Spindle cell lesion


Spindle cell lesion is a term pathologists use to describe a group of spindle-shaped cells seen under the microscope. These cells are long and thin, often described as cigar-shaped or tapered at the ends, and are commonly found in connective tissues like muscle, fibrous tissue, and the lining of blood vessels.

This term is often used in biopsy reports, especially when only a small sample of tissue is available. It is a descriptive term, not a final diagnosis. More information, such as results from special tests or a larger surgical sample, may be needed to determine exactly what type of lesion or tumour is present.

Where are spindle cell lesions found?

Spindle cell lesions can be found in many parts of the body, including:

  • Skin and soft tissue.

  • Breast.

  • Lungs and pleura (lining around the lungs).

  • Digestive tract.

  • Genitourinary tract.

  • Head and neck.

Because spindle cells are a normal component of many tissues, spindle cell lesions can develop in a wide range of locations.

Are spindle cell lesions cancer?

Not all spindle cell lesions are cancer. The term simply describes how the cells look under the microscope. Spindle-shaped cells can appear in a variety of conditions, ranging from benign (non-cancerous) growths to malignant (cancerous) tumours.

This diagnosis is especially common in biopsy reports, where only a small portion of the lesion is sampled. In such cases, the pathologist may not have enough information to determine if the lesion is benign or malignant. A larger tissue sample or additional testing is often needed to reach a final diagnosis.

Spindle cell lesions generally fall into three main categories:

  • Benign (non-cancerous) tumours – These are slow-growing lesions made of spindle cells that do not invade surrounding tissue or spread to other parts of the body. Examples include:

    • Fibroma – a tumour of fibrous tissue.

    • Leiomyoma – a benign tumour of smooth muscle.

    • Schwannoma or neurofibroma – tumours that arise from nerve sheaths.

    • Nodular fasciitis – a benign, fast-growing lesion that can mimic cancer but is self-limiting.

  • Reactive or inflammatory conditions – In some cases, spindle cells appear in response to injury, infection, or chronic inflammation. These changes are not tumours but may still look abnormal under the microscope. Examples include scar tissue, granulation tissue, or postsurgical changes.

  • Malignant (cancerous) tumours – Some spindle cell lesions are cancers. These include:

Because spindle cell lesions have a broad range of possible causes, pathologists often need to perform special tests and may recommend examining more tissue to make a precise diagnosis.

How is the diagnosis made?

The initial diagnosis of a spindle cell lesion is usually made by examining a biopsy sample under the microscope. If the sample shows spindle-shaped cells, the pathologist may use additional tests to learn more about the type of lesion:

Immunohistochemistry

Immunohistochemistry is a special staining technique that uses antibodies to detect specific proteins in the cells. These stains help identify the type of cells present. For example:

  • Cytokeratins suggest the lesion may be a carcinoma.

  • S100 or SOX10 suggest melanoma or a nerve sheath tumour.

  • Desmin, myogenin, or MyoD1 support a muscle tumour.

  • SMA or MSA support a connective tissue muscle tumour.

  • CD34 or CD31 may indicate a vascular tumour.

  • CD117 (c-KIT) or DOG1 may point to a gastrointestinal stromal tumour (GIST).

Molecular testing

In some cases, genetic testing is done to look for specific mutations or rearrangements that help confirm the diagnosis. If the biopsy sample is too small or inconclusive, your doctor may recommend surgical removal or a larger biopsy to allow for a more accurate diagnosis.

What does spindle cell lesion mean for my treatment?

Because spindle cell lesion is a descriptive term, not a final diagnosis, the next steps will depend on what additional testing shows. In some cases, no further treatment is needed if the lesion is benign. In other cases, if cancer is suspected or confirmed, you may need surgery, chemotherapy, radiation, or a combination of treatments.

Your doctor will work closely with the pathologist to review the full report, including any special tests, and decide whether more tissue, further testing, or treatment is required.

Questions to ask your doctor

  • Was the spindle cell lesion found on a biopsy or surgical specimen?

  • Is the lesion benign, malignant, or do we need more information?

  • Were additional tests (like immunohistochemistry or molecular testing) performed?

  • Do I need more testing or a repeat biopsy to make a final diagnosis?

  • What are the next steps for diagnosis or treatment?

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