Table 1.
Use of cytologic examination and immunohistochemistry in narrowing the differential diagnosis of pediatric and adolescent small round blue cell tumors.
| Pediatric and adolescent “small round blue cell” tumors differential diagnosis | Distinguishing morphologic factors on aspirate/cell block | Immunohistochemical panels that may help narrow differential diagnosisb |
|---|---|---|
| Neuroblastoma | May form Homer Wright pseudorosettes with central neuropil | Synaptophysin, chromogranin |
| Osteosarcoma | May show evidence of bone formationa | IHC rarely helpful. Osteocalcin, ±cytokeratins. |
| Ewing sarcoma | May also form Homer Wright pseudorosettes | FLI1, CD99, ±synaptophysin, ±neuron-specific enolase, ±NKX2.2 |
| Rhabdomyosarcoma | Embryonal subtype: strap cells, tadpole cells | Desmin, ±myogenin, ±MyoD1 |
| High-grade carcinoma | Gland formation | Cytokeratins |
| Lymphoma | Lymphoglandular bodies | CD45, ±CD3, ± CD20 |
a
The presence of bone is more likely to be identified on the cell block preparation.
b
All the stains listed are positive in the applicable tumors, except for those listed with “±,” which designates that the stain may be positive or negative.