Superficial Penile Leiomyosarcoma Mimicking a Benign Tumor.

Sir,

Primary penile sarcoma is extremely rare, with an incidence of 0.6–1.0 per 100,000 individuals.[1] Leiomyosarcoma is the second most common primary penile sarcoma with two major subtypes: superficial type, which occurs in the superficial smooth muscle layer and progresses slowly; and deep type, which occurs in the deep smooth muscle layer of the corpus cavernosum, has a poor prognosis, and is treated using a wide local resection.[12] Patients with superficial penile leiomyosarcoma often present with painless subcutaneous benign-appearing tumors.

We report a case of superficial penile leiomyosarcoma wherein ultrasonographic findings helped distinguish a malignant lesion from a benign one. A 31-year-old man was diagnosed with a subcutaneous penile tumor 7 years ago. Recently, rich vascularity was detected on ultrasonography, despite suspicion of a benign tumor, he was subjected to a biopsy evaluation. The patient was referred to our hospital due to inconclusive pathological findings. Physical examination revealed an elastic, subcutaneous mass (1.7 × 1.1 cm2), with good mobility, over the penile dorsum on the right side [Figure 1]. Ultrasonography revealed a hyperechoic, well-defined oval mass [Figure 2a], and color Doppler mode displayed multidirectional blood-flow signals entering the tumor [Figure 2b], leading to initial suspicion of atheroma.

Figure 1

Clinical findings: a 1.7 × 1.1 cm2 subcutaneous mass on the dorsal surface of the right side of the penis

Figure 2

(a) Ultrasonographic findings: hyperechoic, well-defined oval mass (b) Ultrasonographic findings in color Doppler mode: multidirectional dendritic blood-flow signals entering tumor

The tumor was easily removed using local excision, with no adhesion to other structures. The specimen appeared as a grayish, smooth, well-defined mass. Histopathological analysis revealed a well-defined subcutaneous tumor composed of spindle-shaped cells [Figure 3a]. These tumor cells showed atypical nuclei proliferated in interlacing fascicles [Figure 3b]. Immunohistochemistry revealed tumor cell positivity for α-smooth muscle actin [Figure 3c], desmin, h-caldesmon, and androgen receptor [Figure 3d]; and the Ki-67 index was 5%. Therefore, the tumor was diagnosed as a superficial penile leiomyosarcoma. The patient was complication- and recurrence-free at the 14-month follow-up.

Figure 3

(a) Hematoxylin-eosin staining (×100): well-defined subcutaneous tumor composed of spindle-shaped cells with many blood vessels. (b) Hematoxylin-eosin staining (×200): proliferative spindle-shaped tumor cells in interlacing fascicles (c) Immunohistochemical staining (×400): tumor cells positive for α-smooth muscle actin. (d) Immunohistochemical staining (×400): tumor cells positive for androgen receptors

Thirty-four patients (n = 7, glans; n = 27, prepuce and shaft) including the current one, with superficial penile leiomyosarcoma, have been reported in the literature. Occasionally, leiomyosarcoma presents as a lobulated, firm, reddish mass in the glans.[3] Whereas, in the prepuce and shaft, it presents as a subcutaneous tumor with good mobility, comparable to that of atheroma, leiomyoma, and schwannoma. Here, an ultrasound revealed intratumoral blood flow. Vascularity between a benign and malignant lesion can also be distinguished in uterine leiomyosarcoma and could be a determining factor for suspected malignant tumors.[4]

Out of the reported patients, 29 underwent initial local excision, 4 underwent partial amputation, and radiation was administered to only 1 patient. The recurrence rate with amputation and local excision was 0% and 17.2% (0/4 cases vs. 5/29 cases; mean duration to recurrence: 11.6 years), respectively. Recurrence was also reported in the patient treated with radiotherapy. No recurrence was observed after a repeat resection.

Superficial penile leiomyosarcoma manifests clinical features typical of benign skin tumors. Ultrasonography is useful to distinguish this cancer from benign skin tumors. Findings of color Doppler ultrasonography facilitated accurate diagnosis and treatment in our patient. Thus, ultrasonography and histopathological examination are essential to prevent misdiagnosis of malignancy in clinically benign-appearing tumors.

Financial support and sponsorship

This study was financially supported in part by the National Cancer Center Research and Development Fund (2020-J-3).

Conflicts of interest

There are no conflicts of interest.