Ans. is a, i.e. DysgerminomaRef: Bailey & Love 24th/ed, p22l"Below the age of 20 years 60% of the tumors are of germ cell origin and in girls under the age of 10 years almost 85% are of germ cell origin and are invariably malignantIn females with HNPCC gene mutation along with BSO, hysterectomy should also be done as there is an associated risk of endometrial cancer. In BRCA gene mutation Hysterectomy is not routinely recommended.RememberThe most common malignant GCT Earlier was dysgerminoma but now its incidence has declined & it is the second most common malignant GCT."Because their incidence has declined by approximately 30 percent over the past few decades, dysgenia accurately accounts for only approximately one third of all malignant ovarian germ cell tumors." - Ref: Williams Gynae 3/ed, p762"Due to a 60 percent increased incidence during the past few decades, immature teratomas are now the M/C variant & account for 40-50% of all malignant ovarian germ cell tumors." - Ref: William gynae 3rd/ed, p765Most common germ cell tumor of ovary is dermoid cyst (mature teratoma). It is benign in nature.Remember:* Most common ovarian tumor (overall) - Epithelial cell tumor.* Most common tumor in young woman is - Germ cell tumor. - Ref: Shaw 14th/ed, p555* Most common malignant tumor of ovary - Serous cystadenocarcinoma.* Most common benign tumor of ovary (overall) - Dermoid cyst. - Ref Williams Gynae 1st/ed, p219* Most common benign epithelial tumor of ovary - Serous cystadenoma. - Ref: Jeffcoate 7th/ed, p531* Most common germ cell tumor - Mature teratoma (Dermoid cyst).* Most common malignant GCT - Immature teratoma > Dysgerminoma. - Ref: Williams Gynae 3/e p765* Most common ovarian tumor in pregnancy (but in remains undiagnosed) - Serous cystadenoma.* Most Common benign tumor diagnosed in pregnancy - Dermoid cyst.* Overall most common ovarian tumor diagnosed in pregnancy - Dermoid cyst.* Most common malignant ovarian tumor detected during pregnancy - Dysgerminoma.* Germ cell Tumor with best prognosis - Dysgerminoma* Germ cell tumor with worst prognosis - endodermal sinus tumor* Germ cell tumor which has maximum bilaterality - Dysgerminoma* Germ cell tumor which presents as acute abdomen - Endodermal Sinus Tumor* Most common ovarian tumor to undergo torsion during pregnancy - Dermoid cyst.* Most common ovarian tumor to involve opposite ovary by metastasis - Granulosa cell tumor.* Most radiosensitive ovarian tumor - Dysgerminoma.. - Ref: Bailey & Love 24th/ed, p221* Most rapidly growing ovarian tumor - Yolk sac Tm- (Endodermal Sinus Tumor)Ovarian Tumor: Causing:* Pseudomyxoma peritonei- Mucinous cystadenoma/Micinous cystadenocarcinoma* Meigs syndrome- Ovarian fibroma* Pseudomeig's syndrome:- Brenner's tumor- Granulosa cell tumor- Thecoma* Ovarian tumor associated with hyperpyrexia and hypercalcemia- Mesonephroid tumor.* Ovarian tumor arising from epithelium of urinary tract- Brenner Tm* Feminizing tumors:- Granulosa cell tumor- Theca cell tumor- Fibromas* Virilising tumor:- Androblastoma- Hilus cell Tm- Gynadroblastoma- Adrenal cortical tumor* Largest benign ovarian tumor- Mucinous cyst adenoma* Tumor with lymphocytic infiltration:- Dysgerminoma.