[1126] Malignant Struma Ovarii: A Study of 86 Cases Demonstrating No Correlation between Pathological Features and Disease Course.

Ruthy Shaco-Levy, Ruth Peng, Matthew M Snyder, Sarah M Bean, Stanley J Robboy. Soroka University Medical Center, Beer-Sheva, Israel; Duke University Medical Center, Durham, NC

Background: Struma ovarii that exhibit malignant histology is very uncommon, and aggressive clinical course in the form of initial extra-ovarian spread or later recurrence is even more exceptional for these tumors. This study analyzes in detail the morphological features of 86 histologically proliferative (adenoma-like) or histologically malignant struma ovarii cases that with many years of follow-up proved to be biologically benign or malignant, in an attempt to define if specific histological features have predictive value.
Design: Microscopic analysis in two categories (absence or presence ≤10% vs. presence >10% tumor) was performed for the following criteria: papillary architecture, pseudo-papillae, psammoma bodies, nuclear grooves, nuclear overlap, "orphan Annie" nuclei, nuclear pseudo-inclusions, nucleoli, hypercellularity, colloid scalloping, and nuclear pleomorphism. A qualitative analysis was performed for the absence or presence of vascular and capsular invasion. Fibrosis was categorized to four groups: absent, peripheral, central, or peripheral and central. Cell size was divided to three groups: large, normal, and small. Three cell types were recognized: regular, oxyphilic, and clear. Tumor architecture was classified according to the prevalent pattern as microfollicular, macrofollicular, and trabecular. For mitotic activity the number of mitoses per 10 high power fields (HPF) was stated. We examined if specific histological features are associated with malignant clinical course.
Results: The patients were 4 to 61 years old (median=41 years). Twenty-six cases were biologically malignant; among them 8 (31%) were histologically malignant as well, and 18 (69%) were histologically proliferative. Of the 60 biologically benign cases, 17 (28%) displayed malignant histology, and 43 (72%) were histologically benign. Furthermore, the probability of a malignant clinical course was around 30% in cases with either benign or malignant histology. The presence of all the histological features examined was similar in the biologically benign and malignant tumors. No specific histological feature was found to be predictive of an aggressive clinical course.
Conclusions: The clinical outcome of struma ovarii cannot be predicted based on the microscopic diagnosis of the thyroid tissue or on specific histological features. The lack of correlation between morphology and outcome in proliferative and histologically malignant struma ovarii is striking, making the behavior of these tumors particularly unpredictable.
Category: Gynecologic & Obstetrics

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 126, Tuesday Afternoon

 

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