenal myelolipomoas.

# Historical Perspective
Adrenal myelolipoma was first discovered by Gierke in 1905.

# Classification
Myelolipomas are classified into 4 types based on their clinical and pathologic patterns:
- Isolated adrenal myelolipoma
- Adrenal myelolipoma with acute hemorrhage
- Extra-adrenal myelolipoma
- Myelolipoma associated with other adrenal diseases

# Pathophysiology

### Gross pathology
- Adrenal myelolipomas are usually less than 4 cm in size; however, they could grow more than 10 cm in size sometimes.
Myelolipomas can occur in extra-adrenal sites such as the retroperitoneum, thorax, and pelvis.
Usually unilateral however they can also involve both adrenals.
- Myelolipomas can occur in extra-adrenal sites such as the retroperitoneum, thorax, and pelvis.
- Usually unilateral however they can also involve both adrenals.
- One hypothesis suggests that stimuli, such as necrosis, inflammation, infection, or stress could cause adrenocortical cell metaplasia
If chronically present these stimulants lead to the development of neoplasms.
This hypothesis is supported by the increased incidence of the lesion in the advanced years of life
- If chronically present these stimulants lead to the development of neoplasms.
- This hypothesis is supported by the increased incidence of the lesion in the advanced years of life
- On gross pathologic examination, a cut section of a myelolipoma has
Variegated appearance consisting of bright yellow areas of fat
Dark red areas of hematopoietic myeloid tissue
Areas with intermixed red and yellow components.
- Variegated appearance consisting of bright yellow areas of fat
- Dark red areas of hematopoietic myeloid tissue
- Areas with intermixed red and yellow components.
- On histopathologic examination, myelolipomas are predominantly composed of fatty areas with interspersed hematopoietic tissue components.
These fatty elements and hematopoietic areas may be clearly separated, or they are often intermixed.
Tissue analysis often reveals a variable amalgamation of myeloid and erythroid cells, megakaryocytes, and occasionally lymphocytes.
In an isolated adrenal myelolipoma, a peripheral rim of normal adrenal cortical tissue can be commonly identified distinctly from the mass.
Rarely the myelolipomas can contain osteoid tissue in addition to the myeloid tissue.
The hemorrhagic areas may be partly replaced by fibrotic tissue or may undergo calcification
- These fatty elements and hematopoietic areas may be clearly separated, or they are often intermixed.
- Tissue analysis often reveals a variable amalgamation of myeloid and erythroid cells, megakaryocytes, and occasionally lymphocytes.
- In an isolated adrenal myelolipoma, a peripheral rim of normal adrenal cortical tissue can be commonly identified distinctly from the mass.
- Rarely the myelolipomas can contain osteoid tissue in addition to the myeloid tissue.
- The hemorrhagic areas may be partly replaced by fibrotic tissue or may undergo calcification

### Microscopic pathology
- Histological examination demonstrates:
Variable amounts of mature adipocytes (with distended lipid vacuoles) similar to bone marrow
Variable amounts of hematopoietic cells (including cells from myeloid, erythroid and megakaryocytic cells lines)
- Variable amounts of mature adipocytes (with distended lipid vacuoles) similar to bone marrow
- Variable amounts of hematopoietic cells (including cells from myeloid, erythroid and megakaryocytic cells lines)

# Causes
The exact causes of Adrenal myelolipoma remain unknown. However, Adrenal myelolipoma is often associated with conditions that can be considered as adrenal stimulants such as:
- Cushing's disease
- Obesity
- Hyperlipidemia
- Hypertension
- Diabetes
- Stressful lifestyle
- Unbalanced diet

# Differentiating adrenal myelolipoma from Other Diseases
Adrenal myelolipoma should be differentiated from other adrenal masses such as:
- Retroperitoneal liposarcoma
- Fat containing adrenocortical carcinoma
- Adrenal teratoma
- Renal angiomyolipoma (AML)

# Epidemiology and Demographics
- The incidence of adrenolipoma is approximately 0.8-4 per 100,000 individuals worldwide.
The increased prevalence of adrenal myelolipomas is due to increased detection because of wider accessibility of computed tomography (CT) and magnetic resonance imaging (MRI) scans.
- The increased prevalence of adrenal myelolipomas is due to increased detection because of wider accessibility of computed tomography (CT) and magnetic resonance imaging (MRI) scans.
- Adrenolipoma affects men and women equally.
- Adrenolipomas are usually recognized in adults, either incidentally at ultrasound or computed topography or may present with vague abdominal symptoms if complicated by hemorrhage.
- Adrenal myelolipomas are the second most common adrenal incidentalomas comprising of 6-16% of adrenal incidentalomas.
- They have an approximate autopsy prevalence of 0.08% to 0.2%.
- They are usually recognized in adulthood with a medican age of diagnosis around 51 years. There is no gender predilection.
- There may be a slight right sided predilection as reported by some studies.

