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Introduction

Mature cystic teratomas are benign unilateral tumors often diagnosed in young females. Teratomas are composed of tissues derived from the three germ layers; ectoderm, mesoderm and endoderm (1). The most common sites of occurrence are the sacrococcygeal region and the ovaries (2). A malignant tumor that arises in a pre-existing mature teratoma is called teratoma with malignant transformation (3). Malignant transformation occurs in 1–3% of all mature teratomas (4). Squamous cell carcinoma is the most common form of transformation (5). Transformation into other types of tumor, including thyroid carcinoma, adenocarcinoma and carcinoid tumor, has also been reported (5,6). Carcinoid tumors are slow-growing tumors, originating from neuroendocrine cells, which are classified into four categories: i) Insular; ii) trabecular; iii) strumal; and iv) mucinous types (7,8). Carcinoids are most commonly found in the ileum and appendix. While mature cystic teratomas are benign tumors, carcinoid tumors of the ovary are considered to be malignant and are occasionally associated with metastases (7,8). In previous studies, the majority of carcinoid cases of the ovary were associated with carcinoid syndrome, which leads to symptoms such as, cutaneous flushing, diarrhea, bronchoconstruction and right-sided cardiac valve disease (9–11). Carcinoid tumours have variable clinical behaviour. While they are considered to be slow growing, a metastatic disease is often stated on the initial presentation of carcinoids (12). The overall 5-year survival rate for patients with carcinoids regardless of location is 44–56% (13). The presence of regional and distant metastases are associated with a worsening in the prognosis. Hormone and vasoactive amine secretion from the carcinoid tumor cells cause carcinoid syndrome. Serotonine, tachykinine, prostaglandines and histamine are the main secretions of carcinoids. The secretion of these substances cause symptoms as flushing, diarrhea, bronchial obstruction and heart failure (14). Surgery is the main treatment for carcinoid tumors and previous cases of carcinoids arising in mature teratomas of the retroperitoneum and ovary, which were successfully treated by surgical resection have been reported in the literature (15–17). The current study describes an insular and trabecular variant of carcinoid tumor arising in a mature cystic teratoma, which is notable due to the rarity of this occurrence. This study was approved by the ethics committee of Bezmialem Vakıf University (Istanbul, Turkey) and written informed consent was obtained from the patient.

Case report

A 75-year-old woman (gravidity=6, parity=6, curettage=3) suffering from groin pain was referred to the gynecology clinic at the Faculty of Medicine, Bezmialem Vakıf University in August 2013. An adnexal mass was located during the physical examination. Pelvic magnetic resonance imaging revealed an 8×7-cm mass in the right ovary, compatible with a dermoid cyst. The patient was postmenopausal for 30 years, had undergone cholecystectomy 14 years prior and appendectomy 57 years prior. The tumor markers were negative and right salpingo-oophorectomy was performed.

Macroscopic examination revealed a cystic mass filled with viscous sebaceous material, measuring 10×9.5×8 cm. The cyst wall also contained bony structures, which indicated a teratomatous origin. Multiple samples were obtained from the specimen and evaluated. On the histological sections, mature squamous and respiratory epithelium and mature mesenchymal components were identified. The cyst wall contained a 4.5-mm2 area consisting of neoplastic cells forming nests, cords and trabeculae. The neoplastic cells were uniform, with small round nuclei without atypia or mitotic activity, as observed by hematoxylin and eosin staining in Fig. 1A–C.

Figure 1. Hematoxylin and eosin staining of (A) respiratory epithelium on the surface, nests and cords of neoplastic cells in the cyst wall; (B) trabecular structures of carcinoid, mucous glands and fibroadipous tissue in teratoma; and (C) neoplastic cells forming nests and trabeculae. Magnification, x100. (D) Diffuse intense immunoreactivity of synaptophysin (magnification, x100); (E) diffuse immunoreactivity of chromogranin (magnification, x100); and (F) proliferative activity assessed by Ki-67 (magnification, x400).

Immunohistochemical staining, including synaptophysin, chromogranin and Ki-67 were applied. Diffuse intense immunoreactivity of synaptophysin (Fig. 1D) and chromogranin (Fig. 1E) was present, indicating that the tumor was of neuroendocrine origin. The proliferation index was determined by Ki-67 expression and was 2% (Fig. 1F). Thus, the tumor was classified as low grade (18). Morphological and immunohistochemical findings indicated a carcinoid tumor arising in the wall of the mature cystic teratoma.

The patient received no further treatment, and no recurrence was observed after 11 months of follow-up examinations.

Discussion

Malignant transformation is a rare complication of mature cystic teratomas (19). Carcinoid tumors are rare and have been presented as case reports previously (20,21). Carcinoid tumors in ovarian and testicular teratomas are considered to be derived from neuroendocrine cells of the gastrointestinal or respiratory epithelium (17,22). In the present case, the carcinoid tumor was located near respiratory epithelium. Serotonin, histamine, catecholamines, prostaglandin and vasoactive peptides are frequently secreted by carcinoid tumors predisposing affected patients to carcinoid syndrome. However, the patient in the current case study did not present with carcinoid syndrome. Carcinoid tumors arising from teratomas have been reported in postmenopausal cases in previous case reports (6,23). The patient in the present report was also postmenopausal. Cyst wall invasion, intraoperative rupture of the cyst and tumor seeding are defined as poor prognostic factors in malignant transformation of teratomas (24). Carcinoid tumors arising in mature teratomas are tumors with low malignancy potential (17). However, the prognosis and clinical behavior of these tumors have not yet been clarified (25). Without resection of the tumor, the risk of malignant transformation increases with time. All suspected areas in the cyst walls should be sampled in order to define these unusual rare neoplasms. In the present case report, the tumor was in a small area in the cyst wall and completely resected. This case was notable due to the rarity of this occurrence.

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