Pediatric spitzoid lesions of the ear: a single-center experience and review of the literature

Spitzoid lesions are challenging melanocytic lesions comprising benign, intermediate, and malignant lesions. In this study, we aimed to analyze the diagnostic accuracy of clinical and dermatoscopical evaluations of pediatric spitzoid ear lesions. We collected and analyzed, clinically, dermatoscopically, and histologically, pediatric spitzoid ear lesions. We also conducted a systematic review of the literature. At the Pediatric Hospital Gaslini, excision and histopathological evaluation were performed on eight cases: 87.5% of the lesions were consistent with Spitz nevus (SN), and 12.5% with atypical Spitz tumor (AST). Notably, multiple (≥2) dermatoscopical irregularities were present in 5 of 7 SN (71%), yet none were found in AST (0%, 0/1) (Fisher's exact test, P=0.375). From systematic research in the literature, 9 patients were included in this review. At histology, 88.9% were SN and 11% AST. Remarkably, also in the literature, multiple dermatoscopical irregularities were present in most SN (75%, 6/8), but not in the identified AST (0%, 0/1) (P=0.3333). We present a monocentric study on pediatric spitzoid ear lesions. Importantly, dermatoscopical irregularities were not significantly associated with AST, neither in our series nor in the reviewed literature (respectively P=0.375 and P=0.3333), supporting the fact that relying only on the dermatoscopical aspect of spitzoid lesions is not accurate enough for the special site of the ear, where dermatoscopy could actually be misleading.

NTRK Gene Fusion Detection in Atypical Spitz Tumors

Atypical Spitz tumors (AST) deviate from stereotypical Spitz nevi for one or more atypical features and are now regarded as an intermediate category of melanocytic tumors with uncertain malignant potential. Activating NTRK1/NTRK3 fusions elicit oncogenic events in Spitz lesions and are targetable with kinase inhibitors. However, their prevalence among ASTs and the optimal approach for their detection is yet to be determined. A series of 180 ASTs were screened with pan-TRK immunohistochemistry and the presence of NTRK fusions was confirmed using FISH, two different RNA-based NGS panels for solid tumors, and a specific real time RT-PCR panel. Overall, 26 ASTs showed pan-TRK immunostaining. NTRK1 fusions were detected in 15 of these cases showing cytoplasmic immunoreaction, whereas NTRK3 was detected in one case showing nuclear immunoreaction. Molecular tests resulted all positive in only two ASTs (included the NTRK3 translocated), RNA-based NGS and real time RT-PCR were both positive in three cases, and FISH and real time RT-PCR in another two cases. In seven ASTs NTRK1 fusions were detected only by FISH and in two cases only by real time RT-PCR. The frequency of NTRK fusions in ASTs is 9%, with a clear prevalence of NTRK1 compared to NTRK3 alterations. Pan-TRK immunohistochemistry is an excellent screening test. Confirmation of NTRK fusions may require the use of different molecular techniques.