Purpose : Epidormoid cysts are benign epithelial cysts often ocurring within the skin of face and trunk. But carcinomatous change is rare. The authors experienced a case of squamous cell carcinoma arising from the wall of epidermoid cyst of axilla and report the radiologic and pathologic findings with a brief review of the literatures.Methods and Materials : Plain chest radiograph, US and enhanced CT of axilla were takened. We analyzed radiologic findings of squamous cell carcinoma in the wall of epidermoid cyst of axilla and correlated with pathologic findings.Results: Plain chest radiograph revealed a huge axillary mass without bony destruction or calcification. US showed a heterogenous hyperechoic mass with eccentrical cystic lesion. Outer margin of the mass was irregular. No posterior acoustic enhancement was seen. Postcontrast CT scan showed a circumscribed complex mass with irregular enhancing rim. During operation mass was located within subcutaneous layer and internal contents of the mass were brown, necrotic keratinous debries. Conclusion : Differentiation from solid tumor was difficult. But intradermal or subcutaneous location and rapid growing were characteristic.