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The value of electron microscopy as an adjunct to fine needle aspiration cytology in the preoperative diagnosis of soft tissue tumors was studied in 22 cases. In 19 of these, the aspirated material obtained was adequate for electron microscopy analysis. The aspiration procedure did not damage the cells, and the aspirates were well suited to electron microscopic examination. In many cases this examination enhanced the precision of diagnosis and subclassification. This was the case in two intramuscular myxomas diagnosed as myxoid liposarcomas with light microscopy and in two sarcomalike squamous cell carcinomas diagnosed as polymorphous sarcomas in the ordinary smears.

Nodular fasciitis, the most common pseudosarcomatous proliferative lesion of the soft tissues, is well defined histologically but not cytomorphologically. A histologic and cytologic study of 13 cases of nodular fasciitis is presented. Nodular fasciitis is characterized histologically by proliferating fibroblastlike cells that vary from thin, elongated and spindle shaped with elongated nuclei to plump with one or more large, oval nuclei. The appearance of nodular fasciitis in fine needle aspirations is characterized by the presence of tumor cells varying widely from spindle shaped with long cytoplasmic processes to more plump and cytoplasmatic with one or more nuclei with nucleoli. An attempt to correlate the histologic and cytologic appearances is made. It is stressed that all the cells in nodular fasciitis lack histologic and cytologic signs of malignancy. The differential diagnosis is discussed. The cytomorphology of nodular fasciitis is fairly characteristic, making it possible to recognize these lesions in fine needle aspirates.

A case is reported in which electron microscopy was utilized to make a preoperative differential diagnosis of a soft tissue sarcoma on material obtained by fine-needle aspiration biopsy. The value of electron microscopy as an adjunct to cytologic study of such material is pointed out, as is the suitability of aspirated material for electron microscopic examination.

A study of the preoperative fine needle aspiration cytologies in consecutive patients with primary malignant tumors (203 cases) or benign thyroid tumors (217 cases) showed a sensitivity of 0.57 and a specificity of 0.98. The sensitivity of FNA cytology in medullary and undifferentiated carcinomas was 0.82 and 0.84, respectively; none of these were microscopically misdiagnosed. The sensitivity was only 0.58 for papillary carcinomas (excluding occult carcinoma) and 0.42 for follicular carcinoma. Four reasons for these low sensitivities were identified: tumors missed at aspiration, microscopic misinterpretations, diagnoses of cellular atypia and indeterminate diagnoses. Reevaluation of the false diagnoses once more emphasized the problem of distinguishing follicular adenomas from follicular carcinomas. Microscopically undiagnosed papillary carcinomas were either the result of misinterpretations of the characteristic cytomorphologic features or of the smears being misdiagnosed as showing cellular atypia when papillary formations were missing and only one or two of the other cellular criteria were evident. The specificity of FNA cytology of thyroid tumors was found to be high enough to permit surgical intervention after a cytodiagnosis of malignancy.

An 89-year-old female with a two-year history of a growing tumor of the skin on her left thigh was subjected to fine needle aspiration. Cytologic examination of the aspirate revealed a small-cell carcinoma, and a Merkel-cell carcinoma was suggested. The diagnosis was confirmed by histopathologic and electron microscopic analysis of the removed tumor. The cytologic findings are presented and correlated with the light and electron microscopic pictures of the operative specimen.

Soft-tissue tumors are a fairly new area for aspiration cytology. As part of the correlation between the cytology and histology in these tumors, a retrospective study of ten intramuscular myxomas was conducted. All of the patients presented with a firm, painless intramuscular mass that was excised with different surgical margins; no recurrences were found at follow-up. The cytologic findings corresponded well with the histologic ones. Droplets of a highly viscous fluid typically characterized an aspirate from an intramuscular myxoma. The fluid was generally not very cellular. The cells had elongated cytoplasm and spindle-shaped nuclei. They varied in size and shape, and cellular atypia was minimal. Aspirates from low-grade myxofibrosarcoma and myxoid liposarcoma presented the main differential diagnostic problems.