Monodermal teratoma: Three case reports and review of literature

Abstract

BACKGROUND

The incidence of monodermal teratomas of the reproductive system is low, and most doctors lack adequate understanding, which can easily lead to missed diagnoses and/or misdiagnosis. Therefore, it is important to fully understand the clinical characteristics, diagnosis, differential diagnosis, and treatment of monodermal teratomas of the reproductive system.

CASE SUMMARY

Case 1: A 14-year-old boy was admitted to the hospital with a right testicular mass for 1 wk and underwent surgical resection. He was finally diagnosed with right testicular monodermal teratoma with no special postoperative discomfort. Case 2: A 40-year-old woman was admitted to the hospital for uterine abnormalities indicated by ultrasound 20 d prior and underwent laparoscopic surgery. She was finally diagnosed with a left ovarian monodermal teratoma with a satisfactory postoperative quality of life. Case 3: A 49-year-old woman was admitted to the hospital with a pelvic mass that was discovered on B-ultrasound a week prior and underwent laparoscopic resection of the left adnexa. She was finally diagnosed with left ovarian monodermal teratoma, and her postoperative quality of life was satisfactory.

CONCLUSION

Monodermal teratoma is a rare tumor whose clinical manifestations are primarily benign. Simple surgical resection of the tumor is effective.

Key Words: Teratoma; Reproduction; Ovary; Testis; Case report

Core Tip: Monodermal teratomas are rare tumors characterized by their organizational structure originating from a single germ layer-the endoderm, mesoderm, or ectoderm. This teratoma is most commonly found in the ovaries, followed by the testes. Case reports and case series on monoblastic teratoma have been relatively sparse in the published literature. The diagnosis and treatment of two cases of ovarian monoblastic teratoma and one case of testicular monoblastic teratoma are reported in this paper, and their clinical characteristics are described in combination with a brief literature review to deepen the understanding of this disease.

INTRODUCTION

Monodermal teratoma is a type of tumor formed by the abnormal development of embryonic tissues (endoderm, mesoderm, and ectoderm), which originates from pluripotent germ cells and embryonic cells. Owing to abnormal cell proliferation and differentiation, multiple types of tissues are mixed, which may include skin, hair, bone, muscle, and neuroepithelium, among others[1,2]. Teratoma usually occurs in the gonads, with only 15% occurring in the external gonads[2]. It includes three types: Mature teratoma, immature teratoma, and monodermal teratoma[3]. Monodermal teratoma is a rare type of teratoma whose tissue structure originates from a single germ layer (endoderm, mesoderm, or ectoderm)[4]. The ovary is the most common site of occurrence[5], followed by the testis[6], but there are also literature reports of monodermal teratoma occurring at other sites[7-11]. Given the low incidence of monodermal teratoma, relatively few case reports and case series have been published to date. In this paper, three cases of monodermal teratoma of the reproductive system were reported to deepen our understanding and recognition of this disease.

CASE PRESENTATION

Chief complaints

Case 1: Right testicular mass for 1 wk.

Case 2: Ultrasound showed abnormal uterus for 20 d.

Case 3: B-ultrasound found pelvic mass for 1 wk.

History of present illness

Case 1: A 14-year-old male child was diagnosed with a peanut-sized right testicular mass accompanied by pain 1 wk prior without an obvious cause and did not receive further treatment. Presently, the child was admitted to our hospital for further diagnosis and treatment. He was admitted to our department with the diagnosis of "right testicular mass".

Case 2: A 40-year-old female patient with decreased menstrual volume and occasional dysmenorrhea 20 d prior underwent ultrasound examination in our hospital, indicating that: (1) Uterine adhesion; (2) uterine adenomyosis; (3) cystic mass in the right ovary, considering the possibility of a physiologic cyst; (4) abnormalities in the lower anterior wall of the uterus, considering the possibility of diverticulum and hematosis due to a caesarean section incision; and (5) uterine effusion. The patient did not undergo further treatment, and now she presented to our hospital for further diagnosis and treatment. The outpatient was admitted to our department with the diagnosis of "intrauterine adhesions".

