Teaching Case

A 68-year-old male presented with a painless mass on the shaft of the penis. Physical examination revealed a firm, nodular lesion. After a core-biopsy with characteristics compatible with fusocellular undifferentiated subtype of sarcoma of the corpus cavernosum of the penis, and proper imaging staging, the patient underwent surgical excision followed by adjuvant chemoradiotherapy.

MRI demonstrated a large mass measuring 8 cm in the penile shaft, predominantly intermediate in signal intensity on T2-weighted sequences and showing avid enhancement after intravenous contrast administration (Figures 1a, 1c and 1d). Heterogeneous areas suggestive of necrosis and haemorrhage were present, along with marked diffusion restriction (Figures 1b and 1c). The tumour invaded a significant portion of the corpora cavernosa, disrupting the tunica albuginea, Buck's fascia, and septum (Figure 1a). No urethral invasion was noted (later confirmed by urethroscopy). No suspicious lymph nodes were identified. Full-body CT showed the penile lesion with heterogenous enhancement but no evidence of distant lesions (Figures 2a and 2b).

Background

Undifferentiated fusocellular sarcoma (UFS) is a rare malignant tumour characterized by spindle-shaped cells lacking specific differentiation. Sarcoma of the corpora cavernosum of the penis is an extremely rare entity, with only a few reported cases in the literature.

UFS is a challenging diagnosis due to its rarity and lack of specific clinical features. It typically arises from the mesenchymal cells of the corpus cavernosum, which are responsible for maintaining the structural integrity and erectile function of the penis. It is an aggressive tumour due to a lack of differentiation.

Clinical Perspective

Patients with UFS of the penis often present with a painless mass or swelling on the shaft of the penis. However, these symptoms are nonspecific and can mimic other benign conditions, leading to diagnostic challenges. Therefore, it is crucial to consider this rare malignancy in the differential diagnosis of penile masses, especially in older individuals. Imaging plays a pivotal role in evaluating the local extent of the tumor, potential invasion into adjacent structures, and guiding appropriate management decisions.

Imaging Perspective

Pelvic MRI provides detailed anatomical information and helps determine the extent of the tumour. It also allows for further characterization of the presence of necrosis, haemorrhage, and areas with diffusion restriction. Ultrasound is useful in guiding biopsy and, in this case, showed a heterogeneous hypoechoic lesion. CT is helpful to rule out the presence of distant metastases, providing valuable information for treatment planning.

Outcome

Following a multidisciplinary discussion, the patient underwent total penectomy and perineal urethrostomy as the recommended therapeutic options. Imaging played a vital role in determining the proximal extent of the tumour and local staging, enabling the surgical procedure. However, despite the initial treatment, the patient experienced a recurrence of the tumour after four years, which demonstrated aggressive disease progression. Unfortunately, this ultimately led to the patient's demise.

Take Home Message / Teaching Points

UFS of the penis is an exceptionally rare malignancy that requires early diagnosis and aggressive surgical intervention. Imaging, particularly pelvic MRI, plays a crucial role in assessing the local extent of the tumour and guiding appropriate management decisions. The diagnostic clues, including signal intensity patterns, contrast enhancement, presence of necrosis and haemorrhage, diffusion restriction, and invasion into adjacent structures, help differentiate this malignant tumour from benign conditions. However, due to the aggressive nature of this sarcoma, close surveillance and timely intervention are essential for improved outcomes.