Mesenchymal Chondrosarcoma of the Maxillary Alveolar Bone in a 6-Year-Old Girl

Malignant small round blue cell tumors encompass a diverse group of aggressive neoplasms that share overlapping histological features, making diagnosis challenging based on morphology alone. We share a case of mesenchymal chondrosarcoma to illustrate this challenge and discuss the differential diagnosis. Soft, cream-tan tissue fragments with tan, grainy surfaces were submitted from an incisional biopsy taken from the left maxillary alveolar bone of a 6 year-old female. Microscopically, the tumor was composed primarily of sheets of morphologically undifferentiated monomorphic small blue round cells with hyperchromatic nuclei, scant cytoplasm, and poorly defined cell borders interrupted by staghorn shaped vascular structures. Admixed within the sheets of tumor cells were abrupt transitions to islands of mature, well-differentiated hyaline cartilage. (Figure 1).