Endometriosis with an aberrant immunophenotype: Challenging differential diagnosis of glandular lesions in the pelvic lymph nodes.

Case Report: We describe an unusual case of pelvic lymph node endometriosis with an aberrant immunophenotype mimicking metastasis of adenocarcinoma. A 37-year-old patient with a history of invasive cervical adenocarcinoma stage pT1a2 is presented. Due to insufficient loop electrosurgical excision procedure (LEEP) conization, total laparoscopic hysterectomy with pelvic lymphadenectomy was indicated. Intraoperatively, the diagnosis of deep infiltrating endometriosis of parametrial ligament and vesicouterine pouch, endometrioma of the left ovary and Allen Master's syndrome was suspected; the patient had no history or clinical symptoms of endometriosis. A PubMed search of similar cases was followed by a comparison to this case and discussion of the differential diagnosis of glandular lesions in the pelvic lymph nodes is reported.

Results: Histological investigation showed no residual neoplasia; the diagnosis of endometriosis was confirmed. An interesting microscopic finding was represented by a solitary glandular lesion in one pelvic lymph node. Using immunohistochemistry, it was demonstrated that there was a complete loss of oestrogen and progesterone receptor expression (unlike parametrial ligament endometriosis). The diagnosis of endometriosis was based on the presence of endometrial stroma; malignancy was excluded by bland cytomorphologic features and results of immunohistochemical examination.

Conclusions: This type of aberrant of the endometriotic gland immunophenotype has never been presented in the scientific literature before. This finding plays a significant role from the pathology standpoint and, perhaps more importantly, from the clinical standpoint. An asymptomatic patient with a correct diagnosis of lymph node endometriosis did not undergo excessive treatment for false positive diagnosis of metastatic cervical adenocarcinoma.