OS 1  OS2 SATB2

Case history:

A 14-year-old girl presented with left hip pain. Imaging studies show a heterogeneous infiltrative lesion occupying the left hemipelvis. A biopsy was performed. (Brief History)

  1.       Conventional osteosarcoma
  2.       Conventional chondrosarcoma
  3.       Mesenchymal chondrosarcoma
  4.       Ewing sarcoma

The answer is “A”, conventional osteosarcoma

This is a conventional osteosarcoma, predominantly fibroblastic. The malignant cells are usually spindled and often, but not always demonstrate severe cytologic atypia. Tumor osteoid may be minimal and difficult to discern, especially in limited biopsy specimens.

SATB2 is a transcription factor required for osteoblast differentiation, thus is helpful in confirming the diagnosis in this setting, especially when definitive tumor osteoid is not identified. Other tissue types reportedly expressing this molecular include lower gastrointestinal epithelium, neurons and a small subset of renal cell carcinoma and mullerian primary carcinomas.

Conventional chondrosarcoma (choice B), characterized by cartilaginous matrix production, is exceeding rare in children and adolescence. Mesenchymal chondrosarcoma (C) is characterized a bimorphic pattern composed of poorly differentiated small round cells and islands of well-differentiated hyaline cartilage. Ewing sarcoma (D) is characteristically composed of small, blue, round cells.

References

  1. Conner JR, Hornick JL. SATB2is a novel marker of osteoblastic differentiation in bone and soft tissue tumours. Histopathology. 2013 Jul;63(1):36-49.
  2. Ordóñez NG. SATB2is a novel marker of osteoblastic differentiation and colorectal adenocarcinoma. Adv Anat Pathol. 2014 Jan;21(1):63-7.

Case contributed by Shi Wei, M.D., Ph.D., Professor, Anatomic Pathology, UAB Department of Pathology