Atypical Spitzoid melanocytic tumors: A morphological, mutational, and FISH analysis

Background: Identification of the clinical behavior of atypical Spitzoid tumors with conflicting histopathologic features remains controversial. Objective: We sought to assess whether molecular findings may be helpful in the diagnostic and prognostic assessment of atypical Spitzoid tumors. Methods: A total of 38 controversial, atypical Spitzoid lesions (≥1 mm in thickness) were analyzed for clinicopathological features, chromosomal alterations by fluorescence in situ hybridization (FISH) analysis (RREB1/MYB/CCND1/CEP6), BRAF^V600E mutation by allele-specific real-time polymerase chain reaction confirmed by sequencing, and H-RAS gene mutation by direct sequencing. Results: Atypical Spitzoid lesions developed in 21 female and 17 male patients (mean age 22 years). Nine patients underwent sentinel lymph node biopsy and a sentinel lymph node micrometastasis was detected in 4 of these 9 cases. Four additional patients, who did not receive a sentinel lymph node biopsy, experienced bulky lymph node metastases and one experienced visceral metastases and death. Lesions from patients with lymph node involvement showed more deep mitoses (P <.01), less inflammation (P = .05), and more plasma cells (P = .04). FISH analysis demonstrated the presence of chromosomal alterations in 6 of 25 cases. Correlation with follow-up data showed that the only case with fatal outcome showed multiple chromosomal alterations by FISH analysis. BRAF ^V600E mutation was detected in 12 of 16 cases (75%) and H-RAS mutation on exon 3 was found in 3 of 11 cases (27%). Limitations: Our results require validation in a larger series with longer follow-up information. Conclusions: FISH assay may be of help in the prognostic evaluation of atypical Spitzoid tumors. Diagnostic significance of BRAF^V600E and H-RAS mutations in this setting remains unclear.