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Seth G.S. Medical College and K.E.M. Hospital, Mumbai , India

Case of the Month

< Case No. 66 : October 2025 >

Seminoma in an Inguinal Ectopic Testis with Aggressive Retroperitoneal Invasion: A Demonstration of Classic Imaging and Pathologic Correlation

Contributed by Sharzil Shaikh

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Introduction :

Testicular seminoma is the most common malignant tumour of the testis and classically manifests as a painless mass [1]. A major risk factor is cryptorchidism, which increases the risk of malignancy by eight times [1, 2]. Radiologic evaluation with high-frequency ultrasonography (US) is critical for the initial diagnosis, while computed tomography (CT) provides valuable information for staging, including the presence and size of retroperitoneal lymph nodes [1, 3]. Seminomas typically metastasize to the retroperitoneum; left-sided tumors drain to the para-aortic and preaortic lymph nodes [3, 4].

This is a case of a seminoma arising in an inguinal ectopic testis that presented with a groin mass and was found to have extensive retroperitoneal disease with direct organ invasion demonstrating the classic imaging and pathologic features described in the literature. However, there was no abdominal lymphadenopathy.

Clinical Profile:

A 37-year-old man presented with complaints of a left groin swelling since childhood, which had gradually increased over the past year. It was associated with mild, dull, aching pain. The overlying skin was normal, and there were no other similar swellings. The patient had been diagnosed with left ectopic testis since childhood.

On examination, the swelling was firm and non-tender. Cough impulse was absent. The left hemiscrotum was empty. No palpable lymph nodes were noted.

Based on these findings, inguinoscrotal ultrasound examination was advised. This was followed by abdominal ultrasound examination, contrast-enhanced CT (CECT) of the abdomen, and MRI of the abdomen.

Radiological Findings-

Ultrasonography of the inguinoscrotal region (Figures 1, 2) shows a large, bulky left testis measuring 6 × 5 cm with multiple ill-defined, heterogeneously hypoechoic areas. On Doppler study, the lesion shows normal to increased blood flow. The left testis is absent in the hemiscrotum, while the right testis is normal. The heterogeneous appearance is suspicious for malignancy; although seminomas are usually homogeneously hypoechoic, larger tumours can become heterogeneous [1, 6].

Figure 1,2: Ultrasonography of the inguinoscrotal region shows a large bulky left testis in the left inguinal region measuring 6x5 cm with multiple ill-defined heterogeneously hypoechoic areas within. On Doppler study, it shows normal to increased blood flow.

Abdominal ultrasonography (Figure 3) shows a large homogeneous mass in the left para-aortic region, invading the lower pole of the left kidney and upper ureter, resulting in moderate hydronephrosis. Vessels to the left kidney are seen coursing through the lesion.

Figure 3: Ultrasonography of the abdomen shows a large homogenous mass in left para aortic region which invades the lower pole of left kidney and upper ureter leading to moderate hydronephrosis. Vessels to the left kidney pass through the lesion.

Contrast enhanced CT scan of the abdomen and pelvis (Figure 4), demonstrates a well-defined, homogeneously enhancing mass (7 × 4.5 cm) in the left inguinal region consistent with a malignant ectopic testis. Another large, ill-defined, homogeneously enhancing lesion is noted in the left para-aortic region (Figures 5, 6), the characteristic primary drainage site for a left testicular tumour. The mass shows aggressive features with direct invasion of the left kidney and ureter, resulting in moderate hydronephrosis. There is encasement of the aorta and left renal artery without obstruction. The aorta is displaced anteriorly.

Figure 4: Contrast enhanced CT scan of the abdomen and pelvis shows a well-defined, homogenously enhancing mass (7x4.5cm) in the left inguinal region, consistent with the malignant ectopic testis.

Figure 5, 6: There is a large, ill defined, homogenously enhancing lesion in the left para-aortic region, the characteristic primary drainage site for a left testicular tumour. The mass demonstrates locally aggressive features in the form of direct invasion of the left kidney and ureter, resulting in moderate hydronephrosis. There is encasement of the aorta and left renal artery without obstruction, THe aorta is displaced anteriorly..

