Fibromyxoid tumour

A “fibromyxoid tumour” is not a specific diagnosis but a descriptive term that refers to various benign (noncancerous) or malignant (cancerous) tumours characterized by the presence of fibrous and myxoid tissue components. These tumours can arise in both soft tissues and bone throughout the body, and their behaviour depends on whether they are ultimately determined to be benign or malignant.

Types of fibromyxoid tumours

Fibromyxoid tumours are diverse in their presentation and behaviour. They can be broadly categorized into those arising in soft tissue and those arising in bone, each with unique characteristics and implications for treatment and prognosis.

Fibromyxoid tumours arising in soft tissue

• Low grade fibromyxoid sarcoma (LGFMS): LGFMS is a rare type of cancer that typically occurs in the deep soft tissues of the trunk, arms, and legs. It’s known for its slow growth but has a potential for recurrence and metastasis.
• Myxofibrosarcoma: This cancerous tumour more commonly occurs in older adults. It usually appears in the limbs and is known for its variable aggressiveness and high recurrence rate.
• Ossifying fibromyxoid tumour: This tumour often presents as a painless, enlarging mass. It is characterized by its fibromyxoid stroma and an ossified periphery. Most are noncancerous but cancerous types can occur.
• Desmoid-type fibromatosis: A noncancerous but locally aggressive tumour that shows fibrous and sometimes myxoid features, primarily arising in muscles and connective tissue.
• Solitary fibrous tumour: Found in various anatomic locations, these tumours can occasionally exhibit myxoid characteristics amid their predominantly fibrous matrix. Most behave in a noncancerous manner, but cancerous entities do occur.
• Intramuscular myxoma: A benign, purely myxoid tumour that occurs within muscle tissue.
• Spindle cell lipoma: Typically found in the subcutaneous tissues of the neck, shoulders, and back, these benign tumours may exhibit myxoid changes.

Fibromyxoid tumours arising in bone

• Fibromyxoma: This benign tumour primarily arises in the jawbone (mandible or maxilla) but can appear in other bones. It features a mix of fibrous and myxoid tissue, with a generally slow growth pattern and low potential for aggression.

Additional diagnostic tests

The term fibromyxoid tumour is a preliminary diagnosis, and a combination of tests are typically employed to help refine the diagnosis further and potentially reach a more definitive and final diagnosis. These tests include:

• Imaging tests: MRI and CT scans can help define the origin of the tumour (for example, soft tissue versus bone) and its relationship with surrounding tissues.
• Pathological examination: A biopsy is essential for analyzing the cellular characteristics of the tumour. The presence of cellular atypia, mitotic activity, and necrosis helps distinguish between benign and malignant tumours.
• Immunohistochemistry (IHC): This test uses antibodies to detect specific antigens in the tumour cells, helping to differentiate between different types of fibromyxoid tumours. For example, LGFMS often shows positivity for MUC4, a diagnostic marker not typically found in other soft tissue tumours.
• Genetic tests: Genetic testing such as next-generation sequencing (NGS) can identify specific chromosomal translocations or mutations. LGFMS, for instance, is often associated with a fusion gene created from a translocation between chromosomes 7 and 16.
• Fluorescence in situ hybridization (FISH): This test can detect specific genetic abnormalities in the cells, such as translocations, that are often associated with certain types of tumours.

About this article

Doctors wrote this article to help you read and understand your pathology report. Contact us if you have any questions about this article or your pathology report. Read this article for a more general introduction to the parts of a typical pathology report.

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Atlas of Pathology