What is the recommended management if a lesion contains pagetoid cells and Kamino bodies with no loss of P16?

Management of a Lesion with Pagetoid Cells and Kamino Bodies with No Loss of P16

A lesion containing pagetoid cells and Kamino bodies with preserved p16 expression should be managed as an atypical Spitz tumor requiring conservative re-excision with 2-5 mm margins and long-term clinical follow-up. 1

Diagnostic Considerations

The presence of pagetoid cells (cells that migrate upward into the epidermis) along with Kamino bodies (eosinophilic globules) and preserved p16 expression creates a specific diagnostic profile that helps distinguish this lesion from more aggressive entities:

• Pagetoid cells: While concerning as they can be seen in melanoma, pagetoid spread is also found in 55% of benign Spitz nevi, particularly when centrally located 2
• Kamino bodies: These eosinophilic globules are typically associated with Spitz nevi and are considered a benign feature 2
• Preserved p16 expression: This is a crucial finding, as complete loss of p16 is associated with more aggressive lesions 3

Recommended Management Algorithm

1. Complete histopathological assessment:

   • Evaluate for concerning features: asymmetry, high-grade cytological atypia, deep dermal mitoses, ulceration, lack of maturation 1
   • Confirm p16 expression status (already noted as preserved)
   • Assess HMB45 expression pattern (loss of expression with depth indicates maturation)
   • Perform dual-color Ki67/MART-1 immunohistochemistry to evaluate proliferation 3

2. Molecular/cytogenetic testing:

   • Consider FISH testing for chromosomal aberrations (6p25, 8q24, 11q13, centromere 9, and 9p21) 3
   • If FISH results are negative or equivocal, consider array-based comparative genomic hybridization (aCGH) 3

3. Surgical management:

   • Perform conservative re-excision with 2-5 mm margins 1
   • This approach ensures complete removal while minimizing excessive scarring

4. Follow-up:

   • Implement regular clinical follow-up with baseline photography documentation 1
   • Long-term monitoring is essential even after complete excision

Clinical Reasoning

The preserved p16 expression is particularly significant in this case. According to modern diagnostic algorithms for atypical spitzoid tumors, complete loss of p16 expression is associated with homozygous deletion of 9p21, which correlates with more aggressive behavior 3. The presence of p16 expression indicates that this lesion likely has a more favorable prognosis.

The combination of pagetoid cells with Kamino bodies creates a diagnostic challenge, as these features can be seen in both benign Spitz nevi and melanoma. However, the preserved p16 expression tips the balance toward a more favorable diagnosis 3, 1.

Potential Pitfalls to Avoid

• Overtreatment: Treating as melanoma would lead to unnecessarily wide excision margins (1-2 cm) 3 and potential sentinel lymph node biopsy
• Undertreatment: Simple observation without re-excision could miss progression in atypical lesions
• Misdiagnosis: Relying solely on histopathology without molecular testing can lead to diagnostic errors due to overlap between atypical Spitz tumors and melanoma 1
• Inadequate follow-up: These lesions require long-term monitoring even after complete excision 1

By following this evidence-based approach, you can ensure appropriate management while avoiding unnecessary aggressive treatment for this lesion with specific histopathological features.