Synovial sarcoma (SS) is a high-grade malignant soft tissue tumor that manifests different phenotypic subtypes that may render their cytologic evaluation challenging. Although several cytologic studies of SS have been published, correlative studies of cytologic and corresponding histologic features are limited. To better define the cytological features of various SS forms, we reviewed the cytologic and the corresponding histologic material of 56 tumors from 36 patients. Classical patterns were defined as dispersed or small clusters of cells with bland chromatin, inconspicuous nucleoli, oval to spindle-shaped cytoplasm and branching tumor tissue fragments, vessel stalks, acinar structures in scant mucin background, seen in all 53 (94.7%) cellular cases. Epithelial, squamous, round cells, mast cells, necrosis, comma-like nuclei, marked nuclear atypia, secretory mucin, and rosette-like structures were also occasionally observed. Comparing the histological subtype we noted that epithelial cells and secretory mucin were restricted to biphasic SS, round cells to poorly differentiated SS, and comma-like nuclei to monophasic fibrous SS. We conclude that the classical pattern is highly suggestive of SS of all three monophasic, biphasic, or poorly differentiated subtypes. These characteristics, along with molecular genetic studies, may improve the cytologic diagnosis of SS.

To characterize the cytological features of angiosarcomas, we reviewed the fine-needle aspiration material and corresponding histologic sections of 29 tumors in 23 patients. Histologically, 24 tumors were of the classic type, and 5 were epithelioid angiosarcomas. The original corresponding cytologic diagnoses were as follows: angiosarcoma, 17 cases; sarcoma not otherwise specified, 8 cases; and rhabdomyosarcoma, 1 case. Three samples were cell-poor and were considered suspicious of malignancy. The review of cytology samples showed that smears were cell-rich in 17 tumors and cell-poor in 12 tumors. A hemorrhagic background was present in 9 cases. Tumor cells were polymorphous, including spindle-shaped, round to oval, and polygonal epithelioid cells and giant cells in different proportions. Erythrophagocytosis was seen in 12 tumors. Smears of classic angiosarcomas were polymorphous and lacking specific characteristics, whereas smears of epithelioid tumors were morphologically similar and composed of round to oval and polygonal, epithelial cells frequently arranged in clusters, and showing erythrophagocytosis. The wide spectrum of cellular components of angiosarcomas accounts for the difficulty in establishing accurate tumor typing, particularly with cell-poor samples and low-grade classic angiosarcoma. Entities to consider in the differential diagnosis are carcinoma, epithelioid sarcoma, pleomorphic rhabdomyosarcoma, and malignant melanoma.

Cytomorphological patterns of malignant peripheral nerve sheath tumor (MPNST) are insufficiently documented in the literature. Cytological and histological specimens in 24 tumors in 17 patients were correlated. The review of the original cytology reports showed that four (16.6%) tumors were correctly diagnosed, eight (33.3%) were diagnosed as sarcoma not otherwise specified, four (16.7%) as fibrosarcoma, three (12.5%) as synovial sarcoma, three (12.5%) as leiomyosarcoma, and one (4.2%) case each as malignant fibrous histiocytoma and rhabdomyosarcoma. At the review tumors were histologically reclassified as well-differentiated MPNST in 11 (45.9%) cases, anaplastic MPNST in 11 (45.9%) cases, and epithelioid MPNST and malignant Triton tumor in one (4.2%) case each. Cytologically, well-differentiated MPNST were composed of polymorphous oval to round cells, small spindle-shaped cells with wavy and comma-like naked nuclei, and a fibrillary, delicate stroma. Anaplastic MPNST, moreover, were composed of anaplastic giant and polymorphous cells. The malignant Triton tumor was composed of oval to round rhabdomyoblastic cells with eccentric nuclei and the epithelioid MPNST of polymorphous and round, epithelial-like cells. The cytological diagnosis of MPNST may be difficult, especially in anaplastic tumors. The correlation between the cytological features and the clinical information--origin of the tumor from a nerve trunk, a preexisting neurofibroma, patients with known history of neurofibromatosis 1--could be indicative of an MPNST diagnosis.

Fine-needle aspiration (FNA) followed by a core-needle biopsy during general anesthesia is a method for diagnosing pediatric tumors in our Institute. To complete the diagnosis in the case of round cell sarcomas, cytology material is also used for genomic analyses, that is, karyotyping and molecular biology-derived techniques. Fifty primary Ewing sarcomas/peripheral neuroectodermal tumors (ES/PNET) in 50 patients were sampled. Cytological diagnoses were "malignant" in all cases and accurate (ES/PNET) in 46 (92%). Two (4%) cases were misdiagnosed as neuroblastoma, and two others (4%) as rhabdomyosarcoma and nephroblastoma. No suspicious or false-negative results were rendered. Karyotyping was performed in 20 (40%) cases and was interpretable in 17 cases but not in three cases. Molecular search for ES/PNET fusion transcripts were performed in all cases and were detected in 44 (88%) cases, but not in six (12%) cases. In conclusion, FNA assisted by genomic techniques is powerful methods to accurate diagnose ES/PNET.