Medical Specialty >> Dermatology

Doctors Lounge - Dermatology Answers

Back to Dermatology Answers List

If you think you may have a medical emergency, call your doctor or 911 immediately. Doctors Lounge ( does not recommend or endorse any specific tests, physicians, products, procedures, opinions, or other information that may be mentioned on the Site.

DISCLAIMER: The information provided on is designed to support, not replace, the relationship that exists between a patient/site visitor and his/her physician. Please read our 'Terms and Conditions of Use' carefully before using this site.

Date of last update: 10/18/2017.

Forum Name: Dermatology Topics

Question: Why Would a Pilar Cyst Be Hollow?

 Nathalie28 - Sun Jul 04, 2010 12:42 am

I have suffered from pilar cysts on my scalp from the time I was eight years old. My father also had them. I've always had them removed without a problem. Today I went in for what I thought was a standard removal of a rather large pilar cyst – around the size of a half-dollar. Upon opening up the area, however, the doctor discovered a very minimal amount of cystic tissue. The rest of the massive lump was hollow.

I've never had this happen before and apparently the doctor hadn't either as he didn't know what to make of it. The skin on my head was hard and round just like there was a cyst underneath, but there was nothing there. Now the area seems to have gone down somewhat in size.

What caused this? Why would my head develop a "false" cyst? Could a cyst of that size have grown and then subsequently been reabsorbed by my body?
 Dr.M.Aroon kamath - Tue Jul 13, 2010 12:42 am

User avatar Hi,
Pilar cysts (trichelemmal cysts) are cysts arising from the outer root sheath of a hair follicle(the trichelemma).

These may be
- sporadic or may be
- autosomal dominantly inherited.

They can be
- solitary or
- multiple.

Once formed, they may
a) remain non-growing,
b) grow larger,
c) get inflamed or infected and go on to form an abscess,
d) occasionally extrude their contents to form a soft, cutaneous 'horn' (these horns may presumably get dislodged by activities such as combing the hair etc).
e) the cyst may burst open and remain open('marsupialized'). If the cyst cavity remails exposed, its lining eventually fuses with the surrounding epidermis to form a depression or 'crypt'. This may then lead to complete healing;
f) very rarely, malignant transformation may occur (proliferating pilar tumors).

Situations d & e described above might explain the disappearance of the cyst in your case.
Best wishes!

| Check a doctor's response to similar questions

Are you a Doctor, Pharmacist, PA or a Nurse?

Join the Doctors Lounge online medical community

  • Editorial activities: Publish, peer review, edit online articles.

  • Ask a Doctor Teams: Respond to patient questions and discuss challenging presentations with other members.

Doctors Lounge Membership Application

Tools & Services: Follow DoctorsLounge on Twitter Follow us on Twitter | RSS News | Newsletter | Contact us