Lipomas, Pathology


Article Author:
Ahmad Charifa


Article Editor:
Talel Badri


Editors In Chief:
Evelyn Metz
Julie Sewell
Aditya Arya


Managing Editors:
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Frank Smeeks
Kristina Soman-Faulkner
Benjamin Eovaldi
Radia Jamil
Sobhan Daneshfar
Pritesh Sheth
Hassam Zulfiqar
Steve Bhimji
John Shell
Matthew Varacallo
Ahmad Malik
Mark Pellegrini
James Hughes
Beata Beatty
Hajira Basit
Phillip Hynes
Kavin Sugumar


Updated:
10/27/2018 12:31:41 PM

Introduction

Lipomas are defined as soft masses of adipose (fat) cells which are often encapsulated by a thin layer of fibrous tissue. Clinically, they often present in the cephalic part of the body, specifically in the head, neck, shoulders, and backs of patients, although they can less commonly be seen elsewhere, for example, the thighs. The tumors typically lie in the subcutaneous tissues of patients. The masses are often benign, and while the age of onset can vary, they most often develop between the age of 40 and 60. There is usually no reason for treatment, as they pose no threat to the patient, unless they are uncomfortable, due to being located on joints or if they are rapidly growing, which is uncommon, as the typical lipoma growth is slow.

Lipomas can sometimes, though rare, be associated with certain disorders such as multiple hereditary lipomatosis, Gardner syndrome, adiposis dolorosa, and Madelung disease. Some unconventional forms of lipomas include the following: angiolipoma, chondroid lipoma, lipoblastoma, myolipoma, pleomorphic lipoma/spindle cell lipoma, intramuscular and intermuscular lipoma, lipomatosis of nerve, lipoma of tendon sheath and joint, lipoma arborescens, multiple symmetric lipomatosis, diffuse lipomatosis, adiposis dolorosa, and hibernoma.

Issues of Concern

It is important to distinguish common lipomas from liposarcoma, They share similar characteristics, although the latter poses a greater risk to the patient. As mentioned earlier, while treatment is not always necessary, if it is decided that a patient should seek treatment, then the options are typically steroid injections or excision of the tumor.

Causes

While the etiology of lipomas is unclear, some studies have shown a genetic link, whereby, about two-thirds of lipomas demonstrate genetic abnormalities.

In addition to the possibility of a genetic link, another theory presents the idea that there is a direct positive correlation between trauma to an area and lipoma production. Research shows a link between adipose tumor growth as a post-traumatic event following a direct impact on that area of soft tissue. In addition to the risk factors listed above, other possible connections that may lead to lipomas are obesity, alcohol abuse, liver disease, as well as, glucose intolerance.

Anatomical Pathology

Lipomas are defined as mesenchymal tumors which typically lie subcutaneously. Less commonly, they can also be found on internal organs, such as stomach and bowels. These masses are not typically attached to underlying muscle fascia. Lipomas are composed of lobulated, slow-growing, mature adipose tissue, having a minimal connective tissue stroma. They are commonly enclosed in a thin, fibrous capsule.

Clinical Pathology

Patients often complain of a soft, mobile mass of tissue they can feel under the skin. These are typically painless unless they encroach joints, nerves, or blood vessels. Patients often see these in the upper part of the body. Rarely, these lipomas can form in muscles or organs.

Lipomas are mostly harmless and are only treated or excised if they cause pain due to their location and/or if they are impacting an organ’s function. However, some patients choose to have these masses removed for cosmetic reasons, as they can often be seen through the skin as they lie subcutaneously.

Biochemical and Genetic Pathology

A genetic link has been demonstrated that cites that about two-thirds of lipomas exhibit genetic abnormalities. In a subgroup of lipomas, the HMGA2 gene (located on 12q14.3) was involved in tumor pathogenesis.

The following structural rearrangements of chromosomes have been associated with lipoma occurrence:

  • 12q13-15 region (65%)
  • 13q portion loss(10%)
  • 6p21-23 region (5%)
  • Other loci anomalies or normal karyotype (15-20)

Morphology

Lipomas are composed of adipose/fat tissue, are mobile, soft to the touch, typically painless and present subcutaneously. These are surrounded by a thin, fibrous capsule that is not attached to the underlying muscle fascia. These masses are typically less than 2 inches wide but may be larger. They are commonly singular. However, some patients have more than one. They typically occur in the upper trunk, head, neck, shoulders, and back of patients.

Mechanisms

A possible mechanism of action of lipoma development is post-trauma to the respective area. It has also been theorized that this is true only for traumas that result in necrosis of adipose/fat cells and subsequent local inflammation, and that these are what are responsible for triggering the lipoma formation.

Clinicopathologic Correlations

Fletcher et al. (1996) cited that there exists a clinicopathological correlation between the cytogenetic aberrations and the morphological subtypes of lipoma tumors. They concluded that such a correlation could serve as a significant diagnostic tool in difficult or histologically borderline cases.

Intradural lipomas of the spinal cord have also been shown to reflect a clinicopathological significance, whereby, they occur most frequently in men between the ages of 20 to 40 years and are observed in the thoracic region of the spine, specifically at the cord. Symptoms, as described by respective patients, included pain, sensory changes, paraparesis, and urinary incontinence.

