Soft tissue tumors are mostly palpable lesions. A small nodule is the most frequent clinical presentation. The high spatial resolution of ultrasound (US)allows an adecuate representation of this lesions.
The purpose is to correlate the findings of ultrasound with the histological results.

A case serie of 173 dermatological soft tissues masses with US are analized, 90 % less than 25 mm. All US exams were performed with 10 - 12 MHz transducer and pad gel.
Solid or cystic nature, anatomic layer involved and the correlation between US and histological diagnosis were analized.

The tumor location was diagnosed by US,corresponding : 15 were dermal masses, 89 hypodermal, 26 dermal-hypodermal, 26 fascio-aponeurotic, 15 muscular and
2 cases have more than two layers involved.
In 82 % of the cases(141/173) the US diagnosis was correct, in 9 % indeterminate and in 9 % incorrect.
In those cases were US was able to recognize typical patterns the final diagnosis was pilomatrixoma, lipoma, hemangioma, infundibular cyst, triquilemmal cyst.
Solid or cystic nature were detected corectly by US in 167/173 lesions(96.5 %), and incorrect in 6/173 (3.5 %).

Skin ultrasonography maybe a valuable tool in the assessment of dermatological lesions under 25 mm.
A well despiction of the different skin layers allows
to recognize the depth and location of a soft tissue mass.
Knowledge of typical US patterns may triage lesions improving the diferential diagnosis.