Appendix-like morphology in primary ovarian mucinous tumors lacking a concurrent mature teratoma: A series of 4 cases illustrating the utility of STR analysis.

Recently in this journal, Ramalingam et al described the clinicopathological features of mucinous ovarian tumors arising in association with mature cystic teratomas (MT). Of particular interest to us are the appendix-like histological features including prominent subepithelial stromal clefts and pseudomyxoma ovarii described by Ramalingam et al and others. In our own practice, we have encountered a handful of mucinous ovarian tumors with the above-noted histological features for which no MT and no appendiceal tumor could be found, leaving the tumors' origin in question. Here we share our experience using short tandem repeat (STR) analysis in order to address this very scenario using 4 illustrative cases. Using STR analysis, we show that the above-noted histological features may indeed suggest a teratomatous origin even in the absence of a histologically apparent MT. We also show that these same histological features may be seen in bona fide primary ovarian mucinous tumors that have a purely somatic origin.