What is a spindle cell neoplasm?

A spindle cell neoplasm is a tumour made up of spindle-shaped cells, which are cells that are longer than they are wide. Under the microscope, these cells look like elongated ovals or grains of rice. The term spindle cell neoplasm describes how the cells look, not the exact type of tumour. Many different tumours contain spindle-shaped cells, some benign (non-cancerous) and others malignant (cancerous).

Pathologists often use this term when the initial tissue sample does not provide enough information for a more specific diagnosis. Additional tests are usually performed to determine the exact type of tumour present.

Why might my pathology report use this term?

Your pathology report may use the general term spindle cell neoplasm after an initial biopsy, especially if the sample is small or shows overlapping features shared by many tumour types. This descriptive term allows your healthcare team to continue evaluating the tumour while special stains or molecular tests are completed.

Are all spindle cell neoplasms cancerous?

No. Spindle cell neoplasms range from benign tumours that do not spread to aggressive cancers that require specialized treatment. Determining whether a tumour is benign or malignant requires microscopic examination and often additional tests such as immunohistochemistry, fluorescence in situ hybridization (FISH), or next-generation sequencing (NGS).

Examples of benign spindle cell neoplasms

Benign spindle cell tumours do not spread to other parts of the body, although some may grow back in the same place after removal.

Schwannoma

A tumour that develops from the cells surrounding nerves. It is slow-growing and usually causes symptoms only if it presses on a nearby nerve.

Neurofibroma

A benign tumour made of nerve-related tissue. It is often soft and painless and can appear as a single growth or as multiple tumours in people with neurofibromatosis type 1.

Solitary fibrous tumour

A tumour that can develop almost anywhere in the body. Most solitary fibrous tumours are benign, although some can behave more aggressively.

Spindle cell lipoma

A tumour made of fat and spindle cells. It most commonly occurs on the back or neck of adults and grows slowly.

Leiomyoma

A tumour of smooth muscle, most commonly seen in the uterus (“fibroids”), digestive tract, or skin. Leiomyomas are benign and often cause no symptoms.

Fibromatosis

A benign but locally aggressive growth of fibrous tissue. It does not spread to distant organs but may grow back after surgery, and sometimes it infiltrates surrounding tissue.

Examples of malignant spindle cell neoplasms

Malignant spindle cell neoplasms include many types of sarcomas, which are cancers that arise from connective tissue such as muscle, fat, bone, blood vessels, or nerves. These tumours can spread to other parts of the body and often require specialized treatment.

Malignant peripheral nerve sheath tumour (MPNST)

A cancer that develops from the cells around nerves. It is more common in people with neurofibromatosis type 1 and tends to grow quickly.

Dermatofibrosarcoma protuberans (DFSP)

A slow-growing skin cancer that starts in the deeper layers of the skin. It rarely spreads but often regrows unless completely removed.

Liposarcoma

A malignant tumour that forms from fat cells. It often occurs in the thigh or abdomen and can behave differently depending on the tumour subtype.

Osteosarcoma

A cancer that produces bone tissue. It typically affects children and young adults and often begins in the arms or legs.

Leiomyosarcoma

A cancer of smooth muscle, which is found in places like the uterus, digestive tract, and blood vessel walls. It tends to behave aggressively.

Angiosarcoma

A cancer that arises from blood vessel cells. It can occur anywhere in the body and often grows and spreads quickly.

Synovial sarcoma

A cancer that usually develops near joints such as the knee or ankle. Despite its name, it does not come from the synovial lining but has a distinctive genetic change.

Undifferentiated pleomorphic sarcoma

A high-grade sarcoma made of very abnormal-appearing cells. It often occurs in the arms or legs of older adults and grows quickly.

Spindle cell melanoma

A type of melanoma in which the cancer cells take on a spindle shape. It can resemble a sarcoma under the microscope but behaves like melanoma.

Spindle cell squamous cell carcinoma

A form of squamous cell carcinoma in which the cells appear spindle-shaped. It can arise in the skin, lungs, head and neck, or digestive tract.

How do pathologists determine the exact diagnosis?

Pathologists combine several types of information to classify a spindle cell neoplasm:

• The microscopic appearance, including how the cells are arranged and whether they invade nearby tissue.

• Results of immunohistochemical staining, which detect proteins that help identify the cell type.

• Molecular testing, which looks for specific mutations or gene rearrangements.

• Clinical information, including the tumour’s size, location, and imaging results.

A final diagnosis often requires integrating all of these findings.

Why is identifying the specific tumour type necessary?

Different spindle cell tumours behave differently. Some require only observation or simple surgery, while others require chemotherapy, radiation therapy, or targeted therapy. A precise diagnosis helps your healthcare team:

• Understand how the tumour is likely to behave.

• Choose the most effective treatment.

• Estimate prognosis.

• Decide whether additional testing or monitoring is needed.

Questions to ask your doctor

• What type of spindle cell tumour do I have?

• Is the tumour benign or malignant?

• What special tests were performed to confirm the diagnosis?

• Do I need additional imaging or biopsy?

• What treatment options are recommended?

• What is the expected behaviour of this tumour?

• Should I be monitored for recurrence?