[508] Immunodetection of Phosphohistone H3 (PHH3) as a Surrogate of Mitotic Figure Count and Clinical Outcome in Cutaneous Melanoma

Michael T Tetzlaff, Jonathan L Curry, David L Stockman, Doina Ivan, Wei-Lien Wang, Karla M Valencia, Roland Bassett, Carlos A Torres-Cabala, Victor G Prieto. University of Texas MD Anderson Cancer Center, Houston, TX

Background: In the AJCC-TNM (2009) staging system, the key prognostic factor in cutaneous melanoma is the depth of dermal invasion (Breslow thickness; BT) with further refinement according to the presence of epidermal ulceration and/or dermal mitoses. Immunodetection of phosphohistone H3 (PHH3) has been shown to facilitate the identification of mitotic figures and to function as a surrogate of outcome in various neoplasms.
Design: We selected 120 cases of primary cutaneous melanoma from our archives (2002-2005) with completely annotated histopathologic parameters and clinical outcomes and performed double immunohistochemical staining for Mart-1 and PHH3. The association between manual mitotic count and PHH3 mitotic count was assessed by Pearson correlation. The association between the presence of metastasis and mitotic counts (manual and PHH3), Breslow thickness, and ulceration was assessed by logistic regression.
Results: 113 cases were amenable to anti-PHH3 staining from 66 men and 47 women with mean age of 64 years (9-93). 61 were superficial spreading type, 24 nodular, 6 lentigo maligna, 8 acral lentiginous, and 14 unclassified. The mean BT was 2.53 mm (0.20-25), ulceration was present in 25/113 lesions (22%) and the mean mitotic count was 3.2/mm2 (<1-29). In 27/113 (24%) of the cases, anti-PHH3 failed to highlight mitotic figures anywhere in the tissue, whereas in 86/113 (76%) anti-PHH3 detected at least 2 mitotic figures somewhere in the tissue (normal and/or tumor cell). Among the latter, anti-PHH3 did not detect mitoses in tumor cells in 37/86 cases (43%) whereas PHH3 identified at least one dermal melanocytic mitotic figure in 49/86 cases (57%; range:1-66). The relationship between PHH3 and manual mitotic count was statistically significant (Pearson correlation=0.59, p<0.0001) with discrepancies identified in 10 cases: anti-PHH3 did not identify mitoses in 6 cases where they were previously identified, and anti-PHH3 detected mitoses in 4 cases previously described as <1/mm2. Logistic regression analyses demonstrated an association between the subsequent development of metastatic disease and the following variables: mitotic figures (odds ratio (OR)=5.7; p=0.0001); PHH3-positive mitotic figures (OR)=3.0; p=0.008); Breslow thickness (OR=4.0 per mm; p=0.0002); ulceration (OR)=3.94; p=0.008).
Conclusions: The application of PHH3 immunohistochemistry to the description of primary cutaneous melanoma greatly facilitates the identification of mitotic figures and correlates with an increased risk for metastasis.
Category: Dermatopathology

Monday, March 4, 2013 11:30 AM

Proffered Papers: Section F, Monday Morning


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