Expression of D2-40, a Marker of Mesothelial and Lymphatic Endothelial Differentiation, in Adenomatoid Tumors: A Potential Diagnostic Pitfall in Distinguishing from Lymphatic Tumors
SJ McAlhany, JT Rabban. University of California San Francisco, San Francisco, CA
Background: Adenomatoid tumors are benign tubulo-glandular proliferations of mesothelial immunophenotype (calretinin, WT-1 positive) that commonly involve the female and male genital tract. Though diagnosis is usually straightforward, the differential diagnosis may include Sertoli cell tumor, yolk sac tumor, adenocarcinoma, or lymphangioma/lymphangioleiomyoma, depending on the anatomic site. Because calretinin and WT-1 expression may overlap with some of these entities, we hypothesized that the novel mesothelial marker D2-40 may be of value in evaluating adenomatoid tumors. However, because D2-40 also reacts with lymphatic endothelium, we tested D2-40 expression in lymphatic tumors arising in similar anatomic sites to determine its specificity in this differential diagnosis.
Design: Immunohistochemical staining for D2-40 (Dako, 1:50), calretinin (Zymed, 1:200), and WT-1 (Dako, 1:200) was performed on 33 adenomatoid tumors (17 uterine, 6 fallopian tube, 9 paratesticular, 1 scrotal). Staining for each of these markers was also performed in 19 lymphangiomas (8 retroperitoneal, 5 omental/mesenteric, 2 mediastinal, 2 abdominal wall, 1 subcutaneous, 1 unknown origin), and 1 case of uterine lymphangioleiomyomatosis. Nuclear staining for calretinin or WT-1 was defined as positive. Cytoplasmic staining for D2-40 was defined as positive.
Results: Thirty-one of 33 (94%) adenomatoid tumors expressed D2-40 and calretinin, while 26 of 33 (79%) expressed WT-1. The staining pattern was strong and diffuse in the tumor cells for both D2-40 and calretinin, while staining for WT-1 was focal and weaker in intensity. Eighteen of 19 lymphangiomas showed diffuse and strong expression of D2-40 but no expression of calretinin or WT-1. The lymphatic component of the lymphangioleiomyoma case demonstrated strong D2-40 expression but no staining for calretinin or WT-1.
Conclusions: Adenomatoid tumors strongly expressed D2-40. This can be of value when the differential diagnosis includes tumors that also express WT-1 or calretinin. However, since D2-40 was also expressed in lymphatic tumors, caution is warranted in relying on this marker alone and a broad panel of mesothelial and lymphatic markers should be considered.
Tuesday, March 10, 2009 1:00 PM
Poster Session IV # 166, Tuesday Afternoon