Fine needle aspiration cytology of primary soft tissue tumors. Morphologic analysis of the most frequent types.

We reviewed 98 cases of fine needle aspiration of soft tissue tumors with histologic confirmation performed during an eight-year period and propose a working morphologic classification based on the most prominent cytologic features. Six main tumor groups are recognized: myxoid, round cells, spindle cells, pleomorphic cells, polygonal cells and well differentiated. We believe that this classification allows recognition of the most common soft tissue tumors while helping with the differential diagnosis of other neoplasia, primary or secondary, with similar morphology and a similar presentation.

Fine needle aspiration in myxoid tumors of the soft tissues.

Myxoid tumors of soft tissues constitute a histogenetically heterogeneous group of lesions, both benign and malignant, that show an overproduction of mucopolysaccharide substances. A correlative fine needle aspiration (FNA) cytologic and histologic study was performed on 16 such cases (3 intramuscular myxomas, 2 lipoblastomas, 6 myxoid liposarcomas, 4 myxoid malignant fibrous histocytomas [MFHs] and 1 extraskeletal myxoid chondrosarcoma), with electron microscopic examination of the aspirate in 4 cases. FNA of all tumors produced a gelatinous material. Smears from all but one of the tumors had a granular myxoid background substance that stained blue to blue-red with the Diff-Quik stain; the exception was the extraskeletal myxoid chondrosarcoma, whose smears stained intensely blue-red to red. On light microscopy, only lipomatous tumors had distinctive cells with diagnostic value: the lipoblasts. Although the arrangement of lipoblasts in lipoblastomas differed somewhat from that found in myxoid liposarcomas, clinical data were important for making a definitive diagnosis. Intramuscular myxomas generally showed a low cellularity composed of fibroblastlike cells with no cytologic atypia. Myxoid MFHs were composed of fibroblastlike cells and macrophagelike cells; the elongated cells with slight-to-moderate nuclear atypia predominated in tumors of low-grade malignancy, while polygonal or round cells with one or more nuclei and marked nuclear atypia predominated in high-grade tumors. Although extraskeletal myxoid chondrosarcoma was mainly differentiated from low-grade myxoid MFH by its metachromatic matrix, ultrastructural studies showed the distinctive distended cisternae with microtubular aggregates in the extraskeletal myxoid chondrosarcoma, thus contributing to the definitive diagnosis.