Table 2 Comparison between DSRCT and other small round cell tumors

Morphological characteristics

Nests of small round cells vary in size and shape, and there are a large number of fibrous connective tissue stroma between the nests of tumor cells. Tumor cells are closely arranged, thin and sparse, with unclear cell boundaries, round or oval nuclei, hyperchromatic nuclei, unclear nucleoli, and mitotic figures are easy to see

Round cells are compactly patchy/lobular, and fibrovascular septa are observed between lobules with varying width of fibrous connective tissue. The cytoplasm of the tumor cells is scarce and unclear, but some of the cytoplasmic margins could be bright or vacuolar. The nuclei are round/oval, dark-stained/uniform pepper-salt-like, and the mitotic figures vary.

Round cells are nested/lobulated, and interlobular spaces are vascular-rich fibrous connective tissue. Tumor cells differentiate in different degrees. The well-differentiated nuclei of tumor cells have no obvious atypia, fine chromatin, no obvious nucleoli, few mitotic images and more nerve fiber networks in the interstitium. The poorly differentiated tumors have obvious nuclear atypia, easily seen mitotic images, few/absent interstitial fibrous networks and a large number of necrosis.

Small round cells without specific morphology

Immunohistochemistry

Multidirectional differentiation and positive expression: epithelial marker, neuroendocrine marker, WT-1, Desmin (paranuclear point positive), Vimentin (paranuclear point positive); negative: CD99

Positive expression: CD99, Vimentin, CyclinD1;

Different degrees of expression: neuroendocrine markers;

No expression: epithelial markers, WT-1, Desmin, S-100, NF

Positive expression: neuroendocrine markers (such as NSE, Syn), NF, GFAP, S-100 (sertoli cells around the cancer nest +), epithelial markers (a few weak expression of low molecular keratin);

No expression: Desmin, EMA, CD99

Positive expression: epithelial markers; Partial expression of neuroendocrine markers; lack of multidirectional differentiation; Negative expression: Desmin et al.

Molecular pathology

EWS-WT1 gene fusion

EWS-FLI-1 gene fusion

No specific molecular changes

No specific molecular changes

Clinical features

> 95% occurred in pelvic and abdominal cavity, <  5% in paranasal sinuses, pleura, testis, intracranial, liver, lung, mediastinum, ovary, pancreas, etc

Usually occurs in lower limbs, spine, retroperitoneum, pleura, etc. and can also occur in nasal cavity and paranasal sinuses

Prevalent in upper turbinate, ethmoidal plate, upper third of nasal cavity (usually in olfactory cleft)

Can occur in all parts of the body