Is it possible my neck lump is not a branchial cyst?

This is a continuation of the post about my cyst. I think it's sufficiently important to warrant a separate post. 

After asking many questions of the LLMs (i.e. large language models such as ChatGPT) last night and this morning, I am questioning whether we can be confident that it is in fact a branchial cyst. I now suspect it is possibly an epidermal inclusion cyst. Of course, we cannot simply trust what LLMs say, but they will usually tend to be correct and especially if they all agree with each other. This is not to say they are all agreeing with each other over these questions, but they are in the main. 

I'll quote the questions and in each case quote ChatGPT's conclusion in italics (ChatGPT based on the GPT-4 architecture). I'll place in brackets what the situation is regarding my own cyst.

1. If a cyst is composed of benign squames admixed with a mixed inflammatory infiltrate rich in neutrophils, is it more likely to be a branchial cyst, or an epidermal inclusion cyst?

Answer: If a cyst is composed of benign squames admixed with a mixed inflammatory infiltrate rich in neutrophils, it is more likely to be an epidermal inclusion cyst.

(This was the composition of my cyst back in February.)

2. Which cyst, a branchial cyst or an epidermal inclusion cyst, is more likely to develop solids within it over time? 

Answer: An epidermal inclusion cyst is more likely to develop solid contents over time compared to a branchial cleft cyst.

(8 days ago I discovered that my cyst is no longer just fluid as it was originally but has developed solids over time.)

3. If an epidermal inclusion cyst is very deep, is it conceivable the initial causal trigger could be from aggressive shaving?

Answer: Yes, an epidermal inclusion cyst can be initially caused by shaving, even if the cyst forms relatively deep within the skin.

(On the 8th of January 2024, five days before I first spotted my cyst, I decided to cut my own hair, something which I do on very odd occasions such as once a year or so. I foolishly decided to use the unguarded shaver to shave my neck and I think I was pressing down fairly hard on the relevant region. Since this has occurred before to me on the back of the neck about 3 years previously with the precise same shaver (although with the bump only lasting a few weeks) it seemed to me that it was highly likely that this was the initial causal trigger. However, the ENT specialist and other clinicians and technicians were adamant in dismissing this possibility. More on this after the next related question.)

4. If a branchial cyst is deep, is it conceivable the initial causal trigger could be from aggressive shaving?

Answer: Branchial Cysts: Cannot be caused by aggressive shaving as they are congenital in nature. Shaving or skin trauma may exacerbate symptoms or cause secondary infection, but it is not the initial cause.

(I wonder if, perhaps, this is why the ENT specialist and others are so dismissive of the suggestion that the initial causal trigger was shaving? In other words, they are convinced it is a branchial cyst, and this being so, then the shaving cannot have been a causal trigger. Of course, if true, the prior assumption of a branchial cyst needs to be challenged. There might, however, be other reasons why shaving being a causal trigger are confidently dismissed, I simply don't know. However, it sits uneasily with me the suggestion it is wholly happenstance that I happened to be using that shaver just five days previous to the cyst first appearing. And that shaver has form! Contrariwise, it seems it has to be assumed that a branchial cyst just suddenly, ostensibly randomly appeared with no discernable cause.)

5. Which cyst, a branchial or Epidermal inclusion cyst, is more likely to respond favourably to warm compresses?

Answer: Epidermal inclusion cysts are more likely to respond favorably to warm compresses compared to branchial cleft cysts.

(From the 23rd May to the 10th of June, the cyst was growing hugely, but since that date I've been using warm compresses once every 4 hours or so, and it seems to have virtually stopped growing.)

6. Can an Epidermal Inclusion Cyst appear in the same place as a branchial cyst, hence making it difficult to distinguish the two?

Answer: Yes, an epidermal inclusion cyst can appear in the same anatomical area as a branchial cleft cyst, which can indeed make it challenging to distinguish between the two.

7. Would an epidermal inclusion cyst located in the same area as a branchial cyst, also be equally likely to cause swallowing difficulties? Or would it tend to grow outwards from the neck more rather than inwards?

Answer: An epidermal inclusion cyst located in the same area as a branchial cleft cyst is less likely to cause swallowing difficulties compared to a branchial cleft cyst. This is primarily due to differences in their anatomical location, growth patterns, and typical symptoms.

(Mine causes no swallowing difficulties or other difficulties like this, and seems to grow outwards.)

8. Is it difficult to clinically distinguish between a branchial cyst and an epidermal inclusion cyst?

Answer: Yes, clinically distinguishing between a branchial cleft cyst and an epidermal inclusion cyst can be challenging due to some overlapping features. However, there are specific characteristics, diagnostic methods, and clinical considerations that can help differentiate between these two types of cysts. 

(So it's challenging, although not impossible to distinguish. In conjunction with all the other considerations, I think there is a possibility they might be mistaken in concluding it's a branchial cyst.)

9. Which is more likely to undergo a rapid growth spurt, a branchial cyst or an epidermal inclusion cyst?

Answer: Epidermal inclusion cysts are generally more likely to experience rapid growth due to inflammation or infection, whereas branchial cleft cysts usually grow slowly unless secondary complications arise.

(The fact my cyst experienced rapid growth from the 23rd May to the 10th June lends slight support to it being an epidermal inclusion cyst.)

10. For someone who is ** years of age, is the development of an epidermal inclusion cysts more likely than the development of a branchial cyst? And if so, how much more likely? (I'm hiding my age in case of identity theft, but I'm quite old.)

Answer:  For a **-year-old individual: The development of an epidermal inclusion cyst is significantly more likely than the development of a branchial cleft cyst (bold as in original).

(It hazards a ratio of 5-10 times more common.)

OK, I hold my hands up and admit I have virtually no medical knowledge whatsoever. But I do wonder if they are merely going by the tests and not taking a blind bit of notice of my own observations? It certainly appears that way. They appear to listen but do not take any notes. Indeed, the ENT specialist I spoke to yesterday had a slightly sceptical look on her face when I mentioned the effectiveness of warm compresses. So my impression is that my personal experiences are simply not taken into account at all, which I find astonishing. Surely all pertinent evidence has to be assessed if we want to maximise the chance of a correct diagnosis? 

On the other hand, I do not know what makes them confident that it is a branchial cyst. There might very well be information I am unaware of that makes their diagnosis highly likely, if not certain. 

Also, I'm not sure it makes much difference anyway. Both require surgical removal. A malignant epidermal inclusion cyst is vanishingly rare, though (about 0.01% of lumps?), whereas a malignant branchial cyst is merely rare (about 1%). Hence, if it is an epidermal inclusion cyst, it might be deemed that a PET scan would be inappropriate.