Bone and soft tissue sarcomas in cerebrospinal fluid and effusion: A 20-year review at our institution.

Background: The literature on bone and soft tissue sarcomas (BSTSs) involving effusions and cerebrospinal fluid (CSF) is very limited.

Methods: A computerized search for fluid cytology with a sarcoma diagnosis from 2000 to 2020 was performed. All available cases, including the clinical follow-up, were reviewed.

Results: A total of 57 fluids specimens from 36 BSTSs were identified (9 rhabdomyosarcomas, 6 angiosarcomas, 5 epithelioid hemangioendotheliomas, 3 dedifferentiated liposarcomas, 2 chondrosarcomas, 1 extraskeletal myxoid chondrosarcoma, 3 Ewing sarcomas, 2 undifferentiated sarcomas, 3 osteosarcomas, 1 synovial sarcoma, and 1 hybrid low-grade fibromyxoid sarcoma/sclerosing epithelioid fibrosarcoma). There were 22 males and 14 females. The age range was 4 to 82 years (median, 45 years). Sites of involvement included pleural fluid (n = 38), peritoneal fluid (n = 14), and CSF (n = 5). Twenty-four cytology cases were available for review. The cytologic features were nonspecific and ranged from dyshesive to clusters of round, epithelioid, pleomorphic, and occasionally spindle-shaped malignant cells that could easily mimic other non-BSTS malignant tumors. The diagnosis of BSTS was made by comparison with a prior specimen and/or ancillary studies (molecular or immunohistochemical stains). The prognosis was poor because 95% of the patients died of their disease.

Conclusions: The incidence of BSTS in fluid cytology is extremely rare, and it can have cytologic features similar to those of non-BSTS malignancies. Although, in most cases, a comparison with a prior known BSTS specimen may suffice, the use of ancillary studies is extremely helpful in arriving at the correct diagnosis. However, in cases with no known prior malignancy, including BSTS in the differential diagnosis is prudent for preventing misdiagnosis.