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Year : 2021  |  Volume : 64  |  Issue : 1  |  Page : 171-173
Collision tumor of the ovary: Fibroma and mature cystic teratoma

1 Department of Pathology, Universiti Kebangsaan Malaysia Medical Center; Department of Pathology, Prince Court Medical Centre, Kuala Lumpur, Malaysia
2 Department of Pathology, Universiti Kebangsaan Malaysia Medical Center, Kuala Lumpur, Malaysia
3 Department of Pathology, Prince Court Medical Centre, Kuala Lumpur, Malaysia
4 Department of Obstetrics and Gynaecology, Prince Court Medical Centre, Kuala Lumpur, Malaysia

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Date of Submission28-Aug-2019
Date of Decision22-Oct-2019
Date of Acceptance05-Dec-2019
Date of Web Publication8-Jan-2021


Collision tumor consists of two tumors occurring in the same organ without intermixture of the two cell types. The most common type of collision tumor in ovary is between teratoma and surface epithelial tumor. A 38-year-old woman presented with complained of lower abdominal pain and tightness, and a solid partially cystic left ovarian mass with minimal ascites was detected. Left salpingo-oophorectomy was performed. The ovarian mass measured 15 × 12 × 7 cm with a pedunculated mass on its surface which measured 6 × 2.5 × 2.5 cm. Histologically, it was a collision tumor of fibroma and mature cystic teratoma. Fibroma becomes more edematous as their size increases, which is frequently accompanied by the escape of increasing quantities of fluid from the tumor surfaces. Ascites is often detected when the fibroma is more than a diameter of 10 cm. It is important to identify the different components of a collision tumor for proper management.

Keywords: Collision tumor, fibroma, germ cell tumor, ovary, teratoma

How to cite this article:
Tan GC, Chandramaya SF, Noordin A, S. Tay PY. Collision tumor of the ovary: Fibroma and mature cystic teratoma. Indian J Pathol Microbiol 2021;64:171-3

How to cite this URL:
Tan GC, Chandramaya SF, Noordin A, S. Tay PY. Collision tumor of the ovary: Fibroma and mature cystic teratoma. Indian J Pathol Microbiol [serial online] 2021 [cited 2023 Mar 29];64:171-3. Available from:

   Introduction Top

Mature cystic teratoma of the ovary is the commonest germ cells tumor and accounts for 27%–44% of all ovarian tumors.[1] On rare occasion, collision tumor may occur, which consists of two histologically distinct tumors, in the same organ without intermixture of the 2 cell types. Of these, the most common is a teratoma with surface epithelial neoplasm.[2] There are only a handful of reported cases of ovarian teratoma with fibromatous tumors.[3],[4] Here, we report a case of benign fibroma with mature cystic teratoma of ovary with minimal ascites in a 38-year-old woman.

   Case Presentation Top

A 38-year-old patient presented to our hospital with complained of lower abdominal pain and tightness. She also had pollakiuria and backache. Her period was very irregular of 2 to 3 times per year. Preoperative ultrasound showed a large pelvic mass of 15.0 × 10.0 cm. Her hematological investigation was normal (hemoglobin: 13.6 g/dl; white cell count: 13.7 × 103/μl; and platelet count: 333 × 103/μl). Laparotomy and left salpingo-oophorectomy and omentectomy were performed.

Intraoperatively, a solid partially cystic left ovarian mass with irregular surface was identified. The uterus appeared small and the right ovary appeared normal. There was small amount of ascites. There was no seedling in the omentum and peritoneal surface. However, a clinical suspicion of malignancy was raised due to the presence of a solid cystic ovarian mass with ascites. Omentectomy was also removed as a precaution. Postoperative recovery was uneventful. She was discharged on the third day after surgery and remained well at 3 weeks follow-up.

