Primary carcinoid tumor arising in a retroperitoneal mature teratoma in an adult


Toshinari Yamasaki md, Department of Urology, Himeji National Hospital, 68 Honmachi, Himeji, Hyogo 670-8520, Japan. Email:


Abstract  An extremely rare case of a primary carcinoid tumor arising in a mature retroperitoneal teratoma is reported. A 53-year-old woman was admitted for further examination of an incidental retroperitoneal mass with calcification. Computed tomography scans demonstrated a tumor with fat, soft tissue and bone densities on the left renal hilum. Surgical excision of the tumor was performed with a preoperative diagnosis of retroperitoneal teratoma. The pathological diagnosis was mature teratoma, including all three germ layers. A carcinoid tumor was evident among teratoid tissues and it was thought to be a teratoma with malignant transformation. The patient did not have a carcinoid syndrome and had an uneventful recovery. She has been followed for 31 months with no recurrence. Carcinoid tumors rarely occur in teratomas of the ovary and the testis and, to our knowledge, this is the first case of carcinoid arising in a retroperitoneal mature teratoma.


Primary retroperitoneal teratomas are rarely seen in adults. The incidence of retroperitoneal teratomas in women is twice that of men, with the ovary the most frequent site in adults, followed by the testis, anterior mediastinum and the retroperitoneal space. A malignant tumor arising in existing a mature teratoma is called teratoma with malignant transformation (TMT). We experienced a case of retroperitoneal teratoma with carcinoid component in an adult woman.

Case report

A 53-year-old woman presented to her local clinic in October, 2000, with a chief complaint of urinary frequency. Abdominal ultrasonography, plain abdominal radiograph and excretory urography showed a tumor with calcification in the left abdominal region and the patient was admitted to the Himeji National Hospital for further examination. A physical examination and routine laboratory data showed no abnormal findings. Endocrinological tests showed no abnormal values in the adrenal system, with normal α-fetoprotein, β-human chorionic gonadotropin, carbohydrate antigen 125 and lactic acid dehydrogenase levels. A plain abdominal radiograph showed calcification on the left renal hilum. Excretory urography revealed no hydronephrosis, but calcification was seen outside of the urinary tract. A computed tomography (CT) scan revealed a tumor of 12 cm in maximum diameter on the median side of the left kidney, with fat, soft tissue and bone densities (Fig. 1). Additionally, the tumor was located between left renal artery and left renal vein. A T2 enhanced magnetic resonance image (MRI) showed low signal intensity areas corresponding to solid adipose tissues, high signal intensity areas corresponding to fibrofatty tissue or muscle and signal void areas corresponding to bones (Fig. 2). A coronal image showed that left adrenal gland was intact and there were no abnormal findings in the bilateral ovary. On CT and MRI scans, the margin of the tumor was well demarcated and clearly separated from other adjacent structures, such as the pancreas and the gastrointestinal tract.

Figure 1.

Plain computed tomography scan showing a multiseptated mass (arrow) that contains different components: fat, soft tissue and bone densities. LK, left kidney.

Figure 2.

T2 enhanced coronal magnetic resonance image demonstrating the three main components of the tumor (arrow). LK, left kidney.

Surgical excision of the tumor was performed in November 2000, with a preoperative diagnosis of retroperitoneal teratoma. As it was difficult to ablate the tumor and renal vessels, the tumor was excised together with the left kidney.

Grossly, the tumor had a well-circumscribed, smooth surface, was yellow-whitish in color and had a primarily solid appearance, measuring 12 × 6 × 6 cm. On excision, bony fragments and adipose tissues were found within the tumor. The cystic portion of the tumor was filled with a thick yellow greasy fluid and hair was present (Fig. 3). The left kidney and left adrenal gland were intact. The tumor was able to ablate the left kidney outside of the renal capsule. There was no continuity in the tumor and the renal parenchyma.

Figure 3.

Macroscopic appearance of the tumor (arrows) and the left kidney (arrowhead). On excision, adipose tissues (white arrow) and bony fragments (black arrow) were found within the tumor. The cystic portion of the tumor was filled with a thick yellow greasy fluid and hair was present (thick white arrow).

