MR Imaging of an Intramural Adenosarcoma with Pathologic Correlation.

Introduction

Adenosarcomas are rare tumors with low-malignant potential; they are characterized by a mixture of benign glandular epithelial and malignant mesenchymal elements. Adenosarcomas usually occur as endometrial lesions. Intramural adenosarcomas have been rarely reported, and they are commonly found in foci of adenomyosis or in a mural adenomyoma without the involvement of eutopic endometrium.[1] Herein, we demonstrate a case of intramural adenosarcoma with pathologic correlation.

Case Report

The patient was a 58-year-old woman (Gravidity [G]0 Parity [P]0) diagnosed with uterine fibroid and adenomyosis, and she was treated with uterine artery embolization (UAE) 10 years previously. After her treatment, she had been treated with a gonadotropin-releasing hormone agonist. Recently, growth of intramyometrial mass was suspected on vaginal ultrasonography (US). Magnetic resonance imaging was performed for further examination. Magnetic resonance images demonstrated an intramyometrial mass in the anterior wall of the uterine body. The mass showed slightly low intensity on T1-weighted images (WI) and clearly defined inhomogeneous high intensity on T2WI (Fig. 1). The mass showed inhomogeneous contrast enhancement with cystic changes of variable sizes, mild high intensity on diffusion-weighted (DW) images and high intensity (1.71 × 10−4 mm2/s) on apparent diffusion coefficient (ADC) maps. In addition, the margins of the mass showed low-intensity rim on T2WI (Fig. 1). In contrast, the myometrium adjacent to the mass showed low intensity with unclear margins suggesting adenomyosis (Fig. 1). We considered that the mass was endometrial stromal sarcoma arising from adenomyosis. On pathological examination, benign glandular epithelial components surrounded by atypical stromal cells with mitosis (2–3/10HPF) were identified. Sarcomatous overgrowth was absent. The tumor was diagnosed as adenosarcoma. The marginal area showed an increase in collagen fibers accompanied by hypertrophic smooth muscle cells (Fig. 2). Adenomyosis was found in the myometrium which included the area adjacent to the mass. Therefore, the mass was diagnosed as adenosarcoma arising from adenomyosis.

Fig. 1.

Sagittal T2-weighted image (WI). An intramyometrial mass in the anterior wall of the uterine body shows inhomogeneous high intensity. The margin of the mass shows low-intensity rim (arrow). In contrast, the myometrium adjacent to the mass shows low intensity with unclear margin, suggesting adenomyosis. Intracavitary polypoid adenomyoma is also seen (arrow head).

Fig. 2.

Histopathological specimen, Masson trichrome stain (high-power field). The marginal area shows increased collagen fibers with hypertrophic smooth muscle cells.

Discussion

Adenosarcomas show iso or high-signal intensity compared to the myometrium on T1 and T2WI. Small cystic areas are usually observed, which reflect glandular cavities on T2WI. The lesions show strong contrast enhancement similar to that of the myometrium and do not show strong signal intensities on DW imaging.[2] In the present case, the intramyometrial mass showed features consistent with what was previously reported. Moreover, the mass was adjacent to the low-intensity area on T2WI thus reflecting adenomyosis, which is consistent with the previously reported MR imaging findings on a subserosal adenosarcoma.[1]

However, we suspected that the lesion was a low-grade endometrial stromal sarcoma, because the marginal area showed low-intensity rim on T2WI.[3] Low-intensity rim consisting of fibrous tissue layers and/or a decrease in free water caused by the distortion of myometrial tissue following tumor expansion, are reported in endometrial stromal sarcoma cases.[3] In the present case, the marginal area showed hypertrophic myometrium with an increase in collagen fibers. Although we cannot confirm the histologic findings from the previous report, our findings are considered to be consistent with previous findings. We therefore should include adenosarcomas in the differential diagnosis of intramyometrial masses with a low-intensity rim on T2WI.