Telangiectatic osteosarcoma (TOS) is a rare variant of osteosarcoma that typically affects young individuals and long bones. The case under discussion was seen in the mandible of a 57-year-old female and had rapidly grown in size within a week. Microscopically, the tumour was characterised by large vascular cavities surrounded by anaplastic cells. Thin lacy tumour osteoid was observed at various foci. Abundant multinucleated osteoclastic giant cells along with areas of necrosis were also noted. The tumour cells were positive for SATB2, while negative for Cytokeratin AE1/3, CD 34. Ki-67 positivity was observed in more than 50% of tumour cells. A diagnosis of high grade telangiectatic osteosarcoma was thus made.

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Primary thyroid osteosarcoma is an extremely rare tumor which is associated with a poor prognosis. In this study, we describe an additional case. A 4.5 × 3.8 cm irregular heterogeneous nodule was examined in the left thyroid gland of a 72-year-old woman. Cytological smears and histopathological specimens showed typical features of osteosarcoma with a neoplastic lesion rich in spindle cells with occasional multinucleated cells and lace-like osteoid matrix. Negative immunoreaction with epithelial markers and positive immunoreaction with SATB2 and low Ki-67 labeling index suggested the diagnosis of osteosarcoma. Multiple KMT2C gene mutations determined by next-generation sequencing further confirmed the diagnosis.

SATB2-associated syndrome (SAS) is an autosomal dominant neurogenetic multisystemic disorder. We describe two individuals with global developmental delay and hypotonia who underwent an extensive evaluation to rule out an underlying mitochondrial disorder before their eventual diagnosis of SAS. Although the strict application of the clinical mitochondrial disease score only led to the designation of \"possible\" mitochondrial disorder for these two individuals, other documented abnormalities included nonspecific neuroimaging findings on magnetic resonance imaging and magnetic resonance spectroscopy, decreased complex I activity on muscle biopsy for patient 2, and variation in the size and relative proportion of types of muscle fibers in the muscle biopsies that were aligned with mitochondrial diseases. SAS should be in the differential diagnoses of mitochondrial disorders, and broad-spectrum diagnostic tests such as exome sequencing need to be considered early in the evaluation process of undiagnosed neurodevelopmental disorders.