Acral Spitz Nevi
Bibliographic record
Abstract
Spitz nevi on acral sites are rare and poorly documented. The combination of Spitzoid cytomorphology and atypical architectural features of the junctional component may lead to an erroneous diagnosis of melanoma. To study the clinicopthologic and immunohistochemical features, 50 Spitz nevi localized on the distal extremities were retrieved from departmental files. Clinical data and follow-up were obtained and the histologic features were analyzed. P16 and P21 immunohistochemical staining of the dermal component was compared with that of 10 acral lentiginous melanomas and 10 acral nevi. Acral Spitz nevi affected young adults (median: 24.5 y; range: 4 to 61 y) with a female predominence and a predilection for the feet. They were pigmented measuring 1 to 15 mm (median: 4 mm). Follow-up, available for 45 patients (median: 48 mo; range: 4 to 228 mo), revealed no local recurrence, metastasis or mortality. Histologically, acral Spitz nevi were composed of large epithelioid and/or spindled melanocytes. They were well circumscribed with occasional asymmetry. The junctional component was broad with a lentiginous and nested growth and shoulder formation. Marked pagetoid spread and transepidermal elimination of junctional nests were common features. Focal active regression of the dermal component was frequently noted but there was no nuclear pleomorphism or dermal mitotic activity. Acral Spitz nevi were characterized by strong and diffuse P16 and P21 expression, which differs from acral nevi and acral lentiginous melanoma. Acral Spitz nevi are a distinctive subgroup of Spitz nevi with benign behavior. Awareness of the subtle histologic differentiating features and the distinctive P16/P21 expression pattern allows separation from melanoma.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".