# Osteoid osteoma of the thumb: A case report

## TL;DR

A rare case of a benign bone tumor in the thumb was misdiagnosed as an infection but successfully treated with surgery.

## Contribution

Presentation of a rare osteoid osteoma case in the thumb with a successful surgical outcome and five-year follow-up.

## Key findings

- Osteoid osteoma in the thumb can mimic infection, leading to misdiagnosis.
- Surgical en bloc resection effectively resolved symptoms and prevented recurrence.
- CT imaging and histopathology were crucial for accurate diagnosis.

## Abstract

Osteoid osteoma (OO) is a benign bone-forming tumor that rarely affects the small bones of the hand, particularly the thumb. Its diagnosis in this location can be challenging due to its atypical presentation and the potential for mimicking other conditions.

We present the case of a 16-year-old female who presented with persistent, painful swelling of the proximal phalanx of her thumb. There was no history of trauma or infection. Radiographs revealed sclerosis and a hollowed-out lesion in the distal aspect of the phalanx, raising suspicion for chronic osteomyelitis. This initial misdiagnosis contributed to a delay in definitive treatment. Surgical en bloc resection was performed using a mid-axial approach under C-arm guidance. Intraoperative cultures were negative for microorganisms, and histopathological examination confirmed the diagnosis of OO.

OO of the thumb is extremely rare and can be misdiagnosed due to its resemblance to infectious or inflammatory conditions. Delayed diagnosis may lead to prolonged pain and functional impairment. Imaging, particularly CT scans, plays a crucial role in identifying the nidus characteristic of OO. Surgical excision remains the gold standard for treatment, providing definitive relief and preventing recurrence.

This case highlights the importance of considering OO in the differential diagnosis of persistent thumb pain and swelling, even in the absence of trauma or infection. Surgical resection provided an excellent outcome in this case, emphasizing the effectiveness of this treatment modality for OO in this unusual location.

•Rare case of osteoid osteoma in the proximal phalanx of the thumb in an adolescent.•Atypical presentation mimicked infection, leading to an initial misdiagnosis and delayed treatment.•En bloc resection was performed successfully, ensuring complete removal and symptom resolution.•Histopathological analysis confirmed diagnosis, ruling out other benign or malignant bone lesions.•Excellent long-term outcome with full recovery and no recurrence after five-year follow-up

Rare case of osteoid osteoma in the proximal phalanx of the thumb in an adolescent.

Atypical presentation mimicked infection, leading to an initial misdiagnosis and delayed treatment.

En bloc resection was performed successfully, ensuring complete removal and symptom resolution.

Histopathological analysis confirmed diagnosis, ruling out other benign or malignant bone lesions.

Excellent long-term outcome with full recovery and no recurrence after five-year follow-up