Primary extrauterine cystic low-grade endometrioid stromal sarcoma mimicking stromal endometriosis. A case report emphasizing the differential diagnosis and its potential local aggressive behavior

277 Short communication Primary extrauterine cy Stic low -grade endometrioid Stromal Sarcoma mimicking Stromal endometrio SiS. a ca Se re Port em Pha Sizing the differential diagno SiS and itS Potential local aggre SSive behavior S imona S tolnicu 1 , c S ilip t unde 1 , G abo S S zilard 1 , c ri S tian p odoleanu 2 , F ranci S c r oz S nyai 3 1 Department of Pathology , University of Medicine, Pharmacy , Sciences and T echnology of T argu Mureș, Romania 2 Department of Internal Medicine IV , University of Medicine, Pharmacy , Sciences and T echnology of T argu Mureș, Romania 3 Department of Gynecology and Obstetrics, University of Medicine, Pharmacy , Sciences and T echnology of T argu Mureș, Romania Genital and pelvic endometriosis is a frequently encountered lesion and its impor - tance rely on associated symptoms and its propensity for malignant transforma- tion. In the present paper we comment on the importance of correctly diagnose the malignant transformation of an endometriotic lesion into a cystic low-grade endometrial stromal sarcoma, which is a very rare event. Moreover, we discuss the ability of a low-grade endometrial stromal sarcoma to locally recurr and the differ - ential diagnosis with stromal endometriosis, a lesion that is very rare, almost always microscopic and solid. Key words: stromal endometriosis, cystic endometrial stromal sarcoma, malignant transformation. doi: httpS :// doi . orG /10.5114/ pjp .2020.99795 p ol j p athol 2020; 71 (3): 277-280 A 38-year-old patient, 8 gravida and 4 para, with morbid obesity and no relevant clinical history , pre- sented with acute abdominal symptoms. Explorato- ry laparotomy identified a cystic lesion adjacent to the right ovary and fallopian tube, attached to the rec- tum, which was surgically removed. The 40 mm di- ameter unilocular cyst, with a smooth 5 mm thick wall and hemorrhagic content, was partially lined with unistratified endometrioid type of epithelium and presented multiple nodules of endometrioid type of stromal cells within the cystic wall and involv- ing vascular spaces, positive for CD10, ER, PR and lacking atypia. Based on the cystic appearance and the dominance of stromal type of cells with benign features, the lesion was misinterpreted as cystic stro- mal endometriosis (Fig. 1). Hormonal therapy (Zola- dex) for a period of 3 months was indicated but after one dose the patient declined further therapy . T en months later she presented with pelvic pain. Intraoperative examination revealed a 70 mm diam- eter solid tumor mass attached to the rectum and associated with a second 30 mm diameter solid nod- ule, involving the right ovary while the uterus was unremarkable. Microscopically , both solid nodules presented a diffuse proliferation of small, uniform tu- mor cells, resembling endometrial stromal cells, with round to ovoid nuclei, finely granular chromatin, poorly defined cell borders, low mitotic activity , pos- itive for ER, PR and CD10. There was a proliferation of small vessels and arterioles present throughout the tumor stroma, while vascular invasion as well as irregular tongues of tumor cells invading the stroma 278 Simona Stolnicu , cSilip t unde , GaboS Szilard, et al . Fig. 1. Low-grade endometrioid stromal sarcoma: the first lesion was misinterpreted as cystic stromal endometriosis due to the cystic appearance, partially lined by unistratified endometrioid type of epithelium (A) although presenting multiple nodules of endometrioid type of stromal cells within the cystic wall (B, C) and involving vascular spaces where it presented an angiomatous pattern (D); the tumor cells were positive for PR (E, F) and CD10 (G, H) A B C D E F G H 279 CystiC low -grade endometrioid stromal sarComa mimiCking stromal endometriosis Fig. 2. Recurrence of a low-grade endometrioid stromal sarcoma: ultrasound examination revealed a lesion with unusual peripheral