Case 3: A 49-year-old female patient was found to have a pelvic mass by B-ultrasound in the Second People's Hospital of Guizhou Province 1 wk prior. The patient did not receive further treatment. Now she was admitted to our hospital for further diagnosis and treatment, and a B-ultrasound was performed to show: (1) A solid mass in the left adnexal area, with a left ovarian tumor considered; and (2) Pelvic and abdominal fluid. The outpatient clinic entered our department with the diagnosis of "pelvic mass: Left ovarian Ca." The clinical features of the 3 patients are shown in Table 1.

Table 1 Clinical characteristics.

Case number	Sex/Age	Tumor location	Symptoms	Tumor marker	Hyperthyroidism	Maximum tumor diameter in cm	Form	Boundary
1	M/14	Right testis	Testicular mass	Normal	No	1.5	Roundness	Clear
2	F/40	Right ovary	Hypomenorrhea	Normal	No	4.6	Ellipsoid	Clear
3	F/49	Left ovary	Unspecific	CA125, HPV51 (+)	No	7.0	Ellipsoid	Clear

CA125: Cancer antigen 125; F: Female; M: Male; HPV51: Human papillomavirus type 51.

History of past illness

Case 1: Past history is not special.

Case 2: Cesarean section delivered in a local hospital in Chongqing in 2001 due to improper fetal position (specific details are unknown); in 2008, a cesarean section was performed in Jinjiang Branch Hospital of Fujian Province due to an improper fetal position (specific details are unknown); in 2020, hysteroscopy was performed in Zunyi Medical University due to intrauterine adhesions (details unknown); in 2021, due to intrauterine adhesion and bilateral fallopian tube obstruction in Beijing Weiren Hospital of Traditional Chinese Medicine, laparoscopy combined exploration and implantation of a uterine stent was performed, and she was discharged 1 mo after surgery (specific details are unknown).

Case 3: A 1-year history of hypertension was treated by oral telmisartan tablets (specific details unknown).

Personal and family history

None of the 3 patients had any special personal history, and were all non-smokers and non-drinkers with no other harmful habits.

Physical examination

Case 1: Body temperature: 36 °C, pulse: 80 beats/min, blood pressure: 13.3/9.5 kPa, respiration: 20 beats/min, penis development was fine, testis could be reached by bilateral scrotum, and the right testicle had large or small clumps, which were hard to the touch and could be pushed, without redness or swelling. There was no palpable mass in the bilateral groin area, no abnormal appearance of the anus, no visible urethral orifice, and no purulent and bloody secretions at the external urethral orifice. The physiological reflex was present, but the pathological reflex was not induced.

Case 2: Normal vulva development, married type without birth, open vagina, little white secretion, no odor, smooth cervix, tough, no lifting pain, uterine posterior position, normal size, medium quality, with mild tenderness, bilateral appendages without palpation, and obvious abnormalities.

Case 3: Vulvar married delivery, vaginal patency, normal mucosa, a small amount of secretions, no obvious abnormalities in posterior vaginal fornix, cervical lift pain, cervical smooth, uterine anterior position, atrophy, regular shape, clear boundary, range of motion, tenderness, and unclear palpation of both appendices.

Laboratory examinations

Case 1: The level of alpha fetoprotein (AFP), a tumor marker, was normal.

Case 2: Tumor markers such as cancer antigen (CA) 125, CA 19-9, and human epididymal secreted protein were normal.

Case 3: Tumor markers such as CA125 were elevated and the patient showed positivity for human papillomavirus type 51. Carcinoembryonic antigen, AFP, CA153, CA19-9, CA72-4, and CA24 were normal.

Imaging examinations

Figure 1 shows the ultrasound images of the 2 female patients with ovarian monodermal teratoma, while the imaging data of the patient with testicular monodermal teratoma was incomplete and not included. Vaginal B-ultrasonography in 1 patient showed an echoless area in the right ovary measuring 28 mm × 39 mm × 46 mm, with a clear boundary and no color blood flow signal, and was considered a physiological cyst. In the other case, vaginal B-ultrasonography showed a solid mass in the left adnexal area measuring 70 mm × 51 mm × 54 mm, with a clear boundary and abundant blood flow signals. Hence, ovarian cancer was suspected.

