Conversion of a complete hydatidiform mole into choriocarcinoma is indicated by all, EXCEPT:

Suburethral Nodule is an unusual indicator of postmolar choriocarcinoma. All others are very well seen in the conversion of a complete hydatidiform mole into choriocarcinoma. Suburethral nodule may be a manifestation of vaginal metastasis from choriocarcinoma. Metastatic choriocarcinoma is however seen in only about 4% of patients after evacuation of a complete mole and vaginal metastasis that may present with suburethral nodule occur in only 30% of patients with such metastatic disease. Hence it is an unusual indicator. Ref: Novok's, 14th Edition, Page 1588, 1591, 1592 ; William's Gynaecology, 1st Edition, Page 764 ; COGDT, 10th Edition, Page 1890 ; Gynecological Cancer Management : Identification, Diagnosis and Treatment By Daniel Clarke-Pearson, John Soper, 2011.