74, XY, nasal bridge. Impression was ?BCC . C22-1116
And that's exactly what it is, meaning BCC. A good general rule of thumb to use when encountering extreme oddball subtypes of BCC (or when your spidey sense tells you that might be the situation in which you find yourself) is to see if you can find a focus of mainstream BCC as an 'in' to your diagnosis. Often you can, if you look hard enough. Not always, but very often. That helps, because otherwise the diagnostic findings can appear or feel very tricky and deceptive. The rule of thumb applies to all kinds of subtypes, whether it be clear cell, granular cell, myoepithelial with inclusions (and actin positivity), or whatever.
As you thumb through the pics that accompany this post, it's clear that there is a clear cell tumor right away. In the top piece of the bisected shave, the rule of thumb mentioned in the above paragraph holds true, as you can see a tiny focus of reasonably conventional BCC that has separated itself from adjacent tissue or stroma.
In the bottom piece of tissue, it's a different story, because there isn't much that looks like BCC there. From what's there, you might think clear cell SCC or trichilemmoma or conceivably even clear cell sebaceous. It turns out that the tumor in both pieces expresses Ber-EP4 at Level 11, so that helps a lot (Ber-EP4 stain now included as the final immunopic). Remember that trichilemmoma is utterly Ber-phobic , so that's completely out. And it is very uncommon to see mega-Ber expression by any sebaceous tumor.
There are at least 2 other small points to be made here:
1. PRAME expression by BCC is common (the nuclear stain that is included represents a PRAME preparation). For virtually all cases, the overlap between BCC and melanoma is pretty small, but I can imagine a diabolical scenario in which a biopsy with some irritation effect shows a little pagetoid scatter, and somebody gets off on the wrong foot and sees some PRAME expression and goes it the wrong direction. It could happen, keep it in mind.
2. My jokey term for extreme clear cell change is 'superclear', and this particular tumor is BCC of the superclear type. It turns out superclear BCC is not rare. In a similar vein, most trichilemmomas have clear cells, but occasional trichilemmomas can be superclear, and in that context it gets harder to match the name to the face, because some of your usual diagnostic clues are distorted. I've also seen superclear change in syringoma, hidradenoma, poroma, and various other adnexal tumors.
A strong shoutout goes to Tom Nicotri, he's my co-conspirator here. A link to another type of clear cell adnexal tumor is here: https://kikoxp.com/posts/13482. The one at the link isn't superclear, but we'll get one posted sooner or later.
And that's exactly what it is, meaning BCC. A good general rule of thumb to use when encountering extreme oddball subtypes of BCC (or when your spidey sense tells you that might be the situation in which you find yourself) is to see if you can find a focus of mainstream BCC as an 'in' to your diagnosis. Often you can, if you look hard enough. Not always, but very often. That helps, because otherwise the diagnostic findings can appear or feel very tricky and deceptive. The rule of thumb applies to all kinds of subtypes, whether it be clear cell, granular cell, myoepithelial with inclusions (and actin positivity), or whatever.
As you thumb through the pics that accompany this post, it's clear that there is a clear cell tumor right away. In the top piece of the bisected shave, the rule of thumb mentioned in the above paragraph holds true, as you can see a tiny focus of reasonably conventional BCC that has separated itself from adjacent tissue or stroma.
In the bottom piece of tissue, it's a different story, because there isn't much that looks like BCC there. From what's there, you might think clear cell SCC or trichilemmoma or conceivably even clear cell sebaceous. It turns out that the tumor in both pieces expresses Ber-EP4 at Level 11, so that helps a lot (Ber-EP4 stain now included as the final immunopic). Remember that trichilemmoma is utterly Ber-phobic , so that's completely out. And it is very uncommon to see mega-Ber expression by any sebaceous tumor.
There are at least 2 other small points to be made here:
1. PRAME expression by BCC is common (the nuclear stain that is included represents a PRAME preparation). For virtually all cases, the overlap between BCC and melanoma is pretty small, but I can imagine a diabolical scenario in which a biopsy with some irritation effect shows a little pagetoid scatter, and somebody gets off on the wrong foot and sees some PRAME expression and goes it the wrong direction. It could happen, keep it in mind.
2. My jokey term for extreme clear cell change is 'superclear', and this particular tumor is BCC of the superclear type. It turns out superclear BCC is not rare. In a similar vein, most trichilemmomas have clear cells, but occasional trichilemmomas can be superclear, and in that context it gets harder to match the name to the face, because some of your usual diagnostic clues are distorted. I've also seen superclear change in syringoma, hidradenoma, poroma, and various other adnexal tumors.
A strong shoutout goes to Tom Nicotri, he's my co-conspirator here. A link to another type of clear cell adnexal tumor is here: https://kikoxp.com/posts/13482. The one at the link isn't superclear, but we'll get one posted sooner or later.
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