Adrenolipoma overview

# Overview
Adrenolipomas are rare benign neoplasms that histologically consist of fat and bone marrow in varying proportions. In general, they are  small, unilateral, and hormonally inactive. They are rich in adipose tissue and hematopoietic elements. Most lesions are small and asymptomatic. Adrenolipomas are usually detected incidentally in autopsy or by imaging studies performed for other reasons. Most tumors are unilateral, they show no predilection to one peculiar side. Symptoms of adrenolipoma include abdominal pain, haematuria, and abdominal fullness. Surgery is the mainstay of treatment.

# Historical Perspective
Adrenolipoma was first discovered by Gierke in 1905.

# Classification
Myelolipomas are classified into 4 type based on their clinicopathologic patterns:
- Isolated adrenal myelolipoma
- Adrenal myelolipoma with acute hemorrhage
- Extra-adrenal myelolipoma
- Myelolipoma associated with other adrenal diseases.

# Pathophysiology
- Myelolipomas are usually less than 4 cm in size occasionally measuring more than 10 cm in size.
- Extra-adrenal sites for myelolipomas include 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.
- On gross pathologic examination, a cut section of a myelolipoma has a variegated appearance consisting of bright yellow areas of fat, dark red areas of hematopoietic myeloid tissue, and 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

# Causes
There are no established causes for adrenolipoma. However, Adrenal myelolipoma is often associated with conditions which can be considered as adrenal stimulants such as
- Cushing's disease
- Obesity
- Hyperlipidemia
- Hypertension
- Diabetes
- Stressful lifestyle
- Unbalanced diet

# Differentiating Adrenolipoma from other Disease
Adrenolipoma must be differentiated from retroperitoneal liposarcoma, adrenal teratoma, and adrenocortical carcinoma.

# Epidemiology and Demographics
- The incidence of adrenolipoma is approximately 0.8-4 per 100,000 individuals worldwide.
- 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.

# Risk Factors
There are no established risk factors.

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

# Complications
Common complications of adrenolipoma include Cushing syndrome, Conn syndrome, congenital adrenal hyperplasia and retroperitoneal haemorrhage.

# Diagnosis

## History and Symptoms
Symptoms of adrenolipoma include abdominal pain, haematuria, and abdominal fullness.

## Laboratory Findings
There are no associated laboratory findings among the majority of patients with adrenolipoma.

## Abdominal X-Ray
There are no abdominal X-ray findings associated with adrenolipoma.

## CT
Abdominal CT scan may be helpful in the diagnosis of adrenolipoma.

## MRI
Abdominals MRI may be helpful in the diagnosis of adrenolipoma.

## Ultrasonography
On ultrasound, adrenolipoma is characterized by heterogenous mass of mixed hyper- and hypoechoic components.

## Other Diagnostic Studies
Other diagnostic studies for adrenolipoma include fine needle aspiration and fluorodeoxyglucose uptake (FDG).

# Treatment

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

## Surgery
- 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 preventive measurements available for adrenolipoma.