J Pathol Transl Med.  2015 Mar;49(2):93-101. 10.4132/jptm.2015.01.30.

Utility of Transmission Electron Microscopy in Small Round Cell Tumors

• Kim NR
• Ha SY
• Cho HY

• KMID: 2381362
• DOI: http://doi.org/10.4132/jptm.2015.01.30

Abstract

Small round cell tumors (SRCTs) are a heterogeneous group of neoplasms composed of small, primitive, and undifferentiated cells sharing similar histology under light microscopy. SRCTs include Ewing sarcoma/peripheral neuroectodermal tumor family tumors, neuroblastoma, desmoplastic SRCT, rhabdomyosarcoma, poorly differentiated round cell synovial sarcoma, mesenchymal chondrosarcoma, small cell osteosarcoma, small cell malignant peripheral nerve sheath tumor, and small cell schwannoma. Non-Hodgkin\'s malignant lymphoma, myeloid sarcoma, malignant melanoma, and gastrointestinal stromal tumor may also present as SRCT. The current shift towards immunohistochemistry and cytogenetic molecular techniques for SRCT may be inappropriate because of antigenic overlapping or inconclusive molecular results due to the lack of differentiation of primitive cells and unavailable genetic service or limited moleculocytogenetic experience. Although usage has declined, electron microscopy (EM) remains very useful and shows salient features for the diagnosis of SRCTs. Although EM is not always required, it provides reliability and validity in the diagnosis of SRCT. Here, the ultrastructural characteristics of SRCTs are reviewed and we suggest that EM would be utilized as one of the reliable modalities for the diagnosis of undifferentiated and poorly differentiated SRCTs.

Keyword

Small round cell tumor; Microscopy, electron; Pathology

MeSH Terms

Chondrosarcoma, Mesenchymal
Cytogenetics
Diagnosis
Gastrointestinal Stromal Tumors
Genetic Services
Humans
Immunohistochemistry
Lymphoma
Melanoma
Microscopy
Microscopy, Electron
Microscopy, Electron, Transmission*
Neurilemmoma
Neuroblastoma
Neuroectodermal Tumors
Osteosarcoma
Pathology
Peripheral Nerves
Reproducibility of Results
Rhabdomyosarcoma
Sarcoma, Myeloid
Sarcoma, Synovial

Figure

• 

  Fig. 1. (A) Ewing sarcoma shows polygonal shaped cells having large round cells and a small amount of cytoplasm with mainly glycogen pools (arrow) (×7,500). Inset indicates abundant cytoplasmic glycogen particles (×10,000). (B) Tumor cells of malignant rhabdoid tumor show paranuclear whorls packed with intermediate filaments intermingled with cytoplasmic organelles (×2,000). Inset shows paranuclear whorls filled with dense intermediate filaments, dilated rough endoplasmic reticulum (RER) cisternae and degenerated mitochondria (×8,000). (C) Neuroblastoma. Round shaped tumor cells have neurosecretory dense core granules in the cytoplasm (×8,000). (D) Small cell osteosarcoma shows ovoid shaped tumor cells containing a moderate amount of mitochondria and ribosomes with dilated RERs (×v8,500). (E) Alveolar rhabdomyosarcoma, solid variant. Closely apposed round to ovoid shaped cells have irregular shaped nuclei and a moderate amount of cytoplasm containing lipid vacuoles, mitochondria, and Golgi apparatuses (×3,500). Arrow indicates myosin-ribosome complexes (×12,000). (F) Myeloid sarcoma demonstrates cytoplasmic myeloid granules, measuring 200 nm on average (×1,500). Inset shows membrane bound myeloid granules (×6,000).

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