Figure 1 Ultrasound findings. A: Right ovarian echoless area with clear boundary; B: No color blood flow signal was found in the sac wall of the right ovarian anechoic region; C: Solid mass in the left adnexal area with clear boundary; D: Abundant color blood flow signals were seen around the solid mass in the left adnexal area.

FINAL DIAGNOSIS

Case 1

Monodermal teratoma of the right testis.

Case 2

Right ovarian monodermal teratoma.

Case 3

Left ovarian monodermal teratoma.

TREATMENT

Case 1

The patient underwent resection of the right testicular lesion plus scrotoplasty, followed by postoperative hemostasis, detumescence, fluid rehydration, and symptomatic supportive treatment.

Case 2

The patient underwent uterine laparoscopy combined with lower uterine adhesiolysis, right ovarian cyst removal, and pelvic adhesiolysis and was given antibiotics, fluid rehydration, and symptomatic supportive treatment after surgery.

Case 3

The patient underwent laparoscopic left adnexectomy plus intestinal adhesion-release and was given postoperative fluid rehydration, antibiotics, and symptomatic supportive treatment.

OUTCOME AND FOLLOW-UP

All 3 patients underwent surgical treatment. Figure 2 shows the postoperative pathological images of 3 patients. All 3 patients were successfully operated on and were actively followed up after surgery. No other special treatment was administered to the patients, and they were followed up for 12–20 mo (mean follow-up duration: 16 mo). No recurrence or metastasis occurred in any patient.

Figure 2 Pathological findings. A: Histological section of the epidermoid cyst of the right testicle showing the structure of the cyst (hematoxylin & eosin × 1); B: The cyst wall is composed of squamous epithelium surrounding the lamellar keratin layer, and there is a large amount of keratin in the cyst cavity (hematoxylin & eosin × 10); C: Histological section of the right ovarian cyst showed a large amount of thyroid follicular tissue (hematoxylin & eosin × 10); D: Histological sections of the left ovary showed a large amount of thyroid follicular tissue (hematoxylin & eosin × 10)

DISCUSSION

Teratoma is a rare tumor[1] whose etiology is not yet fully understood. Currently, it is believed that teratomas are formed because of abnormal embryonic development[1,12], which may be related to genetic factors, chromosomal aberrations, and embryonic development disorders. Teratomas can occur at any age, but is more common in children and adolescents[12]. Teratoma usually occurs in the gonads, including the testis and ovaries, but it has also been reported in the brain, thymus, lung, bone, and midline[2,13]. In some cases, the teratoma may recur and metastasize to other organs such as the lungs, liver, peritoneum, and lymph nodes[14,15], and the severity of recurrence and metastasis may affect the patient's prognosis and treatment plan. Thus, regular monitoring and treatment are key to improving the control rate of recurrence and metastasis.

Monodermal teratoma[4] is a rare subtype of the teratoma, characterized by the formation of only one embryonic layer (endoderm, mesoderm, or ectoderm) of cell tissue. If the tumor originates from the endoderm, its tumor composition may include organs such as the respiratory tract and the digestive tract. If it comes from the mesoderm, it may contain muscle, bone, blood vessels, and other related tissues. If derived from the ectoderm, it may contain skin and nerve tissue. Published literature on similar lesions can be traced back to the late 19^th and early 20^th centuries[16]. However, owing to the relatively low incidence of these diseases, academic studies and case reports are scarce. Monodermal teratoma is mainly found in reproductive organs such as the ovaries or testis, but some reports have shown that that this disease may also appear in other body parts such as the brain, spine, placenta, and pelvic cavity[7-11]. Most monodermal teratomas appear as benign lesions[17], but may further develop into malignant tumors. The age range of patients is wide, ranging from infants to older patients, but it is mainly concentrated in women of reproductive age and young men. Surgical resection is the preferred treatment for monodermal teratomas to remove the tumor tissue as much as possible. Preoperative or postoperative radiotherapy and chemotherapy can be combined.

