Published in:
01-10-2015 | Classics in Abdominal Imaging
The “dot–dash” sign
Published in: Abdominal Radiology | Issue 7/2015
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“Dots and dashes” (Fig. 1) metaphorically describe the classic sonographic appearance of echogenic hair within mature cystic teratomas (Fig. 2). Mature cystic teratomas, also known as dermoid cysts, are composed of at least two of the three germ cell layers (endoderm, mesoderm, and ectoderm) and represent the most common germ cell neoplasm [1]. Most mature cystic teratomas can be diagnosed by ultrasound (with a reported sensitivity of 58% and specificity of 99%) [2]. In indeterminate cases, these lesions sometimes require further characterization by CT (Fig. 3) or MR to confirm an internal fat component [3].
Fig. 1
The telegraph was developed to transmit information as a sequence of dots and dashes across wires to communicate over long distances. A dot and a dash represent the letter “A” in the International Morse code. Adopted from http://www.morsex.com/skcc/ retrieved 2/5/2015.
Fig. 2
Transverse sonographic image of a heterogeneous right ovarian cystic mass demonstrating the “dot–dash sign” reflecting hair with different orientations within a mature cystic teratoma.
Fig. 3
CT correlate demonstrating hair and fat within the right adnexal lesion confirming the diagnosis of a mature cystic teratoma. Note the presence of bilateral mature cystic teratomas which is reported in approximately 10% of cases.
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