Table 2 Summary of the microscopic features in 50 BAP1-inactivated melanocytic tumors.
From: Novel insights into the BAP1-inactivated melanocytic tumor
Feature | Frequency |
|---|---|
Thickness | |
Range | 0.4–11 mm |
Mean | 3.1 mm |
Silhouette | |
Polypoid with collarette | 19 (38%) |
Verrucous | 3 (6%) |
Dome-shaped | 27 (54%) |
Flat | 1 (re-excision) (2%) |
Base/border | |
Flat base | 20 (40%) |
Wedge-shaped base | 20 (40%) |
Deep extension (bulb) | 9 (18%) |
Pushing border | 4 (8%) |
Epidermal changes | |
Epidermal hyperplasia (irregular) | 9 (18%) |
Epidermal atrophy/consumption (focal) | 24 (48%) |
Ulceration | 0 |
Irritation | 12 (24%) |
Junctional component | |
Basal BAP1-inactivated melanocytes | 23 (46%) |
Extensive junctional component | 12 (24%) |
Architecture and growth patterns | |
Pure | 5 (10%) |
Combined | 45 (90%) |
Associated nevus | |
Dysplastic features | 7 (14%)a |
Congenital features | 26 (52%)a |
Minimal residual nevus | 18 (36%) |
Mixed nests (with BAP1+ and BAP1− cells) | |
Junctional | 18 (36%) |
Dermal | 27 (54%) |
Arrangement of large epithelioid melanocytes | |
Nodular/sheet-like | 43 (86%) |
Nests | 26 (52%) |
Trabecules | 43 (86%) |
Discohesive (focal) | 44 (88%) |
Cytological features epithelioid melanocytes | |
Large mainly (3 × type B melanocytes) | 14 (28%) |
Small mainly (1 × type B melanocytes) | 16 (32%) |
Equal | 20 (40%) |
Pleomorphism | |
Mild | 13 (26%) |
Moderate | 36 (72%) |
Severe | 0 |
Cellular morphology of epithelioid melanocytes | |
Large Hodgkin-like | 46 (92%) |
Binucleated with mirroring nuclei (Reed-Sternberg-like) | 47 (94%) |
Clear lacunar-like cells/cytoplasmic vacuolization | 35 (70%) |
Multinucleated Popcorn/Coin-on- a-plate/ Wreath-like | 49 (98%) |
Apoptotic (Mummified cells) | 39 (78%) |
Signet ring/Rhabdoid cells | 29 (58%) |
Ghost cells | 45 (90%) |
Ball-in-mitts (Entosis) | 38 (76%) |
Micronuclei | 40 (80%) |
Spindled epithelioid cells (focally) | 3 (6%) |
Pigmented epithelioid cells | 6 (12%) |
Clear nuclear pseudoinclusions | 28 (56%) |
Eosinophilic nuclear pseudoinclusions | 26 (52%) |
Mitotic rate in epithelioid melanocytes | |
≤2 mitoses/mm2 | 45 (90%) |
>2 mitoses/mm2 | 5 (10%) |
Mitoses near base | 13 (26%) |
Adnexal, vascular, or perineural extension | |
Adnexal involvement | 13 (26%) |
Perineural arrangement | 6 (12%) |
Intravascular invasion | 0 |
Stromal changes | |
Melanin deposits | 35 (70%) |
Mucin deposits | 5 (10%) |
Adipocytic metaplasia | 6 (12%) |
Prominent vascular and/or sclerotic stroma | 5 (10%) |
Inflammatory response | |
Absent to scarce | 15 (30%) |
Moderate to heavy | 35 (70%) |
Plasma cells | 11 (22%) |
Other | |
“Squeezed” conventional melanocytes | 17 (34%) |
“Kissing” lymphocytes | 47 (94%) |
Impaired maturation (focal) | 46 (92%) |
