Penile metastasis from rectal carcinoma misdiagnosed as Peyronie’s disease: a rare presentation

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer related mortality globally. Metastases typically affect liver, lungs, peritoneum, and lymph nodes. Treatment is based on staging and include chemotherapy, radiotherapy, immunotherapy, or surgery.1 Penis metastasis from CRC is extremely rare occurrence, with limited number of cases documented. Despite its rarity, the presence of penile metastasis signifies advanced disease and poses diagnostic and management challenges. We report the case of a 77-year-old male who presented to our department in November 2024 with a firm, focal, non-ulcerated lesion on the dorsal aspect of the penis, located at the mid-distal third of the shaft. The patient reported having noticed the lesion ⁓1 year earlier and described it as a superficial nodule that had remained stable over time and associated with discomfort during sexual intercourse, although he denied any pain or significant curvature. On physical examination, the lesion appeared as a palpable hard lump, raising suspicion of Peyronie’s disease (PD). The patient’s medical history included hypertension, type 2 diabetes mellitus managed with oral hypoglycemics, hypercholesterolemia, and smