SAN FRANCISCO Follow-up on 219 patients with Spitz nevi found that 7 (3%) developed malignant melanoma, and in each case the original biopsy showed an atypical or desmoplastic Spitz nevus.
The patients who developed melanoma also were older (aged 34-66 years) at the time the Spitz nevi were diagnosed, compared with patients who did not develop melanoma (whose Spitz nevi appeared predominantly between ages 6 and 30 years), Dr. Lori Prok said at a meeting of the Society for Pediatric Dermatology.
Follow-up of the patients from three clinical sites in Colorado ranged from 1 month to more than 11 years. Many of the Spitz nevi were located on the extremities, especially the lower extremities, "which was a little bit surprising to me," said Dr. Prok, a pediatric dermatopathologist who also handles adult dermatopathology cases at the University of Colorado Hospital, Denver.
Six of the malignant melanomas appeared at different anatomic sites than the Spitz nevus location. One melanoma was re-excised and found to be malignant melanoma in situ. Two patients underwent sentinel node biopsy, with negative results. One patient died of causes unrelated to the tumors.
Dr. Prok and her associates have been studying Spitz nevi to try to better understand the lesion, which histologically shows features of malignant melanoma but is clinically associated with a favorable prognosis. They now are reviewing the charts of the 219 patients to see if the original diagnoses were correct or if melanomas were mistaken for atypical or desmoplastic Spitz nevi. They also will be following these patients for longer-term outcomes.
Dermatopathologists are easily confused by Spitz nevi, as illustrated in a study of 10 dermatopathologists who reviewed 30 melanocytic lesions (including 17 Spitzoid lesions) and were blinded to clinical data and patient outcomes. They were asked to choose a label for each lesion from five categories: Spitz nevus, atypical Spitz nevus, malignant melanoma, neoplasm of uncertain behavior, or other.
Only one case engendered agreement by six or more dermatopathologists. At least seven pathologists scored 13 normal lesions as melanomas, and some fatal lesions were categorized by most of the pathologists as Spitz nevi or atypical Spitz nevi (Hum. Pathol. 1999;30:513-20).
"The take-home message is that the pathologists were just not very good," Dr. Prok said. "It's not that pathologists are stupid, it's that it's really difficult" to categorize Spitzoid lesions.
Physicians also are confused by Spitz nevi because they raise unanswered questions in management. If Spitz nevi really are benign, why did a meta-analysis of 716 Spitz nevi conclude that all Spitz nevi should be completely excised, with re-excision of positive margins (J. Am. Acad. Dermatol. 1993;29:667-8)? How wide should those margins be? One paper suggests 1-cm margins, Dr. Prok noted.
Separate, unpublished data analyzed by two of her associatesa dermatopathologist and a cutaneous oncologist at the universityfound that 100% of patients who were treated for Spitzoid melanomas or melanomas with Spitzoid features or atypical melanoma tumors were disease-free 7 years later. In comparison, around 75% of patients who were treated for classical, unequivocal melanoma were disease-free 7 years later.
Sentinel lymph node biopsies in 57 patients with atypical Spitz tumors were positive in 27 (47%), a separate study found. The patients with positive nodes were younger (an average 18 years old versus 29 years old in node-negative patients) and had good outcomes at a median follow-up of 44 months. All 27 node-positive patients were alive and disease-free at follow-up (Cancer 2009;115:631-41).
The authors concluded that atypical Spitz tumors do not behave like conventional melanoma, and they questioned the role of sentinel lymph node biopsy in managing atypical Spitz nevi.