Year : 2008 | Volume
: 25 | Issue : 3 | Page : 87--88
Cytology of soft tissue tumors: Malignant spindle cell tumors
Department of Pathology, Nizam's Institute of Medical Sciences, Punjagutta, Hyderabad - 500 082, India
Department of Pathology, Nizam«SQ»s Institute of Medical Sciences, Punjagutta, Hyderabad
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Prayaga A. Cytology of soft tissue tumors: Malignant spindle cell tumors.J Cytol 2008;25:87-88
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Prayaga A. Cytology of soft tissue tumors: Malignant spindle cell tumors. J Cytol [serial online] 2008 [cited 2020 Jul 12 ];25:87-88
Available from: http://www.jcytol.org/text.asp?2008/25/3/87/44036
Cytological diagnosis of spindle cell tumors is fraught with the greatest diagnostic difficulty and the greatest potential for false positive and false negative diagnoses compared to other soft tissue tumors due to the difficulty in distinguishing benign and low-grade tumors. Hence, the diagnosis of a spindle cell tumor should follow after careful exclusion of benign lesions. The role of cytology in malignant spindle cell tumors is to initially diagnose them as malignant spindle cells and subsequently, to subtype them. The diagnosis of malignancy is based on the cellularity and the presence of single cells, and the cytological features of malignancy, namely, hyperchromasia in almost all the cells. The presence of atypical mitotic figures is a very useful feature in cytodiagnosis. On the other end of the spectrum, neither the nuclear nor the cytoplasmic features help in distinguishing high-grade tumors. Following is a list of malignant spindle cell tumors. Lesions that can resemble spindle cell sarcomas include ancient schwannoma, nodular fasciitis, and postoperative spindle cell nodules.
Cytological features and differential diagnoses of spindle cell sarcomas: ,,,,
Fibrosarcoma: Seen in young adults; locations are usually the head and neck, lower extremities, and the trunk. Cytological features include highly cellular smears with spindle cells in bundles. Nuclei are round to oval and the cells are vesicular with a moderate amount of tapering cytoplasm. Mitotic figures may be abundant and high-grade tumours show single cells with obvious cytological evidence of malignancy. They may be difficult to classify beyond spindle cell sarcomas, hence, the diagnosis is by exclusion. Immunocytochemistry with vimentin, electron microscopic demonstration of basal lamina, RER, collagen, and cytogenetic abnormalities of +8, +11, +17, +20 are ancillary techniques useful for the diagnosis.
Leiomyosarcoma: These tumours are usually seen in adult patients in the abdomen or the pelvis. Cytological features are moderate to scant cellularity, nuclei may be uniform or pleomorphic, cigar-shaped with abundant acidophilic or cyanophilic cytoplasm, and characteristic perinuclear vacuoles.
Ancillary techniques include immunochemistry with desmin, muscle-specific actin, electron microscopy for basal lamina, myofilaments and dense bodies, and cytogenetic abnormality of deletion of 1p.
Synovial sarcoma: These tumours are found usually in young patients, near the joints. Cytological features include short, uniform spindle or epithelial cells with uniform vesicular nuclei and micronucleoli. Gland formation in biphasic lesions is a useful diagnostic feature. Immunochemistry with keratin, vimentin, and CEA are useful. Lumina, microvilli, and cell junctions can be seen with the aid of electron microscopy. A cytogenetic hallmark is t(X;18) (p 11;q11) and the molecular marker is fusion of SYT-SSX .
Malignant Peripheral Nerve Sheath Tumours
They are usually seen in the setting of von Recklinghausen's disease. The smears are cellular; cells may be single or in fascicles. Nuclei are pleomorphic and mitotic activity is present. Nuclei are wavy with long fibrillary cytoplasm; stroma is delicate and fibrillary and S-100 is variable. Ultrastructurally, basal lamina, microfilaments, and microtubules can be found.
Vascular tumors: These are rare tumors that include hemangio-endothelioma, hemangiopericytoma, angiosarcoma, lymphangiosarcoma, and Kaposi's sarcoma. These tumors usually have low cellularity. Poorly differentiated tumors are more cellular with the cytological features of malignancy. A capillary network is seen with atypical endothelial cells and cytoplasmic lumina may be seen. Immunochemistry with factor VIII, Ulex, CD31, CD 34 can help in the diagnosis. Useful ultrastructural features are the presence of Wiebel-Palade bodies, pinocytic vesicles, basal lamina, and tight junctions.
Spindle cell squamous cell carcinoma and melanoma can resemble soft tissue sarcomas. Squamous differentiation with irregular, ink-dot-like and keratin positivity, ultrastructural findings of desmosomes, tonofilaments for the former, melanin, and HMB-45 positivity for the latter are helpful.
Grading of Spindle Cell Sarcomas
Considering the difficulties involved in the typing of soft tissue sarcomas, grading is suggested as it can have bearing on their management and prognosis. , Based on nuclear atypia, nuclear overlap, mitotic figures, and necrosis, the tumors are grouped into grades 1, 2, and 3. Nuclear atypia is graded as mild, moderate, and severe based on nuclear variation, nuclear contour, chromatin, and the nucleoli. 
However, caution should be exercised while grading as some of the reactive spindle cell proliferations show pleomorphism and some high-grade tumors can have low cytologic grades.
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