A Rare Paratesticular Leiomyosarcoma Presenting as a Painless Scrotal Mass in an Elderly Patient: A Case Report

Introduction

Leiomyosarcomas (LMS) are malignant smooth muscle tumors that most commonly occur in the retroperitoneum, uterus, or gastrointestinal tract. In the genitourinary system, soft-tissue sarcomas account for only 1% to 2% of urological malignancies. ¹ Primary LMS are rare, and when they do appear, they are more often found in the kidney or bladder rather than the genitalia. ² Paratesticular LMS, particularly those originating in the scrotum, are exceedingly uncommon with only 110 cases reported to date. ³ Paratesticular LMS may originate from various locations in the scrotal region, including the epididymis, dartos layer, spermatic cord, scrotal skin, and the seminiferous tubules. Depending on the anatomic origin, paratesticular LMS can be further subdivided into 2 categories: cutaneous and subcutaneous LMS. Cutaneous paratesticular LMS arise from the dartos muscle within the genital skin, whereas subcutaneous paratesticular LMS originate from the smooth muscle structures of the genital organ. ⁴

Given their rarity, these tumors can pose a diagnostic challenge, as they often present as painless scrotal swellings and may mimic benign lesions or other soft tissue tumors. ⁵ Accurate diagnosis typically relies on imaging characteristics, surgical excision, and thorough histopathological evaluation, including immunohistochemistry. The current practice for soft tissue sarcoma grading is a system through the Fédération Nationale des Centres de Lutte Contre le Cancer (FNCLCC) which is based on 3 criteria: tumor differentiation, tumor necrosis, and mitotic count. ⁶ We present a case of a paratesticular leiomyosarcoma in an elderly patient, highlighting the diagnostic workup, surgical management, and short-term follow-up outcomes.

Case Presentation

An 84-year-old male with a past medical history significant for diabetes, hypertension, and coronary artery disease presented to the urology clinic with a 5-day history of nonpainful swelling in the left scrotum. He reported no systemic symptoms such as fever, weight loss, or malaise, and denied any recent trauma or radiation exposure. On examination, a firm, nontender mass was palpable in the left scrotum without overlying skin changes. Testicular transillumination was negative.

A high-resolution scrotal ultrasound revealed a paratesticular heterogeneous, hypoechoic mass in the left hemiscrotum measuring approximately 4.1 cm × 3.3 cm × 4.8 cm, with a reniform contour (Figure 1). There were no obvious signs of testicular involvement. Serum tumor markers, including alpha-fetoprotein, beta human chorionic gonadotropin, and lactate dehydrogenase, were within normal limits.

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Figure 1.

Testicular ultrasound of long lateral view with and without Doppler (a, b) and transverse superior view with and without Doppler (c, d) showing a heterogeneous, hypoechoic mass of the left testicle with internal vascularity and measuring approximately 4.1 cm × 3.3 cm × 4.8 cm.

Given the suspicion of a malignant paratesticular mass, the patient underwent a left radical inguinal orchiectomy. Macroscopic examination confirmed a tumor arising from the scrotal soft tissue rather than the testis itself. Histopathology and immunohistochemical staining determined the lesion to be a FNCLCC grade 2 leiomyosarcoma, with positive staining for actin and desmin and negative staining for S-100, consistent with smooth muscle lineage (Figure 2). Postoperative imaging, including contrast-enhanced CT at 1 month and 8 months postoperatively, showed no evidence of locoregional recurrence or distant metastases. The patient remained asymptomatic and in good health at his most recent follow-up. Further, hematoxylin and eosin staining of the mass demonstrated cellular atypia and prominent mitotic figures (Figure 3).

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Figure 2.

Immunohistochemical stain at 200× magnification demonstrating positive staining for smooth muscle actin, consistent with smooth muscle lineage.

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Figure 3.

Hematoxylin and Eosin staining of testicular leiomyosarcoma showing (a) cellular atypia and (b) prominent mitotic figures at 400× magnification.

Discussion

Testicular tumors can be classified as either intratesticular or paratesticular. Paratesticular tumors are generally considered to have a better prognosis compared to intratesticular ones due to the higher likelihood of malignancy within the testis itself.^1,7 Paratesticular tumors are a heterogeneous group of lesions that account for a relatively small percentage of scrotal masses. This region is a complex anatomical area that includes the spermatic cord, testicular tunics, epididymis, fat-ligament-muscle supporting tissues and vestigial remnants. Most paratesticular masses are benign, such as lipomas or epididymal cysts, and malignant transformation is uncommon. ⁸ Leiomyosarcoma, a malignant neoplasm of smooth muscle, from the spermatic cord or the epididymis origin, rarely occurs in the scrotum. When it does, its rarity can lead to a delay in diagnosis due to its nonspecific clinical presentation.

