bone-forming Ewing sarcoma

Digital case (Digital slides)

 HPC:376 : EWSR1-FLI1+ bone-forming Ewing sarcoma (EWSR1-FLI1+ small cell osteosarcoma)

Definition: Small cell osteosarcoma is a distinct subtype with a histologic appearance in which the bulk of the lesion is composed of round malignant cells with minimal areas of spindle cells. Osteoid production is always present.

Small cell osteosarcoma (or "bone-forming Ewing sarcoma") may present a challenging primary diagnosis on cytologic assessment owing to its rarity and its morphologic similarity to other small round blue cell tumors.

Small cell osteosarcoma shares many of the well-described cytomorphologic features of classic osteosarcoma, but the relatively small cells, round hyperchromatic nuclei, and scant osteoid constitute the common denominator. Correlation with radiographic findings and ancillary tests can aid in definitive diagnosis.

Synopsis

 relatively small to intermediate cell size
 high nuclear/cytoplasmic ratios
 round nuclei
 minimal anisonucleosis
 finely granular nuclear chromatin
 fine cytoplasmic vacuoles
 only rare osteoid.

Open access references

 Small cell osteosarcoma: cytopathologic characteristics and differential diagnosis. Bishop JA, Shum CH, Sheth S, Wakely PE Jr, Ali SZ. Am J Clin Pathol 2010;133(5):756-61. PMID: #20395522# (Free)

References

 Histopathological characterization of small cell osteosarcoma with immunohistochemistry and molecular genetic support. A study of 10 cases. Machado I, Alberghini M, Giner F, Corrigan M, O’Sullivan M, Noguera R, Pellin A, Bertoni F, Llombart-Bosch A. Histopathology 2010;57(1):162-7. PMID: #20557371#

 Bertoni F, Present D, Bacchini P, Pignatti G, Picci P, Campanacci M. The Istituto Rizzoli experience with small cell osteosarcoma. Cancer 1989;64(12):2591-9. PMID: #2684389#

 Ayala AG, Ro JY, Raymond AK, Jaffe N, Chawla S, Carrasco H, Link M, Jimenez J, Edeiken J, Wallace S, et al. Small cell osteosarcoma. A clinicopathologic study of 27 cases. Cancer 1989;64(10):2162-73