Extraovarian Fibroma with Minor Sex Cord Elements-a Rare Tumour at Rare Site.

Sex cord stromal tumour (SCST) of ovary account for 5–8% of all ovarian malignancies. These include fibroma, thecoma, fibro-thecoma, Leydig cell tumour, granulosa cell tumour, and Sertoli cell tumour. Although considered primary ovarian malignancy, SCST has been described in extraovarian location also. Extraovarian SCST is a rare occurrence, and so far, only 25 cases have been reported in literature and only one amongst them was extraovarian fibroma with minor sex cord element. Considering the rarity, diagnosis and proper treatment remain the real challenge in these tumours. To the best of our knowledge, this is the second case of extraovarian fibroma with minor sex cord element to be reported. Herein, we report a case of 41-year-old lady who presented with large abdomino-pelvic mass which was considered ovarian tumour; however, intraoperatively both ovaries and uterus were found to be normal, and the mass was actually arising from sigmoid mesocolon.

Extraovarian, Sex cord stromal tumour, Minor sex cord element

Sex cord stromal tumour (SCST) of ovary account for 5–8% of all ovarian malignancies. These include fibroma, thecoma, fibro-thecoma, Leydig cell tumour, granulosa cell tumour, and Sertoli cell tumour. Although considered primary ovarian malignancy, SCST has been reported in extraovarian location also. The commonly reported extraovarian locations are broad ligament, retroperitoneum, mesentery, fallopian tube, adrenal gland, and omentum [1]. The commonly reported histological types are granulosa cell tumour followed by fibro-thecoma and thecoma [2]. Extraovarian SCST is a rare occurrence and so far only 25 cases have been reported in literature and only one amongst them was extraovarian fibroma with minor sex cord element. It may pose a diagnostic challenge radiologically and histologically. To the best of our knowledge, this is the 2nd case of extraovarian fibroma with minor sex cord elements to be reported. Case Summary A 41-year-old premenopausal lady with previous history of two LSCS, was evaluated for gradual abdominal distension over 2 months. On clinical examination, a large abdominopelvic mass was felt reaching till epigastric region. Contrast-enhanced computerised tomography (CECT) scan of the abdomen and pelvis was suggestive of a large, well-encapsulated heterogenous mass arising from the pelvis and left iliac region, with hyperdense nodular areas and few irregular hypodense cystic/necrotic regions, left ovary was not seen separately from the lesion (Fig. 1). CECT Chest was normal. Tumour marker CA-125 was 51.5U/ml (normal limit < 35U/ml), CEA, CA-19–9 levels were normal. Colonoscopy was suggestive of submucosal bulge in sigmoid colon without mucosal involvement. Considering the ovarian tumour, patient was planned for staging laparotomy with total abdominal hysterectomy + bilateral salpingo-oophorectomy with omentectomy. Intraoperatively, mass was arising from sigmoid mesocolon with the sigmoid colon splaying over it, clinically and radiologically mimicking gastrointestinal stromal tumour (GIST). The omentum was densely adherent to the mass and mild ascites were present. Both the ovaries, fallopian tubes, and uterus were normal (Fig. 1). Hence, she underwent en-bloc excision of the mass with omentum and segmental resection-anastomosis of sigmoid colon, sparing uterus and ovaries. Intraoperative course and post-operative recovery were smooth and uneventful. Patient was discharged on full diet on post-operative day 8. Peritoneal fluid for cytology was negative for malignancy. Gross pathological examination revealed encapsulated nodular mass of size 27 × 20 × 9 cm. Microscopic examination was suggestive of spindle cell tumour; tumour composed of fascicles of fusiform spindle cells possessing eosinophilic cytoplasm and slender elongated oval vesicular nuclei. One of the sections also showed features of ovarian stroma with sex cord-like structures. Omentum was grossly unremarkable. Immunohistochemical markers were positive for SF1, PR, calretinin, Inhibin, and ER (Fig. 2). Reticulin stain showed reticulin fibres wrapping around individual tumour cells. Tumour cells were immune-negative for SMA, desmin, S-100, CD 34, DOG-1, C-kit, H-caldesmon, cytokeratin, EMA, MDM2, CD21, CD23, and CD 35. This confirmed the diagnosis of fibroma with minor sex cord elements. Since the diagnosis was confirmed retrospectively on final histology and immunochemistry, option of completion surgery, i.e. total hysterectomy and salpingo-oophorectomy, was discussed with patient in detail. However patient chose close surveillance. She was kept on observation and at 2 years follow-up, patient is doing well without any evidence of recurrence. Follow-up ultrasound scan was suggestive of normal endometrium and bilateral adnexa.

