What is the recommended management approach for atypical spitz nevus?

Management of Atypical Spitz Nevus

The recommended management for atypical Spitz nevus is conservative re-excision with narrow margins (1 cm) and long-term follow-up due to its uncertain malignant potential. 1

Diagnostic Approach

Atypical Spitz nevi represent challenging melanocytic lesions that display features of both benign Spitz nevi and spitzoid melanomas. Accurate diagnosis requires a systematic approach:

1. Histological evaluation

   • Key melanoma-suggesting features to assess 1:
     • Asymmetry
     • Lack of circumscription
     • Lack of maturation in dermis
     • Ulceration
     • Deep dermal mitoses
     • Frequent/atypical mitoses
     • High-grade cytological atypia
     • Brisk lymphocytic infiltrate

2. Immunohistochemical assessment

   • Critical markers 1:
     • Ki67/MART-1 dual staining (to assess deep dermal proliferation)
     • p16 expression (complete loss suggests melanoma)
     • HMB45 expression pattern

3. Molecular/cytogenetic testing

   • FISH with five probes (6p25, 8q24, 11q13, centromere 9, 9p21) 1
   • Array-based comparative genomic hybridization (aCGH) for comprehensive chromosomal evaluation 1

Surgical Management

The surgical approach depends on diagnostic findings:

• For confirmed atypical Spitz nevus (negative or non-melanoma pattern on FISH/aCGH):

  • Conservative re-excision with 1 cm margins is recommended 1
  • This applies particularly to children under 14 years 1

• For lesions with melanoma-pattern chromosomal aberrations:

  • Treat as spitzoid melanoma with appropriate melanoma margins 1

Sentinel Lymph Node Biopsy Considerations

• SLNB should be considered for atypical Spitz tumors ≥1 mm in thickness 1
• Despite high rates of positive SLNBs in atypical Spitz tumors (47%), local recurrence is rare 1
• SLNB provides valuable staging information and helps clarify metastatic potential 1

Follow-up Recommendations

• Long-term clinical follow-up is essential for all patients with atypical Spitz nevi 1
• More intensive surveillance is warranted for lesions with:
  • Positive margins after initial biopsy
  • Multiple concerning histologic features
  • Equivocal molecular findings

Special Considerations

Age-Related Management

• Young children (<14 years): 1 cm margins regardless of thickness 1
• Older children/young adults: Margins based on thickness per melanoma guidelines 1

Biopsy Technique Impact

• All biopsy techniques (shave, punch, excision) have high rates of positive margins with Spitz lesions 2
• Complete excisional biopsy is preferred when Spitz lesion is suspected 1

Common Pitfalls to Avoid

1. Underestimating atypical lesions: Even with benign molecular findings, atypical Spitz nevi require complete excision and follow-up
2. Over-reliance on single diagnostic modality: Integration of clinical, histological, immunohistochemical, and molecular findings is essential
3. Inadequate margins: Incomplete excision may lead to recurrence and diagnostic uncertainty
4. Lack of follow-up: These lesions require long-term monitoring due to uncertain biological behavior

The management of atypical Spitz nevi remains challenging due to their unpredictable biological behavior, but a systematic diagnostic approach and appropriate surgical management with long-term follow-up offers the best outcomes for patients.