Most patients have good prognosis, with only minority of cases progressing to systemic disease or death
Microscopic
• Severely atypical/borderline Spitz tumor
Typically, large and deep cellular compound melanocytic tumors
May appear symmetric and well circumscribed at low power
Cells show severe cytologic atypia with nuclear hyperchromasia, enlarged nucleoli, irregular chromatin, and abundant amphophilic or dense eosinophilic cytoplasm
Mitotic figures often present, increased compared to conventional Spitz nevi
• Spitzoid melanoma
Also large and deep tumors
Frank atypia and pleomorphism present
Junctional component often shows irregular nesting, confluence, and prominent pagetoid upward scatter
Multiple mitotic figures usually present
Often atypical &/or deep
Clinical Photograph of Atypical Spitz Tumor This is an atypical compound Spitz tumor on the buttock of a 16-year-old patient. Despite the clinically banal appearance, there was severe cytologic atypia and multiple dermal mitotic figures identified, histologically.
Severely Atypical Spitz Tumor This severely atypical compound Spitz tumor shows a predominantly intradermal population of atypical spindled cells with nuclear enlargement, hyperchromasia , and focally prominent nucleoli.
Spitzoid Melanoma This is an example of spitzoid melanoma in a young adult. The dermal cells are markedly enlarged, atypical, and pleomorphic appearing. In addition, there are multiple mitotic figures in this field .
HMB-45 Immunohistochemistry in Spitzoid Melanoma This spitzoid melanoma shows strong HMB-45 staining in the dermis. Although not always positive, strong dermal HMB-45 expression in an atypical melanocytic proliferation should raise suspicion for melanoma.
TERMINOLOGY
Abbreviations
• Atypical Spitz tumor (AST)
Synonyms
• Atypical spitzoid melanocytic proliferation
• Spitz tumor of borderline/uncertain malignant potential
• Spitzoid melanoma
Definitions
• Atypical/borderline Spitz tumor: Severely atypical melanocytic proliferation with features intermediate between Spitz nevus and spitzoid melanoma
• Malignant Spitz tumor: Malignant melanocytic proliferation with spitzoid features
ETIOLOGY/PATHOGENESIS
Unknown
• Typically occur in young patients without any known risk factors for melanoma
• Sun exposure may be risk factor in some cases
Possible Genetic Role
• Suggested by chromosome 11p amplification in minority of Spitz nevi
• Complex chromosomal alterations typically seen in melanoma
CLINICAL ISSUES
Epidemiology
• Incidence
Very rare tumors
• Age
Mostly young patients; range: 2-30 years
Malignant tumors more common in postpuberty
Presentation
• Dermal papule or nodule
Treatment
• Surgical approaches
Complete and wider excision is standard therapy
– Typically ≥ 5-mm clinical margins for atypical/borderline tumors
– Spitzoid melanomas should be treated with same margins as invasive melanomas of same Breslow depth
Sentinel lymph node biopsy remains controversial
– Should be considered prognostic rather than therapeutic procedure at this time
– Controversial but likely should not be routinely used (especially for atypical/borderline tumors) until validated by more extensive clinical studies
Prognosis
• Difficult to predict
Most patients have relatively good prognosis, with only minority of cases progressing to metastasis and death
Even patients with lymph node involvement often have relatively good prognosis, as most tumors do not disseminate further
MICROSCOPIC
Histologic Features
• Severely atypical/borderline Spitz tumor
Typically, large and deep cellular compound tumor
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, and focally prominent nucleoli.
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