Soft tissue aspiration cytopathology

Fine-needle aspiration (FNA) biopsy as a diagnostic modality for the pathologic evaluation of soft tissue neoplasms and non-neoplastic soft tissue mass lesions is uncommon and controversial. This procedure contrasts with more traditional diagnostic methods such as marginal excision, incisional (open) biopsy, or even core biopsy to procure tissue from somatic sites.

The authors reviewed the results of cytopathologic diagnoses obtained by fine-needle aspiration biopsy over a consecutive 11-month period in patients that presented primarily with a palpable soft tissue mass. A few patients with deep non-palpable soft tissue masses also were evaluated by radiologically guided FNA. Cytopathologic diagnoses were verified by different means including tissue examination either by concurrent cell block or subsequent surgical biopsy, flow cytometry, clinical outcome, or repetition of the FNA procedure. Patients were followed for a minimum of one year to evaluate the mass clinically, to determine whether any further therapy was administered, and to assess disease status.

Eighty-two aspirates were performed without complications from 77 patients ranging from 12-88 years of age (mean = 50 yrs.) with men outnumbering women 1.5:1. Soft tissue masses were most common in the extremities (41 cases), followed by the trunk (34 cases), retroperitoneum (5 cases), and head and neck (2 cases). Fine-needle aspirates were diagnosed as malignant in 42 (51%), benign in 32 (39%), nondiagnostic in 6 (7%), and atypical in 2 (2%) cases. Malignant aspirates were comprised of 24 sarcomas (57%), 9 carcinomas (21%), 6 malignant lymphomas (14%), and 3 melanomas (7%). Twenty-two aspirates (52%) had an initial diagnosis of malignancy, whereas 18 (43%) represented metastatic and 2 (5%) recurrent neoplasms. Confirmation of the cytopathologic diagnosis was by concurrent or subsequent tissue examination in 57%, flow cytometry in 5%, clinical outcome in 34%, and repeat aspiration in 4%. One false negative and no false positive diagnoses were issued for a sensitivity and specificity of 100% and 97% respectively in distinguishing benign and malignant lesions by FNA. Of the malignant aspirates, 83% could be subtyped whereas 72% of benign aspirates were correctly subtyped. For primary soft tissue sarcomas, 12 of 19 (63%) were accurately subtyped. In 48% of cases a concurrent cell block was obtained and found diagnostically useful in 54% of them.

Aspiration cytopathology of soft tissue mass lesions using FNA biopsy can be an accurate and minimally invasive method for the initial pathologic diagnosis of primary benign and malignant soft tissue masses, for the pathologic confirmation of metastatic tumors to soft tissue, and for the documentation of locally recurrent soft tissue neoplasms. FNA cytopathology is capable of specifically subtyping a large percentage of primary and metastatic soft tissue tumors if cellular material either in the form of a cell block or flow cytometry is obtained in addition to cell smears.