An Isolated Penile Mass in a Young Adult Turned Out To Be a Primary Marginal Zone Lymphoma of the Penis. A Case Report and a Review of Literature

Case Report

A 24-year-old Asian man presented in April 2012 to our Andrology Unit with a painless and mobile nodule localized in the ventral part of the proximal shaft of the penis, measuring 1 cm in its major diameter. On physical examination, testicular (12 of Prader) and inguinal lymph nodes were normal; no superficial lymphadenopathies were documented, nor any hepatosplenomegaly. The patient was totally asymptomatic, no general symptoms of lymphoma, such as fever, night sweats, weight loss or itching were reported. Moreover, the patient did not complain of difficulty in urination, priapism or urethral bleeding.

The nodular lesion was firstly evaluated through Doppler ultrasonography, which showed a hypoechoic and highly vascularized solid mass of 13×6 mm in diameter involving the distal part of the shaft of the penis, localized in the corpus spongiosum of the urethra and causing urethral compression; the lesion also protruded externally in the subcutaneous layer of the penis. Subsequent magnetic resonance imagine (MRI) of the penis, performed after the injection of 5 μg of prostaglandin-E¹ in the corpora cavenosa, confirmed the size and the position of the lesion, which appeared to be cleaved from the corpus spongiosum of the urethra after contrast infusion, however, determining a dislocation of the urethral canal (Figure 1, A). Findings were similar to those previously reported elsewhere (15).

One month later, the patient underwent surgical excision of the mass: a circular mucosal incision distant 1 cm from the glans penis was performed, with subsequent penile degloving; after a bilateral incision of Buck's fascia, the lesion was found to be in close contact with the ventral part of the distal urethra (Figure 1, panel B). The lesion was excised; it appeared completely capsulated and friable, and it did not seem to incorporate the corpus spongiosum, not to be adherent to the cavernous bodies (Figure 1, C and D). Upon histological examination, a diffuse proliferation of small CD20-positive lymphocytes was described, along with accompanying monotypic plasma cells expressing immunoglobulin λ light chain. The diagnosis was consistent with extranodal marginal zone B-cell non-Hodgkin's lymphoma, MALT-type (Figure 2). Evidence of re-arrangement of the immunoglobulin light chain genes was a proof of clonality of the lymphoproliferative process.

In order to accomplish accurate disease staging, a computed tomographic scan of the chest, abdomen and pelvis was performed, showing no lymph node enlargement at mediastinal or retroperitoneal sites. A bone marrow trephine biopsy showed no evidence of disease infiltration. All the criteria for the diagnosis of primary – i.e. stage I_E A according to the Ann Arbor staging system (16) – MALT lymphoma were fulfilled.

The patient's complete blood counts and blood chemistry were all within normal ranges; serum immunoglobulin concentrations and free light chain κ/λ ratio were normal; no monoclonal components were documented on serum immunofixation. Serological tests for hepatitis B and C virus and human immunodeficiency virus were all negative; neither IgG nor IgM antibodies directed to Treponema pallidum were detected on immunoblot.

The patient underwent a consolidative immunotherapy with the anti-CD20 monoclonal antibody rituximab, which was administered once a week for four consecutive weeks at a dose of 375 mg/m². The treatment was perfectly tolerated, with no remarkable side-effects.

Disease re-staging was performed two months after the last rituximab administration through a penile MRI: neither residual neoplastic masses were detected, nor any recently developed focal lesions of the corpora carvernosa and corpus spongiosum. Inguinal lymph nodes were not enlarged. The penile shaft showed no pathological incurvation while erected.