Category: General Pathology

What is a hamartoma?

Whenever I talk about “tumours”  I always mention hamartomas as one of the possible causes.

I describe them as a mass made up of the tissues usually present at a particular site but with an abnormal architectural arrangement forming a mass.  I usually give the example of a pulmonary hamartoma which appears on a chest X-ray as a tumour and lead to concern that it might be neoplastic. When biopsied they are seen to be composed of a disorganised mixed of mature cartilage, muscle and respiratory epithelium.

Curiously when I looked up hamartomas in the excellent 15th Edition of Muir’s Textbook of Pathology the only mention in the index was a reference breast hamartomas  –  a small, but surprising lapse.  On the other hand,  Robins Basic Pathology (10th Edition)  has more. It says that while hamartomas have, up till now,  been considered to be developmental in origin they have been shown to have clonal chromosomal aberrations and therefore should be considered neoplastic. This was news to me. No reference was given so I will have to look this up and will come back to this in a future post.  I do know that hamartomas carry a small risk of malignant change. An example of this is the multiple hamartomatous polyps seen in the Peutz-Jegher’s Syndrome.

Now for some pictures. This is a lung hamartoma and macroscopically looks extremely worrying!


Microscopically, this hamartoma is seen to, reassuringly, be composed of mature cartilage and respiratory epithelium which is lining the clefts.