What is a vocal cord (fold) cyst?
A vocal cord cyst is a three dimensional, spherical or ovoid, non-cancerous structure buried below the surface of one, or rarely both, vocal cords (folds). It typically causes hoarseness by either impairing how the vocal cords close and/or how they vibrate during speaking and/or singing. A cyst can be fluid filled (mucus retention cyst) or more rarely, solid (keratin, or epidermoid cyst). While epidermoid cysts tend to be more opaque white in color, it is usually very difficult to predict which type of cyst is present without an operation.
While a vocal cord cyst is usually acquired (many times in the setting of excessive voice use or sometimes after excessive coughing), it may also be congenital (eg present from birth).

Treatment
Occasionally, a mucus retention cyst can spontaneously rupture on its own, with resulting temporary vocal improvement, but it typically re-accumulates with time and hoarseness will therefore usually return. On the other hand, an epidermoid cyst tends to remain constant or expand over time. In general, treatment for both types of vocal cord cysts, requires surgical removal via microlaryngoscopy [hyperlink to microlaryngoscopy page] in order to most reliably restore the voice.
Vocal cord (fold) cyst removal surgery involves meticulous dissection and attention to detail on the part of a laryngeal surgeon. Failure to do so can result in rupture of the thin cyst wall (in the case of the more common mucus retention cyst) early on in the operation, making identification of the decompressed cyst wall very difficult. If a cyst wall remnant is left behind, the cyst can re-accumulate, requiring revision surgery. A surgery that simply drains a mucus retention cyst may be only temporary in its effect and is likely best avoided.
While the borders of a vocal cord cyst represent a very discrete surgical target, this type of phonosurgery [link to phonosurgery page] can be challenging due to the need for such high precision. In addition to attempting not to rupture the cyst during removal, the surgeon must maximally preserve the vibratory tissue of the vocal cord that surrounds the cyst in order to optimize the vocal outcome. This type of vocal cord surgery is best performed by a highly-skilled and experienced laryngeal surgeon.
Before Vocal Cord Cyst Removal Surgery
After Vocal Cord Cyst Removal Surgery

Left vocal cord cyst (right side of image), as viewed in the office.

Same cyst as in the office, now viewed in the operating room under a microscope.

Microscissors have been used to create an incision in the epithelium that is laying over the cyst. It is crucial not to rupture the cyst at the onset of the dissection when doing this.

After careful dissection, the discrete cyst is now partially visible as a three dimensional lesion, buried within the vibratory layer of the vocal cord. This vibratory layer should be maximally preserved during surgery to optimize the vocal outcome.
Before Vocal Cord Cyst Removal Surgery
After Vocal Cord Cyst Removal Surgery
See and Hear Examples of Vocal Cord Cysts - Before and After Surgery

Before
Right vocal cord cyst (left side of image), before surgery.

After
After vocal cord cyst removal surgery (3 months).

Before
Right vocal cord cyst (left side of image), before surgery.

After
After vocal cord cyst removal surgery (3 months).