Clinical Significance

While the age of onset for a lipoma varies, it is typically first seen in patients between the ages of 40 to 60, and no gender bias has been documented. Certain types of lipomas are more frequently seen in other age groups, for example, such as hibernomas clinically present around the age of 30, lipoblastomas and diffuse lipomatosis are commonly found in children older than the age of 3. Approximately 5% of patients present with multiple lipomas.

The prevalence of lipomas has been cited as affecting 1% of the population, while its incidence, which is possibly underreported, is 2.1 per 1000 individuals per year.

Positive diagnosis of a lipoma typically involve the following: 

  • Physical exam performed by a medical doctor
  • An ultrasound of the mass should show that the lipoma or adipose mass is deeper than the surrounding fatty tissue, as well as, exhibiting dissimilar features as compared to the healthy/normal adipose tissue present
  • A biopsy (and subsequent analysis of a tissue sample) is not systematically done in routine practice as the diagnosis is generally made clinically, and since it may be difficult to distinguish lipomas from healthy adipose tissue, histologically speaking

Surveillance

If lipomas are not painful and harmless, there is no need for removal. 

Treatment

The techniques used for such include, intralesional transcutaneous sodium deoxycholate (associated or not to phosphatidylcholine) injections, intralesional steroids combined with isoproterenol (a beta-2 adrenergic agonist) injections, liposuction of the tumor, or surgical excision. This latter is likely the most effective method to prevent them from reoccurring, though the encapsulation must also be removed for the most effective treatment and to decrease the risk of reoccurrence. If the decision is made to excise lipomas, then it should be done while the lesions are smaller rather than after they grow larger to reduce the risk of these encroaching on joints, nerves, and blood vessels, thus making the excision more difficult and invasive.

Prognosis

The prognosis for benign lipomas is very good. Once these tumors are excised, mainly for cosmetic reasons, they often do not return. However, is imperative that the fibrous capsule surrounding the lipoma is entirely removed to prevent such from happening.


Interested in Participating?

We are looking for contributors to author, edit, and peer review our vast library of review articles and multiple choice questions. In as little as 2-3 hours you can make a significant contribution to your specialty. In return for a small amount of your time, you will receive free access to all content and you will be published as an author or editor in eBooks, apps, online CME/CE activities, and an online Learning Management System for students, teachers, and program directors that allows access to review materials in over 500 specialties.

Improve Content - Become an Author or Editor

This is an academic project designed to provide inexpensive peer-reviewed Apps, eBooks, and very soon an online CME/CE system to help students identify weaknesses and improve knowledge. We would like you to consider being an author or editor. Please click here to learn more. Thank you for you for your interest, the StatPearls Publishing Editorial Team.

Lipomas, Pathology - Questions

Take a quiz of the questions on this article.

Take Quiz
Corpus callosum lipomas are classified as either curvilinear or tubulonodular. Tubulonodular, not curvilinear, lipomas are most often associated with what clinical finding?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which of the following is not a usual indication for the management of lipoma?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up

Lipomas, Pathology - References

References

Oral fibrolipoma: A report of two cases and review of literature., Phulari RG,Soni V,Talegaon TP,Bakutra G,, Indian journal of dental research : official publication of Indian Society for Dental Research, 2018 Jul-Aug     [PubMed]
Adipose tumors of the heart., Rocha RV,Butany J,Cusimano RJ,, Journal of cardiac surgery, 2018 Aug     [PubMed]
Adenolipoma of the Skin: A Report of 11 Cases., Amir R,Sheikh S,, Case reports in dermatology, 2018 Jan-Apr     [PubMed]
[Lipofibromatosis: a clinicopathological analysis of eight cases]., Lao QY,Sun M,Yu L,Wang J,, Zhonghua bing li xue za zhi = Chinese journal of pathology, 2018 Mar 8     [PubMed]
Lipomas, Pathology, Charifa A,Badri T,,, 2018 Jan     [PubMed]

Disclaimer

The intent of StatPearls is to provide practice questions and explanations to assist you in identifying and resolving knowledge deficits. These questions and explanations are not intended to be a source of the knowledge base of all of medicine, nor is it intended to be a board or certification review of NP-Gerontology Primary Care. The authors or editors do not warrant the information is complete or accurate. The reader is encouraged to verify each answer and explanation in several references. All drug indications and dosages should be verified before administration.

StatPearls offers the most comprehensive database of free multiple-choice questions with explanations and short review chapters ever developed. This system helps physicians, medical students, dentists, nurses, pharmacists, and allied health professionals identify education deficits and learn new concepts. StatPearls is not a board or certification review system for NP-Gerontology Primary Care, it is a learning system that you can use to help improve your knowledge base of medicine for life-long learning. StatPearls will help you identify your weaknesses so that when you are ready to study for a board or certification exam in NP-Gerontology Primary Care, you will already be prepared.

Our content is updated continuously through a multi-step peer review process that will help you be prepared and review for a thorough knowledge of NP-Gerontology Primary Care. When it is time for the NP-Gerontology Primary Care board and certification exam, you will already be ready. Besides online study quizzes, we also publish our peer-reviewed content in eBooks and mobile Apps. We also offer inexpensive CME/CE, so our content can be used to attain education credits while you study NP-Gerontology Primary Care.