PMC3977165_01
A) Magnetic resonance imaging thigh showing extraskeletal origin of tumor with no zonal pattern; B) fine needle aspiration smears showing small round cells with matrix (Inset, 400x); C) fine needle aspiration smears showing cytoplasmic vacuolization in small round cells (1000x); D) Gross: infiltrating grey white firm growth with areas of cystic degeneration.
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MRI showed a variegated mixed intensity lesion in antero-medial aspect of left thigh arborizing left adductor, obturator, pectineus, vasti and fringe of sartorius and ilio-psoas musculature and enclosing neuro-vascular bundles with cystic degeneration, necrosis and associated solid density lesional matrix and discrete calcific foci (Figure 1A). Patient was referred for fine needle aspiration cytology (FNAC) of lesion and smears showed diffuse sheets of small round cells with mild pleomorphism, high nuclear cytoplasmic ratio (N:C ratio) and dark fine granular chromatin without classical rosseting pattern with few foamy histiocytes and scant osteoid (Figure 1B, 1C). Focal gritty areas were observed (Figure 1D).
A) Small round cells surrounding malignant fine osteoid and mineralized osteoid (Inset, 400x); B) small round cells surrounding malignant fine osteoid (100x) with trichrome stain highlighting osteoid (Inset, 400x); C) small round cells in nesting pattern with PAS positivity (400x); D) negative S100 stain in tumor cells as well as in matrix with paucireticular pattern (Inset, 400x).
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Microscopy showed nodules and islands of tumor with focal malignant lace like as well trabecular mineralized and non-mineralized osteoid formation without any cartilage or zoning pattern (Figure 2A). Trichrome stain highlighted neoplastic osteoid (Figure 2B). Tumor cells were small, round with inconspicuous cytoplasm, dense coarse chromatin with minimal pleomorphism with 1-2 mitosis/hpf and small round cells show PAS positivity (Figure 2C). S100 (Figure 2D), LCA, smooth muscle actin, chromogranin, desmin, pancytokeratin and EMA were negative.