[1261] Secretory Endometrial Intraepithelial Neoplasia (SEIN) Arising in Secretory Endometrium: Histologic & Immunohistochemical Features of a Rare EIN Variant

Whitney Winham, Kari Hooper, Pam Stone, Charles Quick. UAMS, Little Rock, AR

Background: Diagnosis of EIN in a background of secretory endometrium (SE) is difficult due to gland crowding. In addition, a rare variant of EIN with secretory features has been suggested. In this study, we evaluated the histologic features of this uncommon and difficult to diagnose entity and evaluated the distinction between SEIN and other types of EIN from SE.
Design: 77 endometrial biopsies diagnosed as hyperplasia (all types, WHO criteria) were evaluated using EIN criteria. We searched for cases of possible SEIN, as well as EIN associated with a background of SE. Histologic features (including luminal complexity and cytoplasmic and nuclear features) were evaluated in all cases. PAX2 staining was performed on all available blocks to investigate previous claims that PAX2 may aid in the diagnosis of EIN. PAX2 staining was defined as 3+ (strong nuclear staining, >90% nuclei), 2+ (weak nuclear staining, >50% nuclei), or 1+ (faint nuclear staining, <50% nuclei).
Results: Of the 77 cases, 3 (4%) were classified as SEIN. The defining features included luminal complexity; vacuolated, voluminous cytoplasm; nuclear overlap and vesicular chromatin. SEIN is distinct from SE because the glands are larger, more complex, and haphazardly arranged. Three additional cases were classifed as EIN arising in a background of SE. These lesions were histologically distinct from SEIN because the neoplastic glands lack luminal complexity and resemble proliferative glands, but they arose in a background of SE. Luminal secretions were present in both types of EIN.
Lesional EIN tissue was available for PAX2 staining in 5 cases. All cases of EIN showed altered PAX2 staining compared to background non-neoplastic glands, which are strongly PAX2 positive. Three cases showed negative PAX2 staining in EIN. One case showed increased EIN PAX2 staining compared to the background. The remaining case showed decreased EIN PAX2 staining (2+) compared to normal glands. Five of the six EIN cases were treated with hormones, with negative subsequent samples (rebiopsy or hysterectomy). On follow-up, all EIN cases had no evidence of disease (mean: 7 months).
Conclusions: This is the first detailed description of SEIN, which is an uncommon lesion distinct from traditional EIN, and its distinction from SE using both histologic criteria and PAX2 staining. All EIN (including SEIN) displayed altered PAX2 staining when compared to normal glands, primarily negative or decreased staining. Hormone therapy appears to be effective in treating EIN, although follow-up in this study is short.
Category: Gynecologic & Obstetrics

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 130, Tuesday Afternoon


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