The differential diagnosis for a paratesticular scrotal mass includes liposarcoma, rhabdomyosarcoma, malignant fibrous histiocytoma, and fibrosarcoma. ⁹ Nonneoplastic conditions, such as hematomas or chronic infections, may also mimic neoplasms. Imaging modalities like ultrasound and MRI are valuable for delineating the lesion’s location and characteristics, but histopathological and immunohistochemical analyses are essential for definitive diagnosis.

In the presented case, normal tumor markers helped rule out common testicular malignancies such as germ cell tumors. The immunohistochemical profile, showing strong positivity for smooth muscle markers (actin and desmin) and negativity for S-100 (typically associated with neural crest origin), confirmed the diagnosis of leiomyosarcoma. ¹⁰ The FNCLCC grading system provided additional prognostic information, correlating histological features with potential clinical behavior.

Management of paratesticular LMS typically involves wide local excision or radical orchiectomy to ensure complete tumor removal with clear margins. ¹¹ Additional therapy may be considered depending on tumor size, grade, and evidence of metastasis. Radiation therapy is not effective for leiomyosarcoma; therefore, additional chemotherapy is required in advanced cases although the literature is limited due to the rarity of this condition. ² Long-term surveillance is critical since LMS can recur or metastasize over time.

Given the rarity of this malignant process, definitive guidelines detailing disease prognosis have not been fully established. Existing literature pertaining to extra-testicular leiomyosarcoma is largely defined by independent case reports; however, a 2022 retrospective analysis by Kamitani et al has helped establish a better understanding in determining patient prognosis and disease progression. The strongest prognostic factors are based on the depth of growth and spread in addition to presence of malignancy within surgical margins. Subcutaneous LMS and high-grade tumors are specifically indicated as poor prognostic factors with an increased risk of local recurrence and distant metastasis. ⁴ The exact progression of LMS is yet to be fully elucidated, and even with presumed curative treatment the potential for disease recurrence is still possible. In 2022, Ahwin et al ¹² reported a high-grade paratesticular leiomyosarcoma in a 47-year-old male which reoccurred and metastasized to extremities and lungs 1 year postradical orchiectomy.

In this case, surgical resection was curative at least in the short term as evidenced by imaging studies showing no recurrence at the 3 to 4, 6 or 8 month mark. Although no distant metastases were identified, the patient’s advanced age and comorbidities highlight the importance of individualized follow-up strategies. In reviewing the published literature, numerous cases demonstrated a presentation and diagnostic workup similar to that of the current report. Most patients presented with painless scrotal swelling and a palpable mass, which was subsequently evaluated with ultrasonography and serum testicular tumor markers (alpha-fetoprotein, beta–human chorionic gonadotropin, and lactate dehydrogenase). Assessment for metastasis was typically performed with computed tomography, and management involved radical inguinal orchiectomy followed by confirmation of diagnosis through histopathology and immunohistochemical staining.^12,13,14,15 However, there was notable variation in treatment strategies and follow-up intervals used to monitor for recurrence, underscoring the lack of a standardized approach to management. For example, Naimi et al reported the use of adjuvant 3D-conformal radiotherapy, despite most authors identifying radical inguinal orchiectomy as the preferred treatment. Their decision was based on early data from the Memorial Sloan-Kettering Cancer Center demonstrating the absence of recurrence in irradiated cases compared with surgery alone. ¹⁶ In contrast, other reports described local surgical excision with scrotal preservation rather than radical orchiectomy.^17,18 Follow-up practices were similarly inconsistent, with surveillance intervals ranging from 6 months to 12 or 13 months depending on the case.^13,14,17 Although paratesticular leiomyosarcoma has been previously documented, the tumor remains exceedingly rare, and the current literature is insufficient to establish an evidence-based standard for management. It is the author’s opinion that reporting this case contributes meaningful data to the collective clinical experience, helping clarify pattern presentations, potential radiologic or pathologic variants, and therapeutic outcomes. Such evidence is essential for eventually guiding stronger consensus recommendations regarding optimal treatment strategies, prognostic factors, and appropriate follow-up intervals.

Conclusion

This case highlights an uncommon presentation of a paratesticular leiomyosarcoma. The patient’s painless scrotal swelling, normal tumor markers, and ultrasound findings guided the initial clinical suspicion, while definitive diagnosis relied on surgical pathology and immunohistochemistry. Complete surgical excision offered effective local control with no evidence of recurrence at 8 months follow-up. Due to the possibility of late recurrences with sarcomas, patients like ours will require long-term follow-up. Given the rarity of this entity, individual case reports contribute valuable insights into diagnosis, management, and prognosis, underscoring the need for ongoing documentation and research in this domain. Despite the grade nature, predisposing factors and diagnostic criteria, literature indicates that prognosis of testicular leiomyosarcoma appears to be better if treated early.