Fine-needle aspiration biopsy of soft tissue sarcomas. A cytomorphologic analysis with emphasis on histologic subtyping, grading, and therapeutic significance.

Because therapy for sarcoma often incorporates histologic subtype, grade, stage, and anatomic location, establishing a specific histologic subtype often is essential. To evaluate the effectiveness of fine-needle aspiration biopsy (FNAB) in histologic subtyping of soft tissue sarcomas, we retrospectively reviewed 73 consecutive aspirates from 67 patients, none of whom had a previously established sarcoma diagnosis. Sarcoma cases were subgrouped according to predominant cytomorphologic features: pleomorphic cell, 19; small round cell, 18; spindle cell, 18; myxoid, 10; epithelioid/polygonal cell, 7; 1 case of well-differentiated liposarcoma was analyzed separately. Ancillary studies were used for 25 cases. Among adequate specimens, 61 tumors were recognized as sarcoma. A specific and accurate histologic subtype was determined in 34 cases. Ancillary studies were most useful for histologic subtyping of small round cell and spindle cell sarcomas. Myxoid sarcomas were subtyped easily based solely on histomorphologic features. Pleomorphic cell and epithelioid/polygonal cell sarcomas were recognized easily as malignant but difficult to subtype by FNAB. With the exception of small round cell sarcomas, histologic subtyping of a sarcoma usually did not directly influence therapy. With meticulous attention to clinicopathologic features and ancillary techniques, many sarcomas, especially small round cell, spindle cell, and myxoid types, may be subtyped successfully by FNAB, within limitations.