Synovial Sarcoma Metastasized to the Brain

Introduction

Synovial sarcoma is a distinct mesenchymal spindle cell tumor, which displays variable epithelial differentiation and has a characteristic chromosomal translocation t(X; 18) (p11; q11). It can rarely metastasize to the brain.

Brain Synovial Sarcomas

By searching Pubmed for synovial sarcoma and brain, we could find 38 references.

Nine of them described nine cases of brain synovial sarcoma. One of these patients was the same in two papers, thus leaving eight patients. Three cases were described as primary brain synovial sarcoma. They were dura based. All were treated surgically ( ). Another five cases were described as metastases: one of them was treated surgically, due to cerebral hemorrhage ( ), one with biopsy and conservative treatment and three conservatively ( ).

Another 33 cases of synovial sarcoma of the brain were found by looking at the references of the previous articles and mainly by using the first 200 references of Google Scholar for synovial sarcoma and brain. These patients were usually described as part of large series of synovial sarcomas, soft tissue sarcomas or sarcomas in general. Their description was consequently not as detailed as in the previous cases. One of these patients has a dural-based primary synovial sarcoma of the brain.

All these 41 patients were the material of our present paper. We could not find any systematic review of brain synovial sarcoma in the literature.

In order to classify properly brain synovial sarcoma, we must first review synovial sarcoma in general.

Synovial Sarcoma

Epidemiology

Synovial sarcomas constitute ≈8% of soft tissue sarcomas. They can occur at any age, but almost 90% occur in young adults before the age of 50 and most between the ages of 15 and 35 years. There is a slight male preponderance (ratio ≈1.2:1).

Clinical Features

There is usually a mass of 3–10 cm, with or without pain. Location is mainly 71% in the lower and 16% in the upper extremities ( ). Local symptoms in specific sites can also be observed. Growth is often slow, with a mean history of 2–4 years; 20-year histories have been described. Within the soft tissues, the neoplasm is typically situated in deeper structures, such as tendon or muscle rather than the subcutis. General symptoms related to malignancies can be reported, such as fatigue. At the time of diagnosis, ≈10% of cases present with metastases.

The natural course of the disease is such that many patients will experience recurrence of the primary tumor and/or metastatic disease. Up to 50% can recur locally. Metastatic disease occurs in around 50% of patients. The most common sites of metastasis are the lungs, occurring in 74–81% of patients with metastatic disease, lymph nodes, occurring in 3–23%, and bone, occurring in 10–20%.

Among the different grading systems available, the French system, FNCLCC (French Federation of Cancer Centers Sarcoma Group), is the most often used for adult-type soft tissue sarcomas ( ). It is a score system in which the sum of D (differentiation; ‘D3’ by default in synovial sarcoma), M (mitoses: below 10/10 high power fields (HPF); between 10 and 19/10 HPF; more than 19/10 HPF) and N (necrosis: absent; less than 50%; more than 50%) gives the grade 1, 2 or 3. Even if in therapeutic protocols synovial sarcoma is considered among high-grade sarcomas by definition, the FNCLCC grade is reported as its most predictive histological factor. The NCI grading system is more common in the USA ( ).

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