STUMP - atypical leiomyoma of low risk of recurrence – a mimiker of malignant tumor?

Abstract

This study describes the ultrasound diagnostic process and management in a patient with a unique, rare form of fibroids, i.e. the atypical variant. According to the WHO definition, an atypical uterine myoma cannot be histologically unambiguously diagnosed as benign or malignant. Atypical leiomyomas are characterized by moderate or high quantity of pleomorphic atypical tumor cells, with a small number of mitotic divisions and lack of coagulative necrosis in the tumor. They have a low rate of extrauterine, intraabdominal recurrence, with a negligible risk for distant metastases. Due to the fact the atypical variant of leiomyomas is very rare, it presents a significant diagnostic challenge for obstetricians. The most reliable diagnosis can be made only on the basis of the histopathological examination. In this paper, we present a case of a patient in whom an echo with the diameter of 92 mm and a heterogeneous echogenicity with visible anechoic fields were discovered in the uterine fundus. HD color Doppler demonstrated high vascularization within the tumor, peripherally as well as centrally. The peripheral and central vascularization was rated at 4/4 points on a scale by Exacoustos. The tumor in the uterus met the criteria of high probability of malignancy i.e. 8 points on the vascular scale (power Doppler scale ≥ 7 pts.), solid tumor and a size over 8 cm. Blood flow velocity and vascular resistance in the tumor vessels were evaluated (PSV - 5.76 cm/s, ED - 3.16 cm/s, RI - 0.45 S / D - 1.82). Blood flow in the tumor presented low resistance. Hysterectomy without oophorectomy, with an intraoperative histopathological examination, was performed, and a fibroid was confirmed. The tumor was soft, yellow, with small and medium level of dispersed atypia in microscopic examination. There was no necrosis or mitotic figures. The histopathological image confirmed the atypical leiomyoma of low risk of recurrence. Atypical fibroids are rare in gynecological oncology and they do not have the characteristic clinical course. Furthermore, they do not show the typical characteristics during imaging studies, including ultrasound screening, Sometimes, due to the sonographic image, they should be differentiated from sarcomas. Also, it is necessary to exclude malignancy because of their ambiguous histological characteristics.