Solid masses of the ovaries raise the suspicion of malignancy or metastasis and require histological diagnosis. Extramedullary haematopoesis (EMH) is a rare histological finding of a mass of the adnexa. The sonographic pattern of EMH has rarely been described in the literature. Transvaginal biopsy of EMH has not been reported in the literature. We present a case of adnexal EMH in a patient affected with β-thalassaemia, and we performed a narrative review. Only in our case, the sonographic pattern was described, and a transvaginal ultrasound-guided core biopsy was used. Assessing patients’ medical history and correlating it to the findings of diagnostic imaging is of paramount importance when evaluating patients with adnexal masses. The correct interpretation of sonographic images can avoid unnecessarily invasive procedures. A transvaginal biopsy could be a safe, easy and well-tolerated method to gain definite histological diagnosis in cases where a primary ovarian malignancy is not suspected.