Monodermal teratoma symptoms[18,19] may vary depending on the site and type of lesion, but usually include the following manifestations: (1) Mass: Monodermal teratoma usually forms a palpable mass; (2) Pain: The lump may cause pain or discomfort, especially if it is located near organs or nerve tissue; (3) Compression symptoms: If the tumor increases and compresses surrounding tissues or organs, related symptoms may appear, such as dyspepsia, dyspnea, and urinary tract obstruction; and (4) Endocrine disorders: Some monodermal teratomas may produce hormones, leading to menstrual changes, hyperthyroidism, and other endocrine manifestations. The symptoms of monodermal teratoma are affected by the location and size of the tumor and may vary from individual to individual. Because the symptoms of this tumor are non-specific, missed diagnosis and/or misdiagnosis are both likely.

Struma ovarii is the most common type of monodermal teratoma and usually occurs in middle-aged women[20]; occurrence in prepubertal patients is rare. In this paper, the average age of the 2 patients with struma ovarii was 43-years-old, and both of them were middle aged. It is mainly composed of thyroid tissue, and only when the proportion of thyroid tissue exceeds 50%[21] is this lesion called an ovarian goiter. This disease is a specific form of mature teratoma, which accounts for 0.5%–1% of all ovarian tumors[22]. Most ovarian goiters are benign, but in 5%–10% cases, the diseased thyroid tissue may undergo malignant transformation[23-25]. Common malignant types include papillary and follicular cancers of the thyroid gland, while medullary, poorly differentiated, and undifferentiated cancers are relatively rare. Studies have found that recurrence and metastasis of benign goiter are relatively low (metastasis rate: 5%–10%)[26]; malignant goiter has a higher risk of recurrence and metastasis (metastasis rate: 52.94%)[19,27] and should be closely monitored after surgery.

Most patients with struma ovarii are asymptomatic, and the condition may be accidentally found upon imaging examinations or operations[28]. Some patients may seek medical treatment because of abdominal pain, bloating, mass, abnormal uterine bleeding, or other uncomfortable symptoms[29]. In addition, patients may also have ascites and elevated CA125 levels[30]. Hyperthyroidism can be another manifestation[19] owing to the fact that the thyroid tissue is located within the ovarian goiter and induces the same pathophysiological changes as the thyroid. In this study, both female patients had goiter that was detected by chance during examination, as neither had obvious symptoms of hyperthyroidism. One patient was found to have minimal ascites and elevated CA125 during examination. On imaging studies[17], ovarian goiter usually presents as a polycystic mass with no or moderate wall enhancement and may show a high attenuation lesion reflecting thyroid tissue. The comprehensive evaluation of diffusion-weighted magnetic resonance imaging (MRI) and computed tomography (CT) findings[17] can improve the accuracy of the preoperative diagnosis of ovarian goiter. In histopathological examination[21], thyroid tissue accounted for > 50% ovarian goiter. In differential diagnosis[20], ovarian goiter needs to be distinguished from physiological ovarian cysts, salpingo-ovarian abscesses, hydrosalpinx, endometrioma, ectopic pregnancy, and ovarian tumors.

Preoperative laboratory examination of struma ovarii is often difficult to confirm[17], and it is difficult to distinguish it from the disease, which needs to be further diagnosed by postoperative pathology. For benign goiters, the conventional treatment is tumor resection. For malignant goiter, patients who do not consider fertility preservation can choose radical surgery, including hysterectomy, bilateral adnexectomy, thyroidectomy, and radioactive iodine therapy[23-25]. For patients who need to preserve fertility, adnexectomy on the diseased side, combined with thyroidectomy and radioactive iodine therapy can be chosen[20]. Plasma thyroglobulin can be used as a recurrent marker of malignant goiter for continuous monitoring. However, recurrence and metastasis of goiter after surgery are both possible, and the patients should be monitored regularly after the operation. Details of these cases are summarized in Table 2[31-35]. In this study, 1 of the patients had a preliminary diagnosis of a biological cyst before surgery, so a relatively simple tumor resection was chosen as the surgical method. The other patient was speculated to have malignant lesions during the preoperative examination. Due to the patient’s fertility needs, the surgical method was selected to remove the adnexa on the lesion side. Postoperative pathological examination results of both female patients showed ovarian goiter, and no further treatment was required after surgery. No recurrence or metastasis was found during the follow-up.

