IAP 2006 Symposium #03 - Fine Needle Aspiration Cytopathology: Bone and Soft Tissue

Diagnosis	Clinical features	Cytologic features
Neurilemoma [9, 10]	Predominantly a tumor of adults but can occur in children. Variable location and size. Can be cystic. Often painful at aspiration. Usually a long clinical history.	Variable yield. Mixture of fascicles or dissociated spindled cells with moderate nuclear pleomorphism. Usually admixture of rounded/ovoid cells. Common features are variable cellularity in the fascicles with appearance similar to histological Antoni A and Antoni B features, elongated nuclei with pointed ends occasionally having a "fish-hook" appearance and a fibrillar background. Occasional palisading of nuclei. Rare Verocay bodies.
Nodular fascitis [11]	A rapidly growing, occasionally tender mass showing a predilection for upper extremities in young adults. Usually superficial and less than 3.0 cm. Majority of NF regress spontaneously within 3-6 weeks.	Rich yield. Moderate pleomorphic spindle, triangular or rounded cells. Nuclei have bland chromatin, often prominent nucleoli and occasional mitoses. Myxoid background and ganglion-like cells frequently present. Occasionally multinucleated cells or/and inflammatory cells. Late fasciitis often shows more uniform spindled cells than fasciitis in the growing phase.
Solitary fibrous tumor [3] (Extrapleural)	Deep-seated soft tissue tumor of adults seen in various locations. Often slow- growing.	Rich to moderate yield. Uniform spindle cells having scanty uni- or bipolar cytoplasm. Cells are dissociated or arranged in fascicles in a haphazard or, occasionally, a storiform pattern. Stripped nuclei and collagen matrix fragments in background.
Spindle cell lipoma [12]	Small or medium-sized, subcutaneous mass, typically localized in the neck, back or shoulder of middle-aged men. Long clinical history.	Variable yield. Strands of uniform spindled cells, adipose tissue and collagen bundles/fibers in variable proportions. Long, slender, acellular collagen fibers are common. Often a myxoid background with mast cells.
Desmoid fibromatosis [13]	Infiltrative masses in the deep soft tissues. Usually in the proximal extremities or limb girdles of young adults. Often larger than 5.0 cm.	Variable yield. Spindled cells, either dissociated or in clusters, with indistinct cytoplasm and cytoplasmic processes. Uniform, spindled or fusiform nuclei, sometimes with moderate anisokaryosis. Stripped nuclei and fragments of more or less cellular collagenous tissue common. Occasional striated-muscle "giant cells".
Elastofibroma dorsi [5]	Typically located near the inferior margin of the scapula or between the scapula and the chest wall in elderly women.	Poor to moderate yield. Mixture of uniform spindle cells, mature adipocytes and fragments of acellular collagen bundles and fibres in varying proportions. In alcohol fixed smears degenerated elastic fibres with linear ("braid-like"), globular and stellate appearances.
Hemangio-Pericytoma [3, 14]	A rare soft tissue tumor, most often localized in the deep soft tissues and retroperitoneum.	Variable yield. Irregular clusters of cohesive cells mixed with dispersed cells. Often stripped nuclei. Branching vessels are seen as stalks in the middle of cell clusters. Slightly atypical spindle cells with elongated cytoplasm. Synovial sarcoma with hemangiopericyte-like pattern must be excluded.
Synovial sarcoma [15, 16]	Can occur at almost any age and in any site. Often long clinical history.	Rich yield. Mixture of tight sheets or clusters and dispersed small to medium sized, often bland-looking cells with spindle/ovoid or rounded nuclei and scanty unipolar or bipolar cytoplasm. Nucleoli are inconspicuous and chromatin finely granular. Capillary vessels within cell-clusters and mast cells usually present. Storiform pattern and a myxoid matrix may be seen. The infrequent subcutaneous monophasic synovial sarcoma can mimic DFSP.
Leiomyosarcoma [7, 17, 18]	Occur predominantly in adults. Most common locations: retroperitoneum and limbs, both subcutaneously and deeply seated.	Moderate to rich yield. Tumor cell fascicles with an admixture of dispersed cells or stripped nuclei. Spindle cells with elongated, blunt-ended, segmented or fusiform nuclei and round/polygonal cells, often with rounded or indented nuclei. In high-grade LMS often pleomorphic, multinucleated cells and intranuclear vacuoles.
Malignant peripheral nerve sheath tumor [19, 20]	Occur usually in adults, may occur in children Upper extremities, thigh, buttock and paraspinal tissues are common sites.	Moderate to rich yield. Mixture of dispersed cells and cells in tight cluster or fascicles. Variably atypical spindle cells. Typically elongated nuclei with pointed ends. In high grade malignant MPNST marked pleomorphism. Variable diagnostic help with immunocytochemistry. Low grade variants difficult to diagnose correctly in FNA.
Dermatofibro-sarcoma protuberans [21, 22, 23, 24]	Occur usually in young and middle-aged adults. Slowly growing involving dermis, subcutis, rarely deep soft tissue in the trunk, abdomen, proximal extremities and head.	Moderate to rich yield. Compact, thick clusters of spindle cells with an admixture of small sheets of spindle cells as well as numerous dissociated cells or naked nuclei. Relatively uniform spindle to oval nuclei with finely dispersed chromatin and inconspicuous nucleoli. Occasionally storiform pattern and spindle cells embedded in a collagenous/fibrillar matrix.
Adult fibrosarcoma	Uncommon sarcoma arising in the deep soft tissues in extremities and head and neck region.	Mixture of dispersed cells and cell clusters. Variably atypical spindle cells. Marked atypia in high grade malignant tumors. Insufficiently characterised in FNA.
Low grade Fibromyxoid sarcoma [25]	Young adults but described in children. Uncommon sarcoma, typically in the extremities or trunk.	Variable yield, variable prominent myxoid matrix. Slightly atypical spindly or ovoid cells. Difficult to distinguish from benign myxoid/spindle tumors such as soft tissue perineurioma. Insufficiently described in FNA.