Microscopically, mature elements of all three germ layers were present. Cartilage, bone with bone marrow, smooth muscle and fatty tissue were noted. Respiratory epithelium was also observed within the tumor (Fig. 4A). Among the teratoid tissues, carcinoid tumor was present. It was composed of anastomosing cords intermixed with solid nests and was juxtaposed to the respiratory type epithelium (Fig. 4B). The tumor cells were monotonous, small and uniform in size. They had finely glanular eosinophilic cytoplasm and uniform, rounded nuclei. Mitoses were absent (Fig. 4C). Immunohistochemical analysis revealed positivity throughout the component for cytokeratin, chromogranin-A, synaptophysin and neuron-specific enolase. The tumor was diagnosed as a mature teratoma with a carcinoid component. Histologically, there were no abnormal findings in the renal parenchyma.

Figure 4.

(a) Microscopic finding of the tumor revealed trigerminal tissue components. (HE × 40). (b) At right, section of carcinoid tumor showing solid nests and anastomosing cords. At left, columnar epithelium, mucous secretory glands and smooth muscle which resembled bronchus. (HE × 40). (c) Carcinoid tumor with finely granular cytoplasm and uniform rounded nuclei. There were no mitotic figures. (HE × 400).

Work-up at the time of surgery did not show any metastases or any other tumors indicating a metastasis from a primary carcinoid tumor located elsewhere. Carcinoid syndrome was not present. No serum or urine samples were obtained preoperatively for hormonal or polypeptide evaluation. The post operative course was smooth and the patient did well after a follow up period of 31 months.


A teratoma is a neoplasm containing a variety of cell types representative of more than one germ cell layer. Teratomas occur in the ovary, testis, anterior mediastinum, retroperitoneum and parasacral and coccygeal regions in order of frequency. An adult teratomas are characterized as malignant more frequent than childhood teratomas.1

A malignant tumor occurring in an existing mature teratoma is called a ‘teratoma with malignant transformation (TMT)’,2 and this category is applicable to the present case. Malignant transformation is an uncommon complication in a mature teratoma of the ovary, being reported in approximately 2% of cases.3 Squamous cell carcinoma is most frequent with 75–87% and carcinoid is rare with 6% of reported cases.4

A significant number of carcinoid tumors arising in teratomas of the ovary or testis have been reported. Only four cases of carcinoid tumor arising in mature teratomas of the kidney have been reported to date,5–7 but no cases of retroperitoneal pararenal teratoma has been found.

In primary carcinoid tumors, 85% are located in the gastrointestinal tract, 10% in the lung and 5% in unusual sites.8 Carcinoid tumors occurring in ovarian and testicular teratomas are thought to derive from neuroendocrine cells of the gastrointestinal or respiratory epithelium, which are components of these lesions.9 In the present case, the histological features of the lesion juxtaposed to the carcinoid mass prompted us to consider the teratomatous component that had differentiated along a path related to respiratory elements. Endocrine cells may arise by divergent differentiation from the same stem cell that gives rise to the respiratory epithelial elements.

Carcinoid tumors secrete a variety of vasoactive materials which can cause carcinoid syndrome. These include serotonin, histamine, catecholamines, prostaglandins and vasoactive peptides. The manifestations of carcinoid syndrome include facial flushing, edema of the head and neck, abdominal cramps and diarrhea, bronchospasm, cardiac lesions, telangiectasias and increased urinary 5-hydroxyindoleacetic acid (5-HIAA). In the present case, carcinoid syndrome was not present.

In general, when cancer cells extend beyond the tumor capsule, prognosis of TMT is poor.4 Although carcinoid tumors arising in mature teratomas are regarded as tumors of low malignant potential, their prognosis and clinical behavior remain unclear. In cases of primary renal carcinoid tumors, metastases have been described and are usually managed by radical nephrectomy.10 In a case of retroperitoneal teratoma, tumor excision should be performed and should a carcinoid tumor be diagnosed, a search should be conducted for a metastatic lesion and a possible primary elsewhere.

The mean age of TMT tends to be older than that of mature teratoma without malignant transformation. If the mature teratoma left alone long-term, it seems that the frequency of malignant transformation increases. So, we should take the possibility of TMT into consideration in cases of mature teratoma in elder persons.