{'fraction_non_alphanumeric': 0.03010625737898465, 'fraction_numerical': 0.010625737898465172, 'mean_word_length': 4.76530612244898, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Alveolar soft-part sarcoma of the head and neck: clinical and imaging features in five cases.

BACKGROUND AND PURPOSE
Alveolar soft-part sarcoma (ASPS) of the head and neck is an extremely rare malignancy. Although the clinical and imaging features of this tumor have been reported, a periodic review of unusual tumors is useful. The purpose of this study was to describe the clinical and imaging features of ASPS of the head and neck.


METHODS
Between January 1990 and May 2004 at our institution, five head and neck ASPS were diagnosed in five patients (two male and three female patients; age range, 4-22 years). Clinical and imaging findings were reviewed retrospectively. Imaging studies consisted of contrast material-enhanced CT (in four patients), MR imaging (in four patients), and digital subtraction angiography (in two patients).


RESULTS
The locations of the tumor were tongue in two cases, larynx in one case, buccal space in one case, and paravertebral space in one case. This tumor appeared as a large lobulating-contoured mass with high signal intensity and flow voids on T2-weighted images and showed strong enhancement on contrast-enhanced CT and MR images. Preoperative angiography showed high vascularity. Wide surgical excisions were performed in four cases. Mean follow-up periods were 16 months (range, 6-30 months), and no recurrence was noted except for the laryngeal case.


CONCLUSION
ASPS should be included in the differential diagnosis of head and neck tumor when a slow-growing, large mass with high signal intensity and flow voids on T2-weighted images and strong enhancement on contrast-enhanced CT or MR image is seen, particularly in young female patients.