According to the World Health Organisation (WHO), primary ovarian malignancies are classified into epithelial tumours, mesenchymal tumours, mixed epithelial and mesenchymal tumours, sex cord stromal tumours, germ cell tumours, and miscellaneous tumours [3]. Sex cord stromal tumours (SCSTs) of the ovary are uncommon nonepithelial tumours, accounting for approximately 5 to 8% of all ovarian malignancies [4]. Ovarian sex cord stromal tumours are composed of sex cord cells (granulosa cells or Sertoli cells) and cells of stromal or mesenchymal type (fibroblasts or theca cells or Leydig cells). Usually sex cord element either forms a major component of the tumour or is absent (as in pure stromal tumours). Young and Scully introduced the terminology of ovarian stromal tumours with minor sex cord element in 1983, when minor sex cord elements occupy less than 10% of the area of tumour on any slide [5]. Extraovarian site represents a rare location for sex cord stromal tumour. Till date, only 25 cases of extraovarian sex cord stromal tumour have been reported, out of which only one was reported to be extraovarian fibroma with minor sex cord element. To the best of our knowledge, our case represents the second case of extraovarian fibroma with minor sex cord element to be reported. The occurrence of SCST at extraovarian site can be explained histogenetically by the development of sex cord cells and their derivatives from coelomic epithelium rather than from stroma of the ovary, through which the primordial germ cells migrate during embryonic life [6]. The other explanations to the occurrence of extra-gonadal SCST are ectopic gonadal stromal tissue and supernumerary ovaries [7]. Extraovarian SCST occurs more frequently in patients ranging from 22 to 78 years of age [2]. The most common presentation of extraovarian SCST is intra-abdominal mass, however, they can present with functional symptoms due to hormonal excess. Functional symptoms can be due to hyper estrogenic state (granulosa or theca cells) like menorrhagia or hyperandrogenic state (Sertoli cells or Leydig cells) like hirsutism, acne, deepening of voice, clitoral hypertrophy, and amenorrhoea [8]. The common locations for extraovarian SCST are broad ligament, retroperitoneum, mesentery, fallopian tube, adrenal gland, and omentum (1). All the histologic variants of ovarian SCST are reported at extraovarian sites; however, granulosa cell tumour followed by fibro-thecoma and thecoma are more commonly encountered at extraovarian location (2). Fibromas usually appear homogenous solid masses on imaging since they contain fibrous and collagenous contents. However, our case had unusual imaging finding of heterogenous appearance with solid and cystic areas adding to the diagnostic dilemma. The characteristic histologic features of fibroma are storiform and fascicular spindle proliferation with variable cellularity and background collagen deposition. The diagnosis of sex cord stromal tumour is supported by immunohistochemical examination. Fibroma stain positive for calretinin, splicing factor-1 (SF-1); weak to moderate staining for Wilms tumour- 1(WT-1). They show variable Inhibin positivity and are negative for CD-10. While the role of intra-operative frozen section diagnosis is well established for management of epithelial ovarian tumours, its use in SCST has major limitations (4). When intra-operative frozen section is indeterminate, the potential need for further completion surgery should be discussed with patients who opt for conservative surgery, if final diagnosis of malignant neoplasm is established. The staging system for all primary ovarian cancers is the same regardless of histology (SCST, epithelial cell, germ cell). By and large, SCST are generally considered benign and are associated with favourable prognosis. However, the clinical behaviour and prognosis of these rare tumours are not clearly defined. While conservative surgery (oophorectomy/ovarian cystectomy) is adequate for benign SCST, management of malignant SCST is more aggressive [8]. Given the rarity of extraovarian SCST, there are no standardised treatment protocols. While current guidelines recommend comprehensive surgical staging for the management of any ovarian malignancy, fertility-sparing surgery can be considered for patients with apparent early-stage disease and/or low-risk tumours who wish to preserve fertility. NCCN guidelines recommend consideration of total hysterectomy with bilateral salpingo-oophorectomy after childbearing is completed [9]. The lymph nodal involvement is uncommon in SCST, hence routine lymphadenectomy is not warranted [10].

Extraovarian fibroma with minor sex cord element is a rare entity, and precise pre-operative diagnosis is challenging. Currently, extraovarian SCST is treated like ovarian SCST only. While fertility-preserving surgery can be considered in benign SCST, long-term follow-up is required. Abbreviations - SCST Sex cord stromal tumour - CECT Contrast enhanced computerised tomography - GIST Gastro intestinal stromal tumour - WHO World Health Organisation - HnE Haematoxylin and eosin Author Contribution Monika Pohekar: data acquisition, primary manuscript drafting. Sabireen: manuscript review and editing. Sandip Bipte: revising the manuscript critically. Rajesh S. Shinde: conception and design, finalisation of manuscript. Data Availability Data is available with author and appropriate consent was obtained from patient. Declarations Conflict of Interest The authors declare no competing interests. Footnotes Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Highlights 1. Extraovarian fibroma with minor sex cord elements is a rare entity and management guidelines are not clearly defined. 2. The pre-operative diagnosis by clinico-radiological findings is difficult to establish and hence poses a diagnostic dilemma. 3. The follow-up of patients opting for fertility-preserving surgery is crucial as the chances of developing endometrial carcinoma are high. The option of completion of surgery was discussed with our patient, and she chose close surveillance. The patient is doing well at 2-year follow-up.

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