The atypical Spitz tumor of uncertain biologic potential

I read with interest the recent article by Ludgate et al, who reported on a large series of atypical Spitz tumors (ASTs), a subgroup of ambiguous tumors that have histologic features of Spitz nevi mixed with features of melanoma and, thus, are difficult to diagnose. In such patients, sentinel node biopsy has been proposed with the hypothesis that, if any metastasis is detected, then it represents proof that the lesion was malignant. To date, 117 patients with ASTs who underwent sentinel node biopsy have been reported, and 50 of those patients had lymph node lesions. Such melanocytic deposits have been interpreted mostly as micrometastases; however, because the possibility that they represent only benign nevi also was considered, the consequent discussion developed by the authors on this topic risks diminishing the possible diagnostic value of sentinel node biopsy in patients with these tumors. Undoubtedly, the incidence of melanocytic deposits in sentinel lymph nodes from patients with ASTs (42.7%) differs dramatically from that of lymph node nevi in sentinel lymph nodes from patients with melanoma (3.9%). However, because diagnostic criteria with which to differentiate lymph node micrometastases from lymph node nevi exist and seem to work, all lymph node lesions should be diagnosed using the same histologic criteria, irrespective of the diagnoses made on synchronous cutaneous tumors. In fact, it does not seem reasonable to diagnose a lymph node lesion as metastasis if the cutaneous lesion was labeled as melanoma and to diagnose a lymph node lesion that has the same characteristics differently if the cutaneous tumor was classified otherwise. If to diagnose a cutaneous tumor using data derived from a lymph node is illogical, then, in the same way, it must be illogical to use data derived from a cutaneous tumor to diagnose a lymph node lesion.