MRI of the abdomen (Figures 7, 8) demonstrates diffusion restriction on DWI with corresponding low signal on ADC.

Figure 7, 8: MRI of the abdomen- the lesions shows diffusion restriction on DWI with corresponding drop on ADC.

Radiological diagnosis:

Seminomatous tumor in an ectopic testis with metastasis

Laboratory investigations:

Serum Tumour Markers: Lactate dehydrogenase (LDH) was significantly elevated at 1,100 U/L. Beta-human chorionic gonadotropin (β-hCG) was elevated at 350 mIU/ml. Alpha-fetoprotein (AFP) was within normal limits.

Final diagnosis:

Seminoma with locally advanced spread.

Management:

The patient was diagnosed with locally advanced seminoma (Stage IIIB by IGCCCG criteria). The finding of direct renal invasion is a rare but serious complication. The patient was referred to medical oncology for primary systemic chemotherapy with a BEP regimen. It is important to note that testicular seminoma is highly curable even at advanced stages and his prognosis remains favourable with appropriate treatment [1].

Complete excision of the mass was performed.

Figure 9: Gross specimen is solid and fleshy.

Discussion:

1. Imaging Diagnosis and Staging: This case underscores the algorithm for managing a testicular mass. Ultrasonography is the initial modality, confirming the intracanalicular location of the ectopic testis and raising suspicion for malignancy. CECT is then critical for staging, accurately depicting the large, homogeneous retroperitoneal mass and its locally invasive behaviour [1, 3, 4].Homogeneous enhancement is a classic feature of seminomatous metastases, which may remain homogeneous even when bulky. Based on these features, lymphoma is considered as a differential diagnosis.

2. Pattern of Spread: The location of the metastasis is anatomically precise. The mass was in the left para-aortic region, which is the predictable lymphatic drainage pathway for a left-sided testis [3, 4]. The homogeneous attenuation on CT is a fundamental characteristic of seminoma, reflecting its uniform histologic architecture [1, 4].

3. Serologic Correlation: The tumor marker profile is pathognomonic. The elevated LDH reflects tumour burden, the mildly elevated β-hCG can be seen in seminoma (often due to syncytiotrophoblasts), and the normal AFP is essential for confirming a pure seminomatous histology [1, 5].

4. Pathologic Correlation: The histologic findings of "sheets of monotonous cells with intervening thin fibrous septa" directly explain the homogeneous appearance of the tumour on cross-sectional imaging [1, 7].

This case also highlights an unusual presentation of seminoma with direct renal invasion, moving beyond typical lymphatic metastasis. Radiologists must be aware of this aggressive potential, especially in cases of delayed diagnosis arising from cryptorchidism.

Timeline

References:

1. Marko J, Wolfman DJ, Aubin AL, Sesterhenn IA. Testicular Seminoma and Its Mimics: From the Radiologic Pathology Archives. RadioGraphics. 2017;37(4).

2. Wood HM, Elder JS. Cryptorchidism and Testicular Cancer: Separating Fact from Fiction. J Urol. 2009;181(2):452-461. (Cited in RSNA article).

3. Kreydin EI, Barrisford GW, Feldman AS, Preston MA. Testicular cancer: what the radiologist needs to know. AJR Am J Roentgenol. 2013;200(6):1215-1225. (RSNA article ref #11).

4. Sohaib SA, Koh DM, Husband JE. The Role of Imaging in the Diagnosis, Staging, and Management of Testicular Cancer. AJR Am J Roentgenol. 2008;191(2):387-395. (RSNA article ref #3).

5. Nazeer T, Ro JY, Amato RJ, Park YW, Ordonez NG, Ayala AG. Histologically pure seminoma with elevated alpha-fetoprotein: a clinicopathologic study of ten cases. Oncol Rep. 1998;5(6):1425-1429. (RSNA article ref #12).

6. Schwerk WB, Schwerk WN, Rodeck G. Testicular tumors: prospective analysis of real-time US patterns and abdominal staging. Radiology. 1987;164(2):369-374. (RSNA article ref #20).

7. Howitt BE, Berney DM. Tumors of the testis: morphologic features and molecular alterations. Surg Pathol Clin. 2015;8(4):687-716. (RSNA article ref #16).

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