Stanford School of Medicine

Surgical Pathology Criteria

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Spindle Cell Lipoma


  • Predominantly subcutaneous lesion composed of mature fat and bland spindle cells

Diagnostic Criteria

  • If subcutaneous, must be located in posterior neck, upper back and shoulders
    • Well circumscribed in these locations
    • If located in other sites, must be restricted to dermis or submucosa
      • Most reported in thigh, groin, buttock, face, hands, oral
      • Less frequently encapsulated
  • Variable amount of adult fat
    • 10-90% of lesion
      • Rare lesions lacking fat have been reported (see below)
    • No lipoblasts
  • Small bland spindle cells with scant cytoplasm
    • Elongate nuclei
    • Mitotic figures absent
  • Spindle cells arranged in short parallel arrays
    • "School of fish"
    • Nuclei may palisade
  • Bundles of dense ropey collagen
  • Stroma may be myxoid
    • Vessels may be prominent, arborizing, thick walled
    • Cartilaginous and osseous metaplasia reported in one case
  • CD34 positive, usually extensive
  • Mast cells may be numerous
  • Variants may have distinctive patterns
    • Vascular spindle cell lipoma
      • Branching dilated or cleft like-spaces
        • Papillary projections of tumor cells into the spaces
        • Spaces usually cell free
      • Spaces lined by endothelial cells with lymphatic phenotype
        • D2-40 positive, CD31 focal or negative
      • Previously termed pseudovascular spindle cell lipoma
        • Based on studies without D2-40
      • Recognized based on location, areas of typical spindle cell lipoma patterns and CD34 positvity
    • Fibrous spindle cell lipoma
      • Abundant fibrous stroma
      • Bundles of collagen
      • EVG negative
      • Recognized based on location, areas of typical spindle cell lipoma patterns and CD34 positvity
    • Fat free (or almost free)
      • May include above variant patterns
      • May be predominantly myxoid
      • Plexiform or curvilinear vasculature and vascular hyalinization may be prominent
      • Recognized by location, CD34 reactivity and presence of areas with typical features of spindle cell lipoma
    • Rare tumors combined with hibernoma have been reported
      • No distinct clinical features
  • Frequent histologic overlap with pleomorphic lipoma
    • Occasional to frequent cells with large atypical nuclei
    • If pleomorphic features present, diagnosis is restricted to posterior neck, upper back and shoulders
  • May form a spectrum with Mammary Type Myofibroblastoma and Ccellular Angiofibroma
    • All have deletion or rearrangement of 13q14 with loss of nuclear Rb
    • All are benign

Mammary Type Myofibroblastoma

Spindle Cell Lipoma

Cellular Angiofibroma

Usually diffuse collagen

Ropey collagen

Wispy collagen with prominent round vessels

Desmin positive

Desmin negative

Desmin variable

All are CD34 positive with loss of Rb due to 13q14 abnormalities;  all are benign

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting : July 29, 2007
Last update: 3/14/16

Supplemental studies


CD34 100%, generally extensive
bcl2 70-100%
CD99 positive
S100 fat cells only
Desmin 4/25 positive
Smooth muscle actin negative
CD31, D2-40 spindle cells negative
Rb negative (loss of staining)


Immunohistochemistry of lipomatous tumors
  MDM2 CDK4 p16
Atypical lipomatous tumor 45-100% 84-92% 78-97%
Dedifferentiated liposarcoma 55-95 90-100 90
Myxoid / round cell liposarcoma 0-4 0-4 0
Pleomorphic liposarcoma 0 0 0
Lipoma 0-4 0-2 0
Spindle cell and pleomorphic lipoma 0-25 0-6 20
Angiomyolipoma 0 0  
Hibernoma 0 0 positive, variable
Lipoblastoma 0 (1 case) 0 (1 case) positive (1 case)

Genetic analysis

  • Spindle cell lipopma and pleomorphic lipoma demonstrate the same genetic findings
    • Abnormalities of chromosome 16 resulting in deletions of 16q13-qter
    • Frequent deletions within 13q
FISH/PCR of lipomatous tumors
Atypical lipomatous tumor 90-100% 72-100% 75-100% 69-100%
Dedifferentiated liposarcoma 100% 100% 100% 100%
Myxoid liposarcoma 20%      
Spindle cell / pleomorphic lipoma Negative Negative Negative Negative
Angiolipoma Negative      
Lipoma, NOS Negative Negative Negative Negative
Sarcomas 0-40% 0% 0% 0%
  • Spindle cell / pleomorphic lipoma showed 89% chromosome 12 polysomy
  • Differential Diagnosis

    Spindle Cell Lipoma vs. Pleomorphic Lipoma

    • We consider these to be part of a spectrum
    • Mixtures are common
    • If atypical cells are present, location becomes definitional
      • Restricted to posterior neck, upper back, shoulders

