Superficial Micronodules of Pregnancy (SMOPs) and MIB-1 (Ki-67) Proliferation Index in Benign Nevi Excised during Pregnancy
MP Chan, MM Chan, SR Tahan. Beth Israel Deaconess Medical Center, Boston, MA
Background: The clinical appearance of benign nevi can dramatically change during pregnancy, leading to concern for malignant transformation and excisional biopsy. Because the hormonal milieu of pregnancy has not been shown to alter the banal behavior of these nevi, histologic characterization is needed to prevent overdiagnosis and unnecessary treatment. In this study we evaluate the histology of banal nevi removed during pregnancy, assess proliferative activity, and identify distinct histologic features.
Design: Dermal nevi excised from pregnant women during the second and third trimesters (n=10) were compared with location- and aged-matched controls (n=10) in a blinded manner. Immunohistochemical stain for MIB-1 (Ki-67) was performed on paraffin sections. A unique histologic entity is describedsuperficial micronodules of pregnancy (SMOPs)as cytologically distinctive rounded clusters of plump epithelioid melanocytes with abundant cytoplasm and prominent nucleoli, present in the superficial aspect of the nevus. Other features including mitoses, multinucleated melanocytes, and pigmentation (graded from 0-3) were also examined.
Results: The average age (32.2 2.4 and 29.5 5.6 years, pregnant vs. control, respectively) and nevic location (trunk, head and neck) are similar between groups. Intraepidermal cytologic atypia is minimal. Histologic features are summarized below:
|# Dermal mitoses /10 hpf||MIB-1 (% positive)||Presence of SMOPs||Multinucleated melanocytes||Amount of pigmentation|
|Pregnant (n=10)||2.5 (1.96)||3.5 (3.66)||8/10||0/10||1.3|
|Control (n=10)||0.2 (0.63)||1.0 (1.8)||3/10||5/10||1.1|
Benign dermal nevi excised during pregnancy have increased mitotic figures, are more likely to have SMOPs, and lack multinucleated dermal melanocytes. There is a trend towards higher MIB-1 activity in the nevi of pregnancy, although not statistically significant.
Conclusions: Benign dermal nevi of pregnancy demonstrate characteristic histologic features including superficial micronodules of pregnancy (SMOPs), increased dermal mitotic figures, and increased MIB-1 proliferation index. The disproportional increase in observed mitotic figures compared to MIB-1 may suggest a hormonal effect on cell cycle regulation.
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 50, Wednesday Morning