Small cell osteosarcoma morphological overlap with Ewings sarcoma: A case report

• Author Details:   
• Sangeetha Sundaram ^*
• Reshma Pagidyala
• Ashwini HN

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Background: Small cell osteosarcoma is an uncommon, aggressive subtype of conventional osteosarcoma characterized by small round cell morphology. Due to its histological overlap with Ewing sarcoma, accurate diagnosis remains challenging but is crucial for determining appropriate treatment and prognosis.
Case Presentation: A 22-year-old male presented with left knee pain and swelling following trauma. Imaging revealed irregular trabecular and cortical features in the distal femur. Biopsy showed sheets of small, round tumor cells with hyperchromatic nuclei, high mitotic activity, and osteoid deposition in a lacy pattern. Given the morphological resemblance to Ewing sarcoma, immunohistochemistry was performed. The tumor cells showed strong nuclear positivity for SATB2, confirming the diagnosis of small cell osteosarcoma.
Conclusion: This case highlights the diagnostic challenges posed by small cell osteosarcoma due to its histologic similarity to Ewing sarcoma. It emphasizes the pivotal role of SATB2 immunostaining in distinguishing between these entities and underscores the need for an integrated diagnostic approach that combines clinical, radiological, histological, and immunohistochemical data

Keywords: Small cell osteosarcoma, Ewing sarcoma, SATB2.