Tumors of unknown histogenesis |
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ES/PNET |
Rare basal lamina |
Primitive polygonal cells containing sparse organelles, abundant glycogen, occasional neural differentiation; rare epithelial differentiation such as tonofilaments |
Neuroblastoma |
Rare basal lamina |
Round cells having cell processes containing neural differentiation such as microtubules, neurofilaments, neurosecretory granules, glycogen, synaptic vesicles |
Desmoplastic small round cell tumor |
Discontinuous basal lamina |
Paranuclear whorls of intermediate filaments, rare dense core granules, scant organelles, occasional microtubules, glycogen particles |
Malignant rhabdoid tumor |
No basal lamina |
Paranuclear bundles of cytoplasmic intermediate filaments (about 10 nm in thickness), glycogen particles |
Soft tissue tumor |
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Monophasic synovial sarcoma |
Focal basal lamina |
Spindle to oval cells mimicking fibroblasts (less RERs than fibroblasts) having intermediate filaments, microvilli, pinocytotic vesicles |
Small cell schwannoma or small cell malignant peripheral nerve sheath tumor |
Continuous reduplicated basal lamina |
Long-spacing collagen, i.e., Luse bodies |
Alveolar rhabdomyosarcoma, solid variant |
Basal lamina |
Myosin-ribosome complexes, dense plaques |
Small cell osteosarcoma |
No basal lamina |
Fibroblast-like cells containing abundant RERs, glycogen, flocculent premineralized stage osteoid matrix, needle-like dense hydroxyapatite crystals on collagen fibrils, i.e., osteoid |
Mesenchymal chondrosarcoma |
No basal lamina |
Glycogen in cytoplasm, rare scalloped villous cell surfaces |
Hematologic malignancies |
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Leukemia/myeloid sarcoma |
No basal lamina |
Ovoid-shaped myeloid cells containing myeloid granules of various stage or Auer bodies |
Malignant lymphoma |
No basal lamina |
Polygonal shaped cells with abundant ribosomes or variable amount of RERs |
Others |
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Small cell or rhabdoid melanoma |
Focal basal lamina |
Round cells having Golgi complex, atypical melanosomes of various stage |