Table 2 Features of ovarian monodermal teratoma in previously reported cases.

Number [Ref.]	Year	Age	Tumor location	Ascites	Tumor marker	Transfer	Maximum tumor diameter in cm	Treatment	Recrudescence
1[31]	2023	45	Left ovary	No	CA125 (+)	No	11	Tumor resection	No
2[32]	2023	58	Right ovary	Yes	CA125 (+)	No	15	Tumor resection	No
3[21]	2023	16	Right ovary	No	CA125 (+)	No	35	Tumor resection	No
4[18]	2022	37	Right ovary	Yes	CA125 (+)	No	13	Right adnexectomy	No
5[33]	2022	49,66	Right ovary, Left ovary	Yes	CA125 (+)	No	6.1, 20	Hysterectomy and right salpingo-oophorectomy, Left salpingo-oophorectomy	No
6[34]	2022	38	Left ovary	Yes	CA125 (+)	Bone metastases	3.4	Resection of left ovarian tumor	Recurrence 4 yr after surgery
7[35]	2022	40	Left ovary	Yes	CA125 (+)	No	13.8	Right salpingo-oophorectomy	No

CA125: Cancer antigen 125.

Ovarian tumor resection and radical surgery are the main methods of treatment for ovarian tumors, but they are associated with some risks and complications. Bleeding and infection may occur during surgery, as well as possible damage to adjacent reproductive organs and large abdominal blood vessels[36,37]. There may be tumor recurrence and metastasis after a simple tumor resection. Radical surgery, which usually involves the removal of the uterus, both ovaries, and fallopian tubes, can lead to early menopause and related symptoms such as hot flashes and vaginal dryness that can affect fertility, especially in women of reproductive age. After surgery, patients may experience problems such as pain, fatigue, and indigestion. Long-term effects include sexual dysfunction and reduced quality of life. To avoid associated complications, aseptic techniques should be used during surgery to reduce the risk of infection, and careful procedures should be performed to avoid damage to neighboring organs. After assessing the patient’s overall health before surgery, their vital signs should be monitored during surgery, and appropriate pain management and support recovery after surgery should be provided. For women of childbearing age, surgical options for preserving fertility should be explored[38]. Patient education and psychological support are also key to mitigating long-term effects[39].

The incidence of testicular epidermoid cysts is second only to that of ovarian goiter in monodermal teratomas. In 2016, the World Health Organization tumor classification system defined prepubertal teratoma as unrelated to germ cell tumor[40], which originates from ectodermal tissue, and has been reported in multiple age groups[41-44]. Testicular epidermoid cysts represent 1% of all testicular tumors and are typically benign[45]. Patients usually present with a painless testicular mass that is often detected unintentionally during physical examinations, predominantly on the left side[45]. The patient’s serum tumor markers are commonly within the normal range[42]. In this case series, the adolescent male patient was hospitalized for a right testicular mass. Upon admission, the examination revealed normal AFP levels, a finding that aligns with relevant literature reports.

The diagnosis of epidermoid cysts of the testes is mainly dependent on imaging examination (such as ultrasound and MRI) and tissue biopsy. On ultrasound[46], most cases (60%) had a typical ischemic center and concentric onion ring or target appearance with a complete or incomplete echo edge, whereas Doppler ultrasound showed no blood vessels. The MRI[47] findings typically showed an alternating high-low signal intensity (an orange ring appearance). Histopathological findings usually show a typical, well-defined cyst lined with a fibrous membrane[48]. Testicular epidermoid cysts are usually differentiated from certain diseases[48,49], including testicular cysts, testicular carcinoma, teratoma, yolk sac tumor, rhabdomyosarcoma, sex cord stromal tumor and hemangioma. Imaging examination is helpful for the diagnosis and evaluation of the tumor’s nature. The monodermal teratoma of the testicle is a rare benign tumor. The imaging features of most cases exhibit a certain specificity, which can assist in diagnosis. The preoperative diagnosis holds significant guidance for determining the surgical approach and can effectively prevent unnecessary testicular excision, thereby better preserving the patient’s fertility.