    Spindle Cell Lipoma Angiolipoma
    Predominantly back of neck, upper back, shoulders Very rare on neck, upper back
    Usually solitary Frequently multiple
    CD34 positive CD34 stains only endothelium and scattered cells
    Prominent spindle cell component Prominent vascularity
    No fibrin thrombi Frequent fibrin thrombi
    May contain pleomorphic cells (admixed pleomorphic lipoma) No pleomorphic cells

    Spindle Cell Lipoma Ectopic Hamartomatous Thymoma
    Lacks epitihelioid nests Has epithelioid nests
    Has ropy collagen Lacks ropy collagen
    Keratin, p63 and smooth muscle actin negative Keratin, p63 and smooth muscle actin positive
    Both contain spindle cell and adipose components and both are CD34 positive in the spindled component

    Spindle Cell Lipoma Fibrolipoma
    Predominantly back of neck, upper back, shoulders Various locations
    Prominent spindle cell component Lacks prominent spindle cells
    CD34 positive CD34 negative
    Ropy bundles of collagen Lacks ropy collagen

    Spindle Cell Lipoma Fibrolipomatous Hamartoma of Nerve
    Predominantly back of neck, upper back, shoulders Usually involves median nerve
    Does not involve nerves Infiltrates and surrounds large nerve
    Usually age 40-70 Presents under age 30
    No neural symptoms Neural symptoms

    Spindle Cell Lipoma Myolipoma
    Restricted to back of neck, upper back, shoulders Predominantly pelvic
    Scant cytoplasm Tapered cytoplasm in spindle cells
    Ropey collagen frequent No ropey collagen
    CD34 positive CD34 negative
    Actin negative Actin positive

    Spindle Cell Lipoma Sclerotic Lipoma
    Ropy bundles of collagen Diffuse collagen
    Usually has cellular areas Hypocellular
    CD34 extensive positivity CD34 negative to rare

    Spindle Cell Lipoma Atypical Spindle Cell Lipomatous Tumor
    Restricted to back of neck, upper back, shoulders Various locations
    Bland spindle cells Mild to moderate atypia of spindle cells
    Ropy collagen bundles No ropy collagen
    Circumscribed May be infiltrative
    Uniformly strong CD34 CD34 only 5% reactive
    Rb loss in all cases Rb normally expresed in 40$
    MDM2 and CDK4 negative to weak focal in 5% (FISH negative)

    Spindle Cell Lipoma Schwannoma or Neurofibroma
    S100 negative except for mature fat S100 positive
    Uniformly strong CD34 CD34 only scattered small spindle cells

    Spindle Cell Lipoma Solitary Fibrous Tumor
    Fat is integral part of lesion Fat only at infiltrative border
    May contain pleomorphic cells if admixed with pleomorphic lipoma No large pleomorphic cells
    Ropey collagen bundles Finely dispersed collagen
    Lacks staghorn vessels Frequent staghorn vessels

    Myxoid Liposarcoma Spindle Cell Lipoma with Myxoid Stroma
    Infrequent prominent spindle cell component Prominent spindle cell component
    Prominent "chicken wire" vascular pattern Lacks "chicken wire" vascular pattern
    No dense collagen bundles Dense collagen bundles
    Very rare in subcutis or dermis Usually in subcutis or dermis
    CD34 negative or scattered small cells CD34 widely positive
    t(12;16) or t(12;22) Frequent abnormalities of chromosomes 13 or 16

    Myxolipoma Spindle Cell Lipoma with Myxoid Stroma
    Lacks prominent spindle cell component Prominent spindle cell component
    May have prominent vascularity Vascularity rarely prominent
    No dense collagen bundles Dense ropy collagen bundles
    Location variable Largely restricted to back, shoulders, posterior neck

    Spindle Cell Lipoma Intramuscular or Juxta-articular Myxoma
    Cellular areas Uniformly paucicellular
    Superficial Deep
    May contain pleomorphic cells (admixed pleomorphic lipoma) Lacks large pleomorphic cells

    Spindle Cell Lipoma, Myxoid Predominant Superficial Angiomyxoma
    Usually has areas of typical spindle cell lipoma Lacks areas of typical spindle cell lipoma
    Parallel arrays of spindle cells in areas Randomly arranged cells
    Ropey collagen bundles Lacks ropey collagen
    Lacks neutrophils or entrapped adnexae Frequent neutrophils and entrapped adnexae


    • Approximately 1.4% of fatty neoplasms
    • Age range 20-74, most between 40-70
    • 90% male
    • Nearly all in subcutis of posterior neck, upper back or shoulders
      • Infrequent histologically identical tumors found in other sites
        • Must be pure spindle cell lipoma (no pleomorphism)
        • Must be located in dermis or submucosa
      • Histologically identical tumors in deep soft tissue are best considered atypical lipomatous tumors
        • Very little experience to permit prediction of behavior
    • Rarely familial or multiple

    Grading / Staging / Report

    • Grading and staging are not applicable
    • Mangerial category
      • Ia (Local excision is almost always curative; metastasis never occurs)


    Lipogenic tumors

    CD34 positive neoplasms (frequent and strong)


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