Pathological examination

On gross examination, the left ovarian mass was firm, grayish brown, weighed 1.2 kg and measured 15.0 × 12.0 × 7.0 cm. A pedunculated mass arises from the main mass which measured 6.0 × 2.5 × 2.5 cm [Figure 1]a. Cut section of the main mass showed predominantly solid with minimal cystic area at the subcapsular region, while the pedunculated mass showed multiple cysts that contained sebaceous and gelatinous materials. Microscopically, the main ovarian mass showed cellular neoplastic spindle cells arranged in storiform pattern, accompanied by collagen deposition and edematous areas [Figure 1]b and c]. Mitotic figures are inconspicuous. Immunohistochemically, the neoplastic spindle cells have low Ki-67 proliferative index (<1%) [Figure 1]d. In contrast, the pedunculated mass show fibrous cyst wall partially lined by keratinizing stratified squamous epithelium and contains hair follicles, glial and adipose tissues [Figure 1]e and [Figure 1]f.
Figure 1: A pedunculated mass (arrow) arises from the main ovarian mass (a). The main mass composed of neoplastic spindle cells that are arranged in storiform pattern and displaying uniform nuclei (b-20×; c-40×). The Ki-67 proliferative index is low (d-40×, yellow arrow indicates positive staining) (Inset: Positive control using tonsil tissue). The pedunculated mass composed of fibroconnective tissue covered by keratinizing stratified squamous epithelium with underlying adipose tissue (e) and glial tissue (f)

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   Discussion Top

Most collision tumors are diagnosed postoperatively. Recently, a study shown that it may be possible to identify collision tumor by CT/MRI imaging.[5] Mature cystic teratoma is one of the most common components in a collision tumor.[2] Various combinations have been reported such as teratoma and cystadenocarcinoma, teratoma and mucinous cystadenoma, teratoma and serous cystadenocarcinoma, teratoma and carcinosarcoma, choriocarcinoma and cystadenoma, sarcoma and mucinous tumor, sarcoma and serous carcinoma, serous cystadenoma and Sertoli-Leydig cell tumor, granulosa cell tumor and ovarian hepatoid carcinoma, and granulosa cell tumor and endometroid carcinoma.[2],[6],[7]

Fibroma and teratoma are uncommon.[3],[4] Fibroma is one of the sex cord-stromal tumors, constituting for approximately 4% of all ovarian neoplasms. These tumors become more edematous as their size increases, which is frequently accompanied by the escape of increasing quantities of fluid from the tumor surfaces. Ascites is detected in association with 10% to 15% of ovarian fibromas exceeding a diameter of 10 cm.[8] Our patient had an ovarian tumor of 15 cm in diameter accompanied by small amount of ascites.

Fibromatous tumors can be divided into fibroma, cellular fibroma, and fibrosarcoma. Cellular fibroma has increased cellular density and brisk mitotic activity and is considered to be tumors of low malignant potential, particularly if ruptured or associated with adhesions,[9] whereas fibrosarcomas are highly malignant neoplasms, distinguished by their greater cellular density and moderate to marked pleomorphism.[9] Irving and colleagues (2006) studied 75 cases of cellular fibromas of the ovary and suggested the term “mitotically active cellular fibroma” for neoplasm with bland cytology with ≥4 mitosis/10 HPF.[10]

Fibromas are predominantly solid. Cystic areas if present are usually small and are without multiloculation. Some fibromas undergo prominent cystic degeneration and may be mistaken as surface epithelial tumors. However, cyst secondary to degeneration does not have an epithelial lining.[11] The ovarian mass in our patient has cystic area at the subcapsular region and microscopically, it is devoid of epithelial lining, suggests that it is likely due to degenerative change. Interestingly, a case of well-differentiated ovarian fibrosarcoma has been described, with low-grade cytological atypia and 1-2 mitosis/10 HPF developing liver metastasis one year later.[12] The authors suggested that high rates (<10%) for Ki-67 could contribute to the diagnosis of malignancy, despite having a low mitotic rate. On the contrary, Huang et al. (2010)[13] study showed that Ki-67 was not a significant independent prognostic factor for survival.