For testicular epidermoid cysts, testicular preservation surgery can be chosen, and only a simple excision or removal of the epidermal tissue within the cyst can achieve the therapeutic effect[41,43]. According to literature reports, no metastasis has occurred after treatment[42], and the recurrence rate is also very low[41,44,49]. The study found that the volume of benign testicular tumors is usually smaller than malignant tumors, generally being no more than 2.8 cm. Therefore, when the volume of the testicular mass is < 2.8 cm and the tumor markers are within the normal range, testicular preservation surgery should be given priority to avoid unnecessary testicular resection[50]. Details of these cases are summarized in Table 3. Although excision of a testicular tumor is better than radical surgery, it may cause some complications such as postoperative infection, bleeding, hematoma formation, and pain in the operative area. Long-term complications may include changes in hormone levels, affected fertility, and psychological effects such as anxiety or depression. A small number of patients may have tumor recurrence and tumor metastasis. In this paper, only the epidermoid cyst of the testis was excised, and no recurrence or metastasis was found 20 mo after the operation.

Table 3 Features of testicular monodermal teratoma in previously reported cases.

Number [Ref.]	Year	Age	Tumor location	Tumor marker	Imaging	Transfer	Maximum tumor diameter in cm	Treatment	Recrudescence
1[51]	2022	25, 58	Left testis, right testis	Normal	Ultrasound shows onion ring appearance	No	1.7, 1.7	Excision testicular tumor, Periodic review	No
2[48]	2022	67	Right testis	Normal	Unspecific	No	12.2	Right orchiectomy	No
3[37]	2020	43	Left testis	Normal	Ultrasound shows onion ring appearance	No	2.7	Left radical orchiectomy	No
4[52]	2020	26	Left testis	Normal	MRI showed onion ring appearance	No	4.8	Excision of left testicular tumor	No
5[45]	2019	62	Left testis	Normal	Ultrasound shows onion ring appearance	No	2.0	Left radical orchiectomy	No
6[53]	2015	11	Left testis	Normal	Unspecific	No	0.83	Excision of left testicular tumor	No

MRI: Magnetic resonance imaging.

Monodermal teratoma occurs in the reproductive system and is usually benign. Surgical excision is the main treatment method, aiming to completely remove the tumor tissue. For low-grade malignant monodermal teratomas, the need for postoperative adjuvant treatment is low. However, in highly malignant cases, adjuvant therapy may be necessary. In addition, chemoradiotherapy is an effective treatment option for metastatic cases. The long-term prognosis of monodermal teratomas of the reproductive system is good, but for highly malignant and metastatic cases, the prognosis is poor. Therefore, early diagnosis and treatment are key to improving patient prognosis. In addition, patients are at risk of recurrence and metastasis after surgery, and the recurrence rate depends on many factors such as tumor stage, treatment, and individual differences among patients. Therefore, the majority of patients can fully recover after receiving appropriate treatment, and recurrence and metastasis rates are low. However, a small number of patients may be at risk of recurrence and metastasis, requiring long-term follow-up and monitoring. Hence, early detection and treatment can improve patient prognosis and survival.

CONCLUSION

Monodermal teratoma is a rare tumor with specific clinical manifestations and imaging features. Early diagnosis and effective treatment are essential to improve patients’ prognosis. Through this case series, we hope to deepen our understanding of monodermal teratoma of the reproductive system, promote the implementation of early diagnosis and treatment, and improve the survival rate and quality of life of patients. Correct diagnosis and differential diagnosis are paramount for appropriate treatment of patients, and more cases need to be evaluated for further analysis to better understand the clinical characteristics of this tumor.