# Risk Factors
There are no established risk factors for Adrenal myelolipoma.

# Screening
There is insufficient evidence to recommend routine screening for Adrenal myelolipoma.

# Natural History, Complications, and Prognosis
- Functional adrenolipomas are associated with endocrine disorders such as:
Cushing syndrome
Congenital adrenal hyperplasia
Conn syndrome
- Cushing syndrome
- Congenital adrenal hyperplasia
- Conn syndrome
- Large adrenolipomas  can cause retroperitoneal haemorrhage or infarction

# Diagnosis

## Diagnostic Study of Choice
The diagnosis of Adrenal myelolipoma is made when a biopsy shows

## History and Symptoms
The most common presenting symptoms for adrenal myelolipomas are as follows:
- Abdominal pain
- Hypochondrial pain
- Flank pain
- Abdominal mass
Rarely, dyspnea, back pain, fever, weight loss, and virilization can be the presenting symptoms of adrenal myelolipomas.

## Physical Examination
Common physical examination findings of Adrenal myelolipoma include:

## Laboratory Findings
There are no associated laboratory findings among the majority of patients with adrenolipoma, some laboratory findings may include:
- Elevated cortisol level (suggestive of Cushing syndrome)
- Elevated aldosteron level (suggestive of Conn's syndrome)

## Electrocardiogram
There are no ECG findings associated with Adrenal myelolipoma.

## X-ray
There are no x-ray findings associated with Adrenal myelolipoma.

## Echocardiography or Ultrasound
Adrenal myelolipoma has the typical appearance of a hyperechoic mass with intermixed hypoechoic regions.
- Echogenicity is mainly determined by the variable proportions of the constituent elements in the lesion. The areas of intermixed fatty and myeloid tissue are the most echogenic, whereas regions of pure fat may appear hypoechoic.
- Because of inhomogeneous architecture, myelolipomas often have heterogeneous echogenicity.
- Calcification foci appear hyperechoic with acoustic shadowing.
- Myelolipoma has vague and no appreciable margins due having almost the same echogenicity as surrounding retroperitoneal fat.
- Hemorrhage alters the sonographic picture, with hemorrhagic areas appearing hypoechoic compared with fat

## CT scan
Abdominal CT scan may be helpful in the diagnosis of Adrenal myelolipoma. Findings on CT scan suggestive of/diagnostic of Adrenal myelolipoma include

## MRI
There are no MRI findings associated with Adrenal myelolipoma.

## Other Imaging Findings
There are no other imaging findings associated with Adrenal myelolipoma.

## Other Diagnostic Studies
There are no other diagnostic studies associated with Adrenal myelolipoma.

# Treatment

## Medical Therapy
There is no treatment for Adrenal myelolipoma; the mainstay of therapy is supportive care.

## Surgery
Surgery is not the first-line treatment option for patients with Adrenal myelolipoma. Surgery is usually reserved for patients with either
- Surgery is the mainstay of treatment of large adrenolipomas. Management of adrenal myelolipoma is decided based upon the size of lesion and presence of symptoms.
- Small lesions measuring less than 5 cm, and those who are asymptomatic are usually monitored via imaging over a period of one to two years.
- Symptomatic tumors or myelolipomas larger than 7 cm should undergo elective surgical excision.
The approach is based on the reported incidence of life-threatening emergencies caused by spontaneous rupture and hemorrhage within large lesions.
Conventional or endoscopic access may be chosen according to the size of the tumor.
Mini-invasive and endoscopic techniques are best utilized for smaller-sized lesions, depending on the expertise of the operator.
Conventional methods including transabdominal, lumbar, subcostal or posterior access laparotomy operations have all been described in the literature.
An extraperitoneal approach is preferable as it leads to quicker recovery of the patient and lesser postoperative complications.
The midline approach is indicated for masses larger than 10 cm or in cases where there are adhesions and infiltration of the surrounding structures.
Follow up is mandatory regardless of which surgical method has been employed.
- The approach is based on the reported incidence of life-threatening emergencies caused by spontaneous rupture and hemorrhage within large lesions.
- Conventional or endoscopic access may be chosen according to the size of the tumor.
- Mini-invasive and endoscopic techniques are best utilized for smaller-sized lesions, depending on the expertise of the operator.
- Conventional methods including transabdominal, lumbar, subcostal or posterior access laparotomy operations have all been described in the literature.
- An extraperitoneal approach is preferable as it leads to quicker recovery of the patient and lesser postoperative complications.
- The midline approach is indicated for masses larger than 10 cm or in cases where there are adhesions and infiltration of the surrounding structures.
- Follow up is mandatory regardless of which surgical method has been employed.

## Primary Prevention
There are no established measures for the primary prevention of Adrenal myelolipoma.

## Secondary Prevention
There are no established measures for the secondary prevention of Adrenal myelolipoma.