Neuropilin-2 as a useful marker in the differentiation between Spitzoid malignant melanoma and Spitz nevus.

BACKGROUND: Spitzoid malignant melanoma (SMM) shares many histopathologic features with Spitz nevus (SN). The distinction between SMM and SN remains one of the most difficult diagnostic problems in dermatopathology. Neuropilin-2 (NRP2) is a cytoplasmic/cell surface protein that is a mediator of melanoma-endothelial cell interaction. OBJECTIVE: The aim of this study was to evaluate NRP2 expression in SMM and SN and to determine whether it can reliably differentiate between the 2 groups. METHODS: We studied the expression of NRP2 in 19 cases of SMM and 19 cases of SN from Yale Spitzoid Neoplasm Repository, New Haven, Conn. RESULTS: All 19 cases of SMM (100%) expressed NRP2. Most SMM showed moderate- and high-intensity staining in the majority of the melanoma cells. Most of the SN (14/19, 74%) were negative for the marker. NRP2 labeled only 5 of 19 SN (26%) and all of them demonstrated mild staining intensity. NRP2(+) staining was statistically significant in differentiating SMM from SN (P < .05). LIMITATIONS: Small study size is a limitation. CONCLUSIONS: NRP2 expression in SMM and SN may be a useful adjunct marker, in addition to histopathologic evaluation, in the differentiation between these 2 entities.

Detecting HPV in cutaneous lesions using anti-HPV antibody immunohistochemistry.

Most condyloma are diagnosed clinically (without a biopsy) or histopathologically (if biopsied) without any ancillary testing. In some cases, additional confirmation of productive infection by human papillomavirus (HPV) or typing of HPV is desired, and in situ hybridization (ISH) is the most commonly used test. However, ISH is not readily available in most laboratories and only detects certain genital subtypes of HPV. The aim of this study was to evaluate the sensitivity and specificity of an anti-HPV antibody, in 25 lesions (both HPV induced and non-HPV induced) mostly from the genital region, with comparison to results with ISH and findings on hematoxylin and eosin staining. The sensitivity and specificity for the anti-HPV antibody used in this study are 90.9% and 85.7%, respectively, compared with ISH. Immunohistochemistry with this anti-HPV antibody, like ISH, was generally positive in cases showing koilocytes/koilocytotic atypia (86%). Immunohistochemical staining also detected productive infection with HPV in 23% (3 of 13) of cases without koilocytes/koilocytotic atypia. Thus, although staining is generally positive in cases with diagnostic findings of koilocytes/koilocytotic atypia in hematoxylin and eosin sections, immunohistochemistry can detect HPV in some cases without koilocytes/koilocytotic atypia.

Expression of p16 alone does not differentiate between Spitz nevi and Spitzoid melanoma.

BACKGROUND: Spitz nevi and Spitzoid melanomas show overlapping histopathologic features, often making the diagnosis challenging. The p16 protein functions as a tumor suppressor and loss of its expression may be seen in some melanomas. METHODS: We evaluated 18 Spitz nevi and 19 Spitzoid melanomas from the Yale Spitzoid Neoplasm Repository for p16 expression. A staining intensity score (SIS) was calculated by multiplying a score for the percentage of stained cells (0-3) by a score for staining intensity (0-3). RESULTS: Staining with p16 was positive in 15/18 (83%) Spitz nevi and 15/19 (79%) Spitzoid melanomas (p = 0.73). Both Spitz nevi and Spitzoid melanomas had a similar SISs, 4.9 and 3.8, respectively (p = 0.057). All 19 patients with Spitzoid melanomas had poor outcome with either death (6 patients) or metastases (13 patients) at a median (3 years) and mean (5.4 years) follow up. In contrast, all 18 patients with Spitz nevi had a benign course with no adverse events at a median (4 years) and mean (4 years) follow up. CONCLUSIONS: We found no significant difference in p16 staining in Spitz nevi and Spitzoid melanomas. We conclude that p16 does not appear to be a useful immunohistochemical marker in distinguishing between Spitz nevi and Spitzoid melanomas.