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Dermatopathology, Diagnostics, Histology, HistoQuarterly

HistoQuarterly: PYOGENIC GRANULOMA

Working in a histology lab means that I get to see a lot of what our body looks like under the microscope.  Quarterly I will share with you some of my photos from the microscopic world of our inner space and tell you a little bit about what we’re looking at.

This quarter we’re going to take a look at a very common skin lesion called the pyogenic granuloma.

An example of a pyogenic granuloma on a finger

An example of a pyogenic granuloma on a finger [image credit: Wikimedia]

A pyogenic granuloma is a fast growing pinkish-red fleshy lesion of the skin (commonly the finger tips) or oral mucosa. They are raised lesions, sometimes presenting itself on a distinct stalk. The margin of skin around the lesion is often thickened. As they age they may darken, and they often bleed or weep if caught, so often become crusty, too.

They were initially named “botryomycosis hominis” by the two French surgeons, Poncet and Dor, who first described them in 1897. Since then they have been known by various other names including; “Pregnancy tumor”, “Eruptive hemangioma”, “Granuloma gravidarum”, “Granulation tissue-type hemangioma” and “Lobular capillary hemangioma”.

The name “pyogenic granuloma” is actually a misnomer because the lesion is not associated with pus production, and its histology does not have the appearance of a granuloma.

The lesions tend not to be painful, but due to their polypoid nature, they often get caught, which can be a nuisance, especially if they bleed or weep as a result.

So what does the histology look like?

Well, we had a really good example of one in the lab recently. Here it is on low power:

A low power H&E of a pyogenic granuloma

A low power H&E of a pyogenic granuloma

It is a great example because these types of lesions are often removed via a shave excision. This one, however, was removed with a deep excision and a considerable margin around it, so you really get to see the sharp demarcation of the start of the lesion, how it grows upwards and how it doesn’t invade any deeper than the baseline level of the epidermis. If you want a quick re-cap on what normal skin looks like, feel free to check out the skin edition of HistoQuarterly.

Back to the above image; this example of pyogenic granuloma was about 1 cm in size, it presented on a stalk (pedunculated) and was ulcerated (loss of epithelium), as most of them often are.

It may not be too obvious to see from the above low power image, but pyogenic granulomas are in fact highly vascular lesions. This is due to something called blood vessel proliferation, which in effect is vast amounts of blood vessel multiplication. At medium power, the blood vessels look like lots of little holes, some of which are filled with blood:

A medium power H&E showing blood vessels that have proliferate (multiplied) into many numbers.

A medium power H&E showing blood vessels that have proliferate (multiplied) into many numbers.

You can probably start to appreciate from the above image the previously described margin of thickened skin now shows histologically as hyperkeratosis at the base of the lesion. Also, the vascular proliferation appears to arrange itself into a lobular pattern. The tumour initiates an inflammatory response, and these inflammatory cells together with oedema, resembles the appearance of granulation tissue.

At high power, we can see that some of the blood vessels contain blood (functioning) and some of them don’t (non-functioning):

A high power H&E showing functioning and non-functioning blood vessels

A high power H&E showing functioning and non-functioning blood vessels

The layer of epidermis surrounding the lesion commonly becomes very thin and, as mentioned earlier, often ulcerates, as shown here:

A medium power H&E showing an ulcerated pyogenic granuloma

A medium power H&E showing an ulcerated pyogenic granuloma

You can see at the site labelled “ulcer”, there is no recognisable epidermis surrounding the lesion anymore. An ulcer, by definition, is an area of erosion, as shown here by the epidermis having been completely eaten into and failed to heal.

This particular ulcer has actually become infected with a type of bacteria, which can be seen as solid purple areas. A closer look:

A high power H&E showing bacteria within the ulcer

A high power H&E showing bacteria within the ulcer

It is not possible to diagnose the exact type of bacteria within the ulcer from this H&E, but with another histological tinctorial stain called the Gram stain, we would be able to identify whether or not the bacteria were of Gram positive or Gram negative nature. Ordinarily, there wouldn’t be a need to identify the bacteria because the lesion has been completely excised and the bacteria pose no threat to the individual.

Are the lesions something to worry about?

Their tendency to grow very rapidly often cause worry that they are more sinister, but they are completely benign and do not have a habit of becoming malignant. The lesions are mostly associated with previous trauma at that site, but they can also be influenced by hormones, hence why they commonly present during pregnancy.

How do we treat them?

Treatment of the lesion is often by excision but some have been known to spontaneously regress on their own.

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If you’d like to know more about oral pyogenic granulomas, these two websites are a good source of information:

Medscape

Pathology Outlines

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All images are Copyright © 2016 Della Thomas unless otherwise stated.

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About Della

Hello, my name is Della and I'm an advanced biomedical scientist in histological dissection working for the NHS in the north of England.

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Della

Della

Hello, my name is Della and I'm an advanced biomedical scientist in histological dissection working for the NHS in the north of England.

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