Fibrosarcoma can arise de novo or from preexisting benign fibromatous tumors.[14] It is commonly encountered in menopausal or postmenopausal woman with a mean age of 49 years.[12] Kim reported a case of torsion of collision tumor in a postmenopausal woman.[15] The overall feature of the ovarian mass in our case is benign: relatively young age, no necrosis, no cytological atypia, low mitotic activity, and low Ki-67 proliferative index (<1%). However, the solid cystic nature of tumor with the presence of ascites might lead to possibility of being mistaken as malignant tumor. In conclusion, collision tumor of the ovary is a rare entity that clinicians, radiologists, and pathologists should be aware to prevent misdiagnosis. Thorough sampling of the tumor is recommended in a solid cystic ovarian tumor with ascites to prevent sampling error. It is important to correctly identify the component of the tumor for proper management.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Tavassoeli FA, Devilee P. Pathology and Genetics Tumours of the Breast and Female Genital Organs. IARC WHO Classification of Tumours. Vol. 4, 3rd ed. 2003.  Back to cited text no. 1
Singh AK, Singh M. Collision tumours of ovary: A very rare case series. J Clin Diagn Res 2014;8:FD14-6.  Back to cited text no. 2
Kruger S, Schmidt H, Kupker W, Rath FW, Feller AC. Fibrosarcoma associated with a benign cystic teratoma of the ovary. Gynecol Oncol 2002;84:150-4.  Back to cited text no. 3
Stamp GW, McConnell E. Malignancy arising in cystic ovarian teratomas: A report of 24 cases. Br J Obstet Gynaecol 1983;90:671-5.  Back to cited text no. 4
Peng Y, Lin J, Guan J, Chen L, Zhang X, Li S, et al. Ovarian collision tumors: Imaging findings, pathological characteristics, diagnosis, and differential diagnosis. Abdom Radiol (NY) 2018;43:2156-68.  Back to cited text no. 5
Karki D, Karki S, Adhikari P, Dahal M, Adhikari M, Adhikari B. Collision tumor of ovary: A rare entity. Asian J Med Sci 2018;9:61-4.  Back to cited text no. 6
Rahar S, Khetarpal S. Collision tumor of ovary: Serous adenocarcinoma and mature cystic teratoma. Int J Med Lab Res 2019;4:45-9.  Back to cited text no. 7
Samanth KK, Black WC. Benign ovarian stromal tumors associated with free peritoneal fluid. Am J Obstet Gynecol 1970;107:538-45.  Back to cited text no. 8
Prat J, Scully RE. Cellular fibromas and fibrosarcomas of the ovary: A comparative clinicopathologic analysis of seventeen cases. Cancer 1981;47:2663-70.  Back to cited text no. 9
Irving JA, Alkushi A, Young RH, Clement PB. Cellular fibromas of the ovary: A study of 75 cases including 40 mitotically active tumors emphasizing their distinction from fibrosarcoma. Am J Surg Pathol 2006;30:929-38.  Back to cited text no. 10
Young RH. Sex cord-stromal, steroid cell, and other ovarian tumors with endocrine, paraendocrine, and paraneoplastic manifestations. In: Kurman R, Ellenson LH, Ronnett BM, editors. Blaustein's Pathology of the Female Tract. 6th ed. New York, NY, USA: Springer; 2011. p. 785-846.  Back to cited text no. 11
Garcia Jimenez A, Castellvi J, Perez Benavente A, de Corcuera Frutos ID, Cajal SR. Ovarian fibrosarcoma: Clinicopathologic considerations about the intraoperative and post-surgical procedures. Case Rep Med 2009;2009:4. Article ID 802817.  Back to cited text no. 12
Huang L, Liao LM, Wang HY, Zheng M. Clinicopathologic characteristics and prognostic factors of ovarian fibrosarcoma: The results of a multi-center retrospective study. BMC Cancer 2010;10:585.  Back to cited text no. 13
Talerman A. Non-specific tumors of the ovary, including mesenchymal tumors and malignant lymphoma. In: Kurman RJ, editor. Blaustein's Pathology of the Female Genital Tract. 4th ed. New York, NY: Springer Verlag; 1993. p. 916-7.  Back to cited text no. 14
Kim JH. Torsion of collision tumor: Dermoid cyst and fibrothecoma with postmenopausal bleeding. J Menopausal Med 2016;22:114-7.  Back to cited text no. 15

Correspondence Address:
Geok C Tan
Department of Pathology, Universiti Kebangsaan Malaysia Medical Center, Jalan Yaacob Latif, Bandar Tun Razak, Cheras - 56000, Kuala Lumpur
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJPM.IJPM_670_19

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