vascularization (A) and solid (B) located adjacent to the rectum; multiple coalescent tan to yellow soft nodules involving the ovary (C) and attached to the rectum (D) were solid in appearance; microscopically , both solid nodules presented a diffuse proliferation of small, uniform tumor cells, resembling endometrial stromal cells (E), with minimal nuclear atypia and mitotic activity (F); the tumor cells were positive for PR (G) and CD10 (H) A B C D E F G H 280 Simona Stolnicu , cSilip t unde , GaboS Szilard, et al . were only present in the nodule adjacent to the rec- tum (Fig. 2). The final diagnosis was of recurrent low-grade endometrioid stromal sarcoma involving the rectum and ovary . The surgical treatment was followed by radiotherapy and hormone therapy . Endometriosis is a benign lesion characterized by the presence of endometrial tissue outside the endo- metrium and myometrium. Most frequently , endome- triosis affects patients in their reproductive age, and involves organs of the female genital tract and pelvis, but involvement of the intestinal tract or remote or - gans is also frequently encountered. Depending on their duration and location in relation to the perito- neal surface, endometriotic foci may appear as punc- tate, spots, or patches, and may form nodules or cysts of various colors. Endometriotic cysts most commonly involve the ovaries or paraovarian tissue, rarely ex - ceed 15 cm in diameter, are commonly covered with dense, fibrous adhesions, which may result in fixation to adjacent structures, and have a semifluid, chocolate- colored content material. Usually both endometrial epithelium and stroma are seen, but cases in which only one component is present can occur. Cases of endome- triosis characterized by absence or paucity of glands, so-called stromal (or micronodular) endometriosis, are most commonly encountered in the superficial ovari- an cortex, in the form of one or multiple small nod- ules of endometriotic stroma. Stromal endometriosis does not usually progress into cysts and it is clinically irrelevant. Malignant transformation of ectopic endometrio- sis is infrequent, occurring in up to 1% of all wom- en with endometriosis [1]. Most cases of malignant transformation occur in the ovary and are of epithe- lial type, represented by endometrioid and clear cell carcinoma, while mesenchymal tumors are very un- common, representing less than 1% of all cases [1, 2, 3, 4]. Among mesenchymal malignant lesions, low-grade endometrioid stromal sarcoma can occur in the form of a solid, soft tan to yellow nodule. V ery rare, low-grade endometrioid stromal sarcomas can develop as a cystic lesion or may contain benign-ap- pearing or atypical endometrial glands, to the extent that confusion with endometriosis may occur. In the present case, the first lesion was a cystic low-grade stromal sarcoma, misinterpreted as benign stromal endometriosis based on the cystic appear - ance and the presence of endometrioid type of epi- thelium despite the infiltrative pattern in association with vascular invasion. Pathologists should be aware of the fact that stromal endometriosis is very rare, almost never cystic, and should extensively sample lesions of this type to avoid misinterpretation. The authors declare no conflict of interest. References 1. Heaps JM, Nieberg RK, Berek JS. Malignant neoplasms aris- ing in endometriosis. Obstet Gynecol 1990; 75: 1023-1028. 2. Mostoufizadeh M, Scully RE. Malignant tumors arising in en- dometriosis. Clin Obstet Gynecol 1980; 23: 951-963. 3. Scully RE, Richardson GS, Barlow JF . The development of ma- lignancy in endometriosis. Clin Obstet Gynecol 1966; 9: 384- 411. 4. Y antiss RK, Clement PB, Y oung RH. Neoplastic and pre-neo- plastic changes in gastrointestinal endometriosis: a study of 17 cases. Am J Surg Pathol 2000; 24: 513-524. Address for correspondence Simona Stolnicu Department of Pathology University of Medicine, Pharmacy , Science and T echnology of T argu Mureş 38 Gheorghe Marinescu Street T argu Mureş 540139, Romania tel. +40 265 215 551 e-mail: [email protected]