A case report of testicular plasmacytoma misdiagnosed as lymphoma by ultrasound

Abstract

Testicular plasmacytoma is an extremely rare malignant tumour whose clinical manifestations resemble those of common testicular tumours, making preoperative diagnosis challenging. This paper reports a case of a 63-year-old male patient who presented for consultation due to'unintentionally discovering enlargement of the right scrotum for four days’. The ultrasound findings bear a striking resemblance to lymphoma, leading to misdiagnosis as lymphoma on ultrasound. Following radical orchiectomy, pathological and immunohistochemical examination confirmed the diagnosis of plasmacytoma. Although rare, testicular plasmacytoma should be considered as part of the differential diagnosis for testicular masses.

1. Introduction

Plasmacytoma is a monoclonal proliferation originating from plasma cells, most commonly occurring in the bone marrow (multiple myeloma) but also arising in extramedullary soft tissues, where it is termed extramedullary plasmacytoma.¹ The incidence rate is slightly higher in males than in females, with the majority of cases occurring in individuals aged between 40 and 60. Extramedullary plasmacytoma predominantly occurs in the head and neck, gastrointestinal tract, upper respiratory tract, and central nervous system. Primary occurrence in the testis is exceedingly rare, accounting for less than 0.15 % of all testicular malignancies.² Testicular plasmacytoma may present as an isolated primary lesion,³ or manifest as a recurrence or metastatic presentation of systemic multiple myeloma. Owing to the non-specific nature of its clinical manifestations and imaging features, it is frequently misdiagnosed as lymphoma, seminoma, or other germ cell tumours.⁴ This paper reports the ultrasound features of testicular plasmacytoma, aiming to enhance awareness of this condition among urologists and sonographers.

2. Case presentation

A 63-year-old male patient presented to our hospital complaining of ‘accidently discovering enlargement of the right scrotum for four days’. Four days prior, whilst bathing at home, the patient noticed that the right scrotum was markedly larger than the left. There was no redness, swelling, or ulceration, no distinct pain, no significant fever, and no haematuria. The size of the scrotum did not change with altered body position. There were no urinary abnormalities such as frequent urination, urgency, or dysuria. The patient had a history of two stem cell transplants for multiple myeloma. Physical examination revealed no enlarged lymph nodes palpable in the bilateral inguinal regions. The right testis showed increased volume with a palpable firm mass, approximately 5 cm in size, with relatively clear borders and no tenderness. The mass was well-defined from the epididymis and demonstrated a negative transillumination test. No abnormalities were noted in the left testis or epididymis. Laboratory investigations showed that the complete blood count and liver and kidney function tests were all within normal limits. Serum alpha-fetoprotein, human chorionic gonadotropin and other testicular tumour markers were all within normal ranges. Serum protein electrophoresis and immunofixation electrophoresis revealed no evidence of monoclonal immunoglobulin. Scrotal ultrasound examination revealed that the right testicle was enlarged with a rounded contour, measuring approximately 53mm × 32mm. Internal echoes were heterogeneous, with a patchy hypoechoic area visible within, measuring approximately 21mm × 13mm (see Fig. 1a). Colour Doppler flow imaging revealed abundant blood flow signals within and around the lesion (see Fig. 1b). No abnormalities were noted in the left testicle. Given the patient's advanced age, the initial diagnosis was considered to be right testicular lymphoma. Following thorough communication with the patient and the signing of an informed consent form, a radical orchiectomy was performed on the right testicle. Postoperative routine histopathology and immunohistochemical analysis confirmed a right testicular plasmacytoma. In conjunction with the patient's medical history, this was considered an extramedullary recurrence of multiple myeloma. The patient underwent a bone marrow aspiration two weeks after surgery. Pathological findings revealed hyperplasia of granulocyte, erythrocyte, and blast cells, with scattered plasma cells. Immunohistochemistry showed positivity for CD38 and CD138, along with light chain restriction. The diagnosis was plasma cell myeloma. Subsequently, multiple courses of KPD chemotherapy were administered, followed by favorable recovery over the next six months.

