[473] The Utitily of Nestin and Sox2 Immunostains in Distinguishing Desmoplastic Melanoma and Dermatofibrosarcoma Protuberans from Excision Scar

Pei-Ling Chen, Wei-Shen Chen, Jianping Li, Anne C Lind, Dongsi Lu. Washington University School of Medicine, St. Louis

Background: The evaluation of re-excision specimen for residual desmoplastic melanoma (DM) and dermatofibrosarcoma protuberance (DFSP) is a common practice in pathology but is often complicated by the presence of scar tissue. DM is a rare variant of melanoma (MM) that is often amelanotic and neurotropic, and DFSP is a locally aggressive spindle cell tumor of low to intermediate grade malignancy. DFSP has a tendency to local recurrence but rarely metastasizes, and DM is also notoriously recurrent, especially in the presence of neurotropism in original lesion, likely reflecting incomplete excision. Re-excision is often performed after initial excision to ensure no neoplastic cells remain. However, the evaluation of re-excision specimen for residual DM and DFSP can be diagnostically challenging due to the presence of admixed fibroblasts, histiocytes and cells with nuclear atypia in scar tissue, all of which can morphologically mimic DM and DFSP. It has recently been shown that the embryonic stem cell marker Nestin is strongly expressed in MM and DFSP. Sox2, one of the key transcription factors in maintaining pluripotency of stem cells, binds the enhancer region of Nestin and is also expressed in MM. In this study, we sought to test the diagnostic utility of Nestin and Sox2 in differentiating DM and DFSP from re-excision scar.
Design: A total of 40 specimens were retrieved from our archives, including: 14 MM (7 pure DM; 7 spindle cell melanoma [SCM] with DM features), 8 DFSP and 23 scar (5 from above MM cases). Immunostains were performed on FFPE tissue sections using anti-Nestin and anti-Sox2 antibodies.
Results: Cytoplasmic Nestin and nuclear Sox2 were strongly positive in 12 MM (86%). There was weak Nestin in 1 (7%) and negative Sox2 in 2 cases (14%). Nestin highlighted majority of DFSP (n=7/8), while nuclear Sox2 was absent in DFSP. Of all the scar tissue tested, both Nestin and Sox2 were negative. Even though Nestin also highlighted vascular endothelial cells, the staining pattern of vasculature was readily distinguishable from tumor cells. Of note, in 1 DM re-excision specimen that was originally diagnosed as dermal scar, Nestin and Sox2 strongly highlighted one focus of spindle cells with malignant nuclei. Subsequent evaluation of this focus on H&E section confirmed that this represented residual DM.
Conclusions: We demonstrated that the embryonic stem cell marker Nestin is a highly reliable markers in distinguishing DM and DFSP from excision scar. In addition, Sox2 is strongly expressed by DM and can differentiate it from excision scar as well.
Category: Dermatopathology

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 96, Tuesday Morning


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