Is it resistant? A case report of splenic endometriosis and review of the literature

A 31-year-old primigravida female patient presented with swelling and intermittent abdominal pain in the right lower quadrant for two months. She had a history of solid mass excision via cesarean section due to 22x15 cm mucinous cystadenoma in her right ovary. On physical examination, the right lower quadrant was tender, and a palpable mass was found in the right lower quadrant at the upper part of the Pfannenstiel incision. Ultrasonography was planned for further evaluation, and preoperative ultrasonography demonstrated a hypoechoic lesion 22x38 mm in size at the level of right rectus muscle and a cystic mass of 90x85 mm in size in the superior pole of spleen. An magnetic resonance imaging was performed and revealed 93x85 mm cystic lesion with septae in the superior pole of spleen and a heterogenic mass on the medial side of right rectus muscle ( Fig. 1 ). Due to suspicion of hydatic cyst disease, serologic examination was performed and resulted as negative. In accordance with physical examination and radiological assessment, surgery was indicated due to huge splenic cyst and abdominal wall lesion. Laparoscopic splenectomy and mass excision from the anterior abdominal wall were performed. The patient was discharged without complications on the third postoperative day. Pathology was reported as endometriosis for the mass from the anterior abdominal wall. Macroscopic examination of the spleen revealed 110x100x98 mm cystic mass at the superior pole of spleen. Inner surface of the cyst was yellow-tan colored with smooth texture. Microscopic examination showed that cyst had no epithelial lining and there were two foci of endometriosis between the hyalinized wall layers near the splenic parenchyma ( Fig. 2 ). Immunohistochemical study showed estrogen and progesterone receptor positivity ( Fig. 2 ). Pathologic diagnosis was reported as “cystic mass with no epithelial lining, foci of endometriosis in the cyst wall”. During the follow-up, there was no problem. Informed consent was obtained from the patient and the Institutional Review Board approved the study (approval no: 2020-01/8). MRI: An 8.44×9.26 cm lesion with sharp borders within the spleen parenchyma which appears hypointense in axial T1 sequence (A) and hyperintense in coronal T2 sequence (B) . T2 sequence revealed minimal border irregularity on the inner side of the cyst. MRI cystographic investigation revealed a cystic lesion in the spleen parenchyme (C) . Post-contrast axial fat suppressed T1 investigation revealed a heterogenous lesion medial to the right rectus muscle (D) . Endometrial glands in the cyst wall near the splenic parenchyma (A) ; same glands with scant stroma in higher magnification (B) . Second focus of endometriosis near the splenic parenchyma, Asterisk denotes the lumen of the cyst (C) (H&E Stain). ER (D) (×100 µm) and PR (E) (×200 µm) positivity in the endometriosis focus.

Although extrapelvic endometriosis was reported in various organs before, spleen was mentioned as refractory for endometriosis. This case, as the fourth in the field since 2020, is valuable and unique by supporting the previous papers on splenic endometriosis and strengthening the existing literature [ 8 – 10 ]. The evaluation of the 3 cases with our case will guide us in assessing clinical presentation of splenic endometriosis and its interpretation. The demographic, clinical and pathological data of the four cases are given in Table 1 . Demographic, clinical and pathological features of the cases NM: Not mentioned. Studies showed that endometriosis has multifactorial nature and there are several factors contributing to susceptibility of individuals such as genetic alterations, immune impairments and environmental factors [ 3 ]. Hypothesis of natural killer cell dysfunction in endometriosis is thought and mentioned to be in the pathophysiology of the disease [ 11 ]. While our patient has no immunological disorder, our report reveals that endometriosis of the spleen may occur in immunocompetent individuals. Earlier in the literature, Samani et al. [ 12 ] reported that migration of endometriosis-derived cells to various organs, including spleen is possible in a murine model. Weyl et al. [ 10 ] reported the first case of splenic endometriosis in a patient with metastatic breast cancer. Coelomic metaplasia and vascular/lymphatic metastasis theories may be more coherent for extrapelvic implantations, including spleen as in this case. As explained in another case report, splenic endometriosis was diagnosed in a patient with history of splenorrhaphy 10 years ago [ 8 ]. Authors postulated the iatrogenic seeding mechanism as the pathophysiology for that case [ 4 ]. Since gynecological intervention history of the patient was non-remarkable, to us, it is not possible to agree with this interpretation. In our case, the mass on the anterior abdominal wall was likely caused by iatrogenic implantation due to previous cesarean section. There is also possibility for the same mechanism of seeding in splenic implantation but other theories such as coelomic metaplasia, vascular and lymphatic metastasis may also be coherent. The last case in the literature reports incidentally found splenic endometriosis in a 26-year-old female patient who had type 1 DM and eosinophilic esophagitis [ 9 ]. After identification of a 10x9x9 cm splenic cyst in cross-sectional imaging, the patient had a laparoscopic splenectomy due to size and proximity to the splenic hilum of the cyst. The main complaints of the patient were bloating and early satiety and these were contributed to her eosinophilic esophagitis. Like our case, after resection of huge splenic cyst, final pathology revealed splenic tissue with an endometriotic cyst as characterized by endometrial glands and stroma unexpectedly. Also, the authors claimed that their patient had no history of endometriosis, had regular menstrual cycles and was nulliparous. In all three cases, also in our report, estrogen and progesterone receptor positivity were used as indicators of endometriosis. As stated in current guidelines, surgical removal is the best option for the treatment of extrapelvic abdominal endometriosis [ 13 , 14 ]. On the other hand, if endometriosis is confirmed with biopsy and the patient has no symptoms due to endometriosis, clinical follow-up with routine ultrasound monitoring is sufficient [ 5 , 14 , 15 ]. Infertility and pain have been the major indications for operation in most cases. In our case, due to the patient’s unidentified abdominal pain for two months and the complex cystic lesion in spleen, resection is done for all lesions possibly culprit. The patient’s complaints disappeared immediately after surgery. Furthermore, intraparenchymal hemorrhage and subsequent spontaneous perforation of the spleen due to presence of endometrial tissue might be an emergent and devastating clinical presentation. In conclusion, the idea of resistance of the spleen against endometriosis became outdated with this case report as the fourth case in the literature. Therefore, splenic endometriosis is getting out of being a rare occasion and can be thought of as a differential diagnosis for lesions of spleen in women with unidentified cyclic abdominal pain.