Pilar Cyst of the breast
A pilar cyst is a build up of fluid and keratin just under the skin, that can develop around the root-sheath of hair follicles. A pilar cyst is a sub-type of epidermoid cyst, and they are often described using the same general terms. Specialists also sometimes refer to a pilar cyst as a:- a
- Isthmus-catagen cyst
- trichilemmal cyst
I just want to let you know that this page is getting a little bit old now, but it is still very useful. However, I have a newer version with more up-to-date information on Breast Cysts including Pilar Breast Cysts.
Pilar cysts tend to form in areas of high hair concentrations so about 90% of them form on the scalp. The other 10% tend to form in various areas of the body and rarely on the breast. Essentially a pilar or trichilemmal cyst, forms when there are large amounts of keratin in the ‘root sheath’ area of a hair follicle within a short time span.
Breast pilar cysts are benign
Pilar cysts are smooth and movable. Often a woman will find a breast lump on self examination and bring it to the attention of her family physician. Generally speaking, pilar cysts have no symptoms. But, they can become infected in which case they can become red, swollen and painful. Pilar cysts are non-cancerous (benign).
There are exceedingly rare reports of pilar cysts which become cancerous, but if a woman brings a lump to the attention of breast cancer screening physicians and finds out it is a pilar cyst, this is good news. It is not breast cancer.
Pilar cysts on the breast often occur in multiples
The development of a pilar cyst is far more common in women than in men and they tend to occur in older women the most. About 70% of the time they occur in multiples, and are ‘solitary’ about 30% of the time. Up to 10% of the population will likely develop one or more pilar cysts at some point in their lives.
No one knows exactly what causes a pilar cyst, but it may be that they form due to the ‘budding’ from the external root sheath (the trichilemmal). Pilar cysts are believed to be ‘genetically pre-determined’ as they tend to run in families.
Pilar Tumors (on the breast)
Very rarely, pilar cysts may show rapid (proliferative) cell growth and become more solid. At this point medics would call the lesions ‘pilar tumors’. They are non-cancerous, but they can grow aggressively and become so large that surgical removal is necessary.
Usually, the clinical presentation of a proliferative pilar tumor (PPT) is of a long-standing pilar or other epidermoid cyst that slowly progresses to a mass often with a history of inflammation.
Pilar tumors (also called trichilemmomas) are clinically benign but they can show:-
- mitotic cells
- nuclear atypia
- dyskeratotic cells: cells which have changed into a ‘white-plaque‘ form and this can be a misleading indicator of possible skin carcinoma.
Pilar breast tumors grow quickly and can metastasize
On mammogram, a pilar tumor may appear as a lobulated, well-circumscribed mass, and externally the skin may be ulcerated and atrophied. Pilar tumors, occuring on the breast or anywhere else, have to be followed a little more closely.
While they are mostly benign, they have been known to grow in a highly proliferative way locally, and even to metastasize (the ability to metastasize more or less defines ‘malignancy‘) So, the concern would be that while a proliferative pilar tumor is not really causing any problems, it might start to develop on a critical organ or the brain, where it could cause serious problems.
Trichilemmomas usually range in size from 1 cm to 10 cm in diameter, but, they can really grow sometimes, even reaching sizes up to 25 cm in diameter.
Treatment of pilar cysts on the breast
Since pilar cysts are benign, not cancerous, and almost always have no association with breast carcinoma at all, it is really not necessary to treat them. But, they can grow and at a certain point cause a cosmetic concern so sometimes medics will drain them or surgically remove them.
Of course, if the cyst has become infected, those symptoms will most likely be treated with oral antibiotics.
For further reading, I suggest you visit this page which has some information on epidermoid cysts of the breast, as well as this page for sebaceous breast carcinoma.
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