Endometrial stromal sarcomas with extensive endometrioid glandular differentiation: report of a series with emphasis on the potential for misdiagnosis and discussion of the differential diagnosis

Aims:  To describe a series of endometrial stromal sarcomas with large numbers of endometrioid‐type glands. Methods and results:  The eight tumours occurred in patients aged 42–74 years. In three cases, the neoplasm arose in the uterine corpus and in the others there was either an extrauterine origin or the origin could not be determined since multiple sites were involved. In four cases, glands were present throughout the neoplasm and in the others there were areas of typical endometrial stromal sarcoma without glands. In one case, glands were present only in the recurrent neoplasm. The malignant stromal component comprised, for the most part, typical endometrial stromal sarcoma. In two patients, repeated biopsy specimens from the vagina or cervix were initially diagnosed as endometriosis, and in some cases there was a significant delay in diagnosis. Apart from endometriosis, other diagnostic considerations, depending on the tumour location and exact morphology, included adenomyosis, adenosarcoma and carcinosarcoma. Conclusions:  Endometrial stromal sarcoma with extensive endometrioid glandular differentiation is rare. The presence of glands often results in diagnostic difficulty with a significant risk of misdiagnosis or delay in diagnosis. It is likely that some cases reported in the literature as aggressive endometriosis represent this entity.