# Capillary telangiectatic osteosarcoma misdiagnosed as aneurysmal bone cyst in a 12-year-old girl: A case report

## TL;DR

A 12-year-old girl's aggressive bone tumor was initially misdiagnosed as a benign cyst, but later confirmed as telangiectatic osteosarcoma, highlighting the need for accurate diagnosis and timely treatment.

## Contribution

This case emphasizes the diagnostic challenges of telangiectatic osteosarcoma and the importance of advanced pathology and molecular testing for accurate identification.

## Key findings

- Telangiectatic osteosarcoma was misdiagnosed as an aneurysmal bone cyst, leading to delayed treatment.
- Comprehensive pathology and molecular analysis confirmed the correct diagnosis and guided effective chemotherapy.
- Limb-sparing surgery after chemotherapy successfully managed the tumor despite the initial misdiagnosis.

## Abstract

Telangiectatic osteosarcoma (TOS) is a rare and aggressive subtype of osteosarcoma that is often misdiagnosed as more benign lesions, such as aneurysmal bone cysts (ABCs) or giant cell tumors (GCTs). The accurate differentiation between these conditions is crucial to ensure timely and appropriate treatment, as misdiagnosis can lead to delayed management and poor prognoses.

We present the case of a 12-year-old girl who initially presented with left hip and proximal thigh pain, with imaging studies suggesting an ABC. Following curettage and grafting, the initial pathology report confirmed the diagnosis of ABC. However, the patient experienced rapid recurrence within two months, leading to further surgical intervention. A thorough re-evaluation of the pathological specimen revealed characteristics consistent with TOS, confirmed by immunohistochemical staining and molecular tests. The patient received four cycles of chemotherapy after the second surgery and underwent limb - salvage surgery 3 months after the operation.

This case highlights the challenges in diagnosing TOS due to its histological similarity to other giant cell-rich lesions. The initial misdiagnosis delayed the commencement of appropriate treatment. However, upon correct identification, the patient was treated with an effective chemotherapy regimen, including cisplatin, doxorubicin, and ifosfamide, resulting in significant tumor regression and control of lung metastases.

This case underscores the necessity for clinicians to maintain a high index of suspicion for TOS when evaluating aggressive bone lesions, particularly in pediatric patients. The importance of comprehensive pathological assessment, including immunohistochemistry and molecular analysis, cannot be overstated, as early and accurate diagnosis significantly influences treatment outcomes and prognosis.

•Rare TOS misdiagnosed as ABC in girl, stressing accurate giant cell assessment.•Pathology/molecular analysis confirmed TOS post-ABC, stressing advanced diagnostics.•Delayed TOS diagnosis; chemotherapy effective, improving prognosis.•Limb-sparing surgery post-chemo successful in TOS despite prior misdiagnosis.•High clinical suspicion for TOS needed in aggressive bone lesions for early treatment.

Rare TOS misdiagnosed as ABC in girl, stressing accurate giant cell assessment.

Pathology/molecular analysis confirmed TOS post-ABC, stressing advanced diagnostics.

Delayed TOS diagnosis; chemotherapy effective, improving prognosis.

Limb-sparing surgery post-chemo successful in TOS despite prior misdiagnosis.

High clinical suspicion for TOS needed in aggressive bone lesions for early treatment.