1 INTRODUCTION

Teratomas are uncommon neoplasms that comprise a mixed dermal elements derived from the three germ cell layers.^{1, 2} They can be mature benign without malignant cells or immature with malignant cells.³ They commonly occur in the sacrococcygeal region in children and in gonads in adults especially in women. The retroperitoneal localization is not common. It constitutes less than 4% of all extragonadal teratomas.⁴ In addition, those benign tumors are most often asymptomatic. In most cases, they are identified incidentally.

In this paper, we report a case of mature extra-gonadal retroperitoneal teratoma occurring in a young adult man. We focus on clinical, radiological, biological, and histological presentations, and we realize a literature review of this rare location.

2 SEARCH STRATEGY

3 CASE PRESENTATION

3.2 Differential diagnosis, investigations, and treatment

Abdominal computerizing tomography (CT) scan showed a heterogeneous retroperitoneal mass of the left flank, with mixed components of water, fat, and calcium (Figure 1). It measured 9 cm in long axis, exerting a mass effect on the left ureter, and responsible for a slight dilatation of excretory cavities. The chest X-ray was normal. There was no other suspected location.

The operability assessment was normal. World Health Organization performance status grade was 0. Hemoglobin level was 14.2 g/dl. Renal function was normal, and urines were sterile on cyto-bacterial examination.

An exploratory midline laparotomy for mass resection was planified. Per-operative exploration showed a left retroperitoneal mass of 8 cm long axis, blowing the left mesocolon (Figure 2), and having a thick and inflammatory capsule. A careful left colic mobilization was performed after incision of the left mesocolon, in an avascular zone, in contact with the mass, from inside to outside. Gerota's fascia was intact. The mesocolic gap was sutured to avoid internal herniation later. The vascularity of the colon was not compromised. Enucleation of the mass was performed (Figure 3).

3.3 Outcome and follow-up

Post-operative course was simple. The patient was discharged home on the third postoperative day.

Pathological examination showed a heterogeneous mass on section, with adipose lobules, cartilaginous hair and mucus, and covered with false membranes (Figure 4). On microcopy, there were 3 types of epithelium; a keratinizing squamous epithelial, a respiratory type, and a secretory mucous gastric one with an extensive inflammatory remodeling (Figure 5). There was no immature component. The diagnosis of mature cystic teratoma was made. After 03 months of follow-up, the patient reported pain disappearance with a normal digestive transit.

4 DISCUSSION

Our case is of interest because it provides an overview of a rare extra-gonadal mature teratoma occurring in a young adult man in the retroperitoneal region.

Teratomas develop from the three embryonic germ layers.¹ There are two variants: cystic teratomas which are composed of fully mature elements and are usually benign and solid teratomas which are more likely to be malignant.^{9, 10} Primary retroperitoneal teratomas constitute 1 to 11% of retroperitoneal neoplasms and are most commonly found in neonates and in young adults.² They occur in female twice than male. Benign teratomas are usually asymptomatic.¹¹ Symptoms are related to the increase in volume causing compression of surrounding structures .^{5, 12} As in our case, patient may present with back or abdominal pain, genito-urinary, or gastro-intestinal symptoms. Lower extremity or genital edema may be also noted.² Additionally, some complications may happen, such as abscess or rupture causing peritonitis.^{7, 13}

Physical examination may found a palpable abdominal mass, a tenderness, and distension.^{2, 14} This mass may be confused with other tumors such as renal cysts, adrenal tumors, gonadic tumors, fibromas, hemangiomas, enlarged lymph nodes, and sarcomas. Imaging investigations can help guide the diagnosis. Abdominal ultrasound can reveal tumors with cystic and solid components and echogenic spots with acoustic shadows with some limitations in detecting fat and calcifications.¹⁴ Hence, CT scan offers a better identification of fat, sebum, and adipose tissue. Therefore, identification of sebum on CT is very suggestive for teratoma.² However, the diagnostic accuracy remains histological.^{8, 15} Surgical resection is of greatest importance for both diagnosis and treatment. Midline or transverse incision is used for most patients. When possible, laparoscopic methods may be an excellent alternative but requires an adequate laparoscopic skills.¹⁶ Usually, primary retroperitoneal teratoma does not infiltrate adjacent structures and can be fully resected without significant complications. Prognosis is excellent in patients with complete resection of benign teratomas. Malignant transformation of mature teratoma is uncommon. Also, malignant teratomas with germ cell elements may have a grim prognosis, hence, the interest of a complete surgical resection with a histological confirmation.¹⁷

Through our literature review, we came across 6 cases of primary mature extra-gonadal retroperitoneal teratomra occurring in adult patients. They are presented in Table 1.^3-8 The age of patients ranged from 23 to 50 years with an average of 29 years. They were 6 females. Abdominal pain was the most common first clinical presentation. Abdominal scan was performed for all patients. The mass was localized in the left retroperitoneal region for most of them. Complications were noted in two cases, one with abscess, and one with intra spinal extension.

Regarding therapy, laparotomy was performed in 5 cases and laparoscopy in one case. Simple outcome was noted in all cases.

5 CONCLUSION

Primary retroperitoneal mature teratomas with extra-gonadal location are rare especially in young adult man. They are usually identified when they exert a mass effect on adjacent structures. Surgical resection remains the mainstay of therapy, and histological examination is essential for definitive diagnosis. Patients with complete resection of a benign teratoma have an excellent prognosis.

Additionally, we have highlighted teratoma as a differential diagnosis of retroperitoneal mass, and we emphasized the importance of complete resection to confirm the diagnosis and to avoid complications and malignancy transformation.

AUTHOR CONTRIBUTIONS

All the authors participated in the design of the study and wrote the manuscript. All authors read and approved the final manuscript. Mohamed Farès Mahjoubi has drafted the work. Ghassen Hamdi Kbir has substantively revised the work. Mohamed Maatouk, Sohaib Messaoudi, and Bochra Rezgui have made substantial contributions to the literature research. Mounir Ben Moussa has made substantial contributions to the conception of the work.

CONFLICT OF INTEREST

The authors have no conflict of interests.

ETHICAL APPROVAL

Our locally appointed ethics committee “Charles Nicolle Hospital local committee” has approved the research protocol and informed consent has been obtained from the subject.

HUMAN AND ANIMAL RIGHTS

Our study complies with the Declaration of Helsinki.

CONSENT

Written informed consent was obtained from the patient.