Soft tissue

Adipose tissue tumors

Lipoma and variants

Spindle cell / pleomorphic lipoma


Editorial Board Member: Jose G. Mantilla, M.D.
Deputy Editor-in-Chief: Borislav A. Alexiev, M.D.
Laura Warmke, M.D.

Topic Completed: 14 September 2021

Minor changes: 14 September 2021

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed Search: pleomorphic lipoma / spindle cell lipoma[title] soft tissue

Laura Warmke, M.D.
Page views in 2020: 13,246
Page views in 2021 to date: 20,331
Cite this page: Warmke L, Meis J. Spindle cell / pleomorphic lipoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueadiposepleomorphicgeneral.html. Accessed October 21st, 2021.
Definition / general
  • Spindle cell lipoma and pleomorphic lipoma are benign adipocytic tumors, currently regarded as morphologic variants of a single neoplasm
  • Compose approximately 1.5% of all lipomatous tumors (Histopathology 1987;11:803)
  • First described in 1975 by Enzinger and Harvey (Cancer 1975;36:1852)
Essential features
  • Spindle cell lipoma contains a varying mixture of mature adipocytes, bland spindle cells and ropy collagen fibers (Cancer 1975;36:1852)
  • Pleomorphic lipoma also contains pleomorphic and multinucleated floret-like giant cells
Terminology
  • Dendritic fibromyxolipoma (not recommended)
ICD coding
Epidemiology
  • Commonly affects middle aged to elderly men (45 - 70 years) (Cancer 1975;36:1852)
  • Very rare in patients < 20 years
  • < 10% of cases occur in women
  • Uncommon compared with conventional lipoma (ratio = 1:60)
Sites
Pathophysiology
Etiology
Clinical features
  • Asymptomatic
  • Longstanding, mobile lesion in subcutaneous tissue
  • Usually solitary
  • Shawl region of posterior neck / shoulder / upper back (Cancer 1975;36:1852)
  • Small size (most < 5 cm)
Diagnosis
  • Superficial, well circumscribed adipocytic lesion involving characteristic shawl region in a middle aged to elderly man (Cancer 1975;36:1852)
  • Demonstration of CD34 positivity and loss of RB1 helpful
Radiology description
  • MRI
    • Appearance can vary from completely nonfatty to lipoma-like (Clin Radiol 2020;75:396.e15)
    • Findings nonspecific
    • Helpful in determining extent of lesion
    • Fat free variant may be misdiagnosed as sarcoma
Radiology images

Images hosted on other servers:

Sagittal CT of posterior neck swelling

Coronal CT of posterior neck swelling

MRI characteristics

Prognostic factors
  • Benign lesion, no risk of metastasis
  • Local recurrence is rare even with incomplete excision (Cancer 1975;36:1852)
Case reports
Treatment
  • Conservative surgical excision only
Gross description
  • Well circumscribed, oval mass in subcutaneous tissue (Semin Diagn Pathol 2019;36:105)
  • Yellow-tan cut surface with grey-white and myxoid foci
  • Texture firmer than ordinary lipoma
  • Dermal and intramuscular tumors may have an infiltrative appearance
Gross images

Images hosted on other servers:

Excised tumor

Bisected surface whiter than typical lipoma

Frozen section description
  • Mature adipocytes mixed with bland spindle cells
Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Laura Warmke, M.D., Jeanne Meis, M.D. and AFIP images

Spindle cell lipoma

Myxoid change

(Pseudo)
angiomatous appearance

Fat poor subtype

Myxofibrosarcoma-like appearance


Cellular spindle cell lipoma

Pleomorphic lipoma with myxoid change

Pleomorphic lipoma

CD34 positivity

RB1 loss

Virtual slides

Images hosted on other servers:

Conventional spindle cell lipoma

Spindle cell lipoma with myxoid change

Pleomorphic lipoma

Cytology description
  • Mixture of mature adipocytes, uniform spindle cells and collagen fibers (Cancer 2001;93:381)
  • Spindle cell nuclei fusiform to ovoid with poorly defined, bipolar cytoplasmic processes
  • Nuclear grooves may be present
  • Myxoid background with mast cells common
  • Mitotic activity and nuclear pleomorphism typically absent
  • Multinucleated giant cells in pleomorphic lipoma
Cytology images

Contributed by Laura Warmke, M.D.

Bland spindle cells

Mature adipocytes



Images hosted on other servers:

Spindle / wavy nuclei

Wavy collagen fibers

Mast cells

Myxoid change

Positive stains
Negative stains
Electron microscopy description
  • Spindle cells with some features of fibroblasts
  • Nonmembrane bound lipid droplets, suggesting possible prelipoblastic nature (Cancer 2001;93:381)
Electron microscopy images

Images hosted on other servers:

Ultrastructural study

Molecular / cytogenetics description
Molecular / cytogenetics images

Images hosted on other servers:

Karyogram

Videos

Spindle cell lipoma

Pleomorphic lipoma

Sample pathology report
  • Soft tissue, back, excision:
    • Spindle cell lipoma (see comment)
    • Comment: Sections show a benign adipocytic neoplasm with bland spindle cells and eosinophilic collagen bundles in a myxoid background with scattered mast cells. No necrosis, marked cytologic atypia or significant mitotic activity is identified. Immunohistochemical stains show that the spindle cells are diffusely positive for CD34, while demonstrating loss of RB1. These results support the above diagnosis.
Differential diagnosis
Board review style question #1

What is the most typical clinical presentation of a patient with a spindle cell lipoma?

  1. 30 year old woman soft tissue mass (9 cm) involving her right lateral thigh
  2. 45 year old woman with subcutaneous mass (3 cm) involving her left arm
  3. 55 year old man with subcutaneous mass (4 cm) involving his upper back
  4. 60 year old man with soft tissue mass (15 cm) involving his retroperitoneum
Board review style answer #1
C. 55 year old man with subcutaneous mass (4 cm) involving his upper back. Spindle cell lipoma usually occurs in middle aged to elderly men. The lesion is often small (< 5 cm) and frequently involves the subcutaneous tissue of the upper back, shoulder or posterior neck.

Comment Here

Reference: Spindle cell / pleomorphic lipoma
Board review style question #2

What 2 immunohistochemical stains may be helpful in confirming the diagnosis of spindle cell lipoma?

  1. CD34 positive and RB1 loss
  2. CD34 positive and STAT6 positive
  3. Desmin positive and RB1 loss
  4. MDM2 positive and CDK4 positive
Board review style answer #2
A. Spindle cell lipoma is diffusely positive for CD34 and demonstrates loss of expression of RB1. Atypical lipomatous tumor / well differentiated liposarcoma is positive for both MDM2 and CDK4. Solitary fibrous tumor is positive for both CD34 and STAT6. Desmin positivity and loss of expression of RB1 can be seen in mammary type myofibroblastoma.

Comment Here

Reference: Spindle cell / pleomorphic lipoma
Back to top
Image 01 Image 02