Fig. 1.

Testicular colour Doppler ultrasound reveals: a. Enlarged right testicle with a rounded contour, exhibiting heterogeneous internal echoes and patchy hypoechoic areas. b. Colour Doppler flow imaging demonstrates abundant blood flow signals within and around the lesion.

This study was approved by the Ethics Committee of the First Affiliated Hospital of Ningbo University (Approval No. 2021RS058).

3. Discussion

Testicular plasmacytoma is a rare condition, predominantly occurring in the elderly.⁵ Essentially a malignant clonal proliferation of plasma cells occurring within the soft tissues of the testis, classified as an extramedullary plasmacytoma. Some patients may develop monoclonal gammopathy. Its typical manifestation is a painless, firm testicular tumour. As demonstrated in this case, the patient presented with the characteristic finding of painless enlargement of the right testicle, with negative tumour markers. Preoperatively, it proved challenging to differentiate this condition from the more common seminoma or lymphoma.

Ultrasound is the preferred imaging modality for testicular tumours. Testicular plasmacytoma typically presents as a solid mass exhibiting heterogeneous hypoechoic features, indistinct borders, and rich vascularity. Lymphoma and seminoma also manifest as solid masses with heterogeneous hypoechoic characteristics, indistinct borders, and abundant blood flow, rendering differentiation between the three entities challenging.⁶ Therefore, the final diagnosis relies entirely on pathological examination, particularly immunohistochemistry. The characteristic markers of plasmacytoma are CD138 and CD38 positivity, accompanied by light chain restriction, which is key to distinguishing it from lymphoma and other germ cell tumours. Particular vigilance is warranted regarding the development of testicular plasmacytoma in patients with a history of multiple myeloma.⁷

In terms of treatment, radical inguinal orchiectomy is the standard approach for solitary lesions, serving both diagnostic and therapeutic purposes. Whether adjuvant radiotherapy to the scrotal region is required postoperatively remains controversial, with some scholars suggesting radiotherapy may reduce local recurrence rates. Postoperative comprehensive staging investigations are required to rule out multiple myeloma. These include serum protein electrophoresis, immunofixation electrophoresis, and serum free light chain detection to assess M-protein levels. Bone marrow aspiration biopsy is performed to determine the presence of clonal plasma cell infiltration within the marrow. Whole-body imaging studies (such as low-dose CT, PET/CT, or MRI) are employed to evaluate other bone or extramedullary lesions. Should testicular involvement represent an extramedullary manifestation of multiple myeloma, treatment should primarily consist of systemic chemotherapy.^8,9

4. Conclusions

This case demonstrates that although testicular plasmacytoma is exceedingly rare, it should be considered in the differential diagnosis of testicular tumours in elderly patients, particularly those with a history of multiple myeloma. Preoperative diagnosis is challenging, with confirmation relying on postoperative histopathology and immunohistochemistry. Upon confirmation of diagnosis, a comprehensive systemic assessment must be conducted to determine the disease stage, thereby facilitating the development of an optimal clinical treatment plan. Patients should be advised to undergo long-term follow-up.¹⁰

CRediT authorship contribution statement

Danhong Yu: Writing – review & editing, Writing – original draft, Formal analysis, Data curation. Nianyu Xue: Resources, Methodology, Investigation, Conceptualization.

Ethics approval and consent to participate

Authors reporting experiments on humans and/or the use of human tissue samples must confirm that all experiments were performed in accordance with relevant guidelines and regulations. All methods were carried out in accordance with relevant guidelines and regulations. All experimental protocols were approved by Ethics Committee of The First Affiliated Hospital of Ningbo University. This retrospective study was approved by the Ethics Committee of The First Affiliated Hospital of Ningbo University (Reference: 2021RS058). Informed consent was obtained from all subjects and/or their legal guardian(s).

Consent for publication

Not applicable.

Availability of data and materials

All data generated or analysed during this study are included in this published article.

Funding

Not applicable.

Conflict of interest

The authors declare that they have no competing interests.