Adenomyosis with sparse glands. A potential mimic of low-grade endometrial stromal sarcoma.

Most cases of adenomyosis are easily recognized by the presence of intramyometrial aggregates of endometrial glands and endometrial stromal cells surrounded by hypertrophic smooth muscle. The authors report seven cases of adenomyosis with sparse glands, which was a finding that initially caused difficulties in diagnosis and raised the question of low-grade endometrial stromal sarcoma (LGESS). The patients' ages ranged from 51 to 81 years. All were postmenopausal. Each had undergone hysterectomy for a variety of reasons unrelated to the adenomyosis. Microscopic examination of the uteri disclosed multiple intramural nests of adenomyotic endometrial stromal cells without endometrial glands, ranging from 0.5 mm to 8.0 mm in maximum dimension. The percentage of adenomyotic foci without glands in each case ranged from 40% to 94%. Two cases also had foci of intravascular intrusion by the gland-poor adenomyotic stroma. The most useful features for differentiating adenomyosis with sparse glands from LGESS include: (1) its occurrence as an incidental finding in uteri removed for other reasons; (2) the microscopic size of the adenomyotic foci without grossly evident tumor nodules; (3) a distinctive concentric zonal organization of the gland-poor stromal aggregates, with less cellular pale centers surrounded by a thin rim of stromal or smooth muscle cells with increased cellularity, often with a thicker, but less well-defined, peripheral zone of hypertrophic myometrial smooth muscle; (4) the atrophic appearance of the stromal cells and absence of nuclear atypia and mitotic figures; (5) an absence of sclerotic areas, foam cells, sex cordlike structures, hemangiopericytoma-like vascular pattern, prominent vascular invasion and extrauterine extension commonly found in LGESS; (6) the presence of typical adenomyosis with glands elsewhere in the myometrium; and (7) the postmenopausal age of the patient.