The dermal-based borderline melanocytic tumor: a categorical approach.

Background: The borderline melanocytic tumor (BMT) is a morphologically and biologically indeterminate melanocytic proliferation manifesting worrisome architectural features and cytologic atypia exceeding that encountered in melanocytic nevi yet insufficient to warrant designation as melanoma. The criteria that define the BMT are not well defined nor is the concept widely recognized.

Objective: The purpose of this study is to provide a practical framework for the approach to the dermal BMT.

Methods: Thirty-two patients with BMTs extending into the reticular dermis and at a depth of 0.75 mm or more underwent local excision and sentinel lymph node biopsy between 2000 and 2006. Four categories of BMT were recognized: (1) nevoid BMT (BNM); (2) the atypical Spitz tumor (AST); (3) pigmented epithelioid melanocytoma (PEM); and (4) BMT arising in a deep penetrating nevus (B-DPN).

Results: Four patients were in the BNM category (male/female ratio [M:F] = 1:3; mean age = 27 years, range = 15-36), 14 in the AST category (M:F = 7:7; mean age = 20.9, range = 3-58), 7 in the PEM category (M:F = 4:3; mean age = 23.5, range = 3-39), and 7 in the B-DPN category (M:F = 5:2; mean age = 22.3, range = 14-36). The percentages of patients with positive sentinel nodes in each category were 25% (1/4), 35% (5/14), 14% (1/7), and 57% (4/7), respectively. The average time of follow-up was approximately 4.2 years. One patient, a 36-year-old man, died of disease, while the others are alive and well. In the one death attributable to widespread metastatic disease, the lesion was initially interpreted as a deep penetrating nevus; however, retrospective review revealed features compatible with a B-DPN; the review was prompted by a recurrence that was morphologically compatible with a Clark level V malignant melanoma, reflecting clinical and morphologic progression.

Limitations: The mean follow-up was less than 5 years. Molecular studies to further explore the biologic commonality with melanoma were not performed.

Conclusion: The dermal variant of BMT is a tumor of younger adults and children that can be associated with lymph node disease and a potential for morphologic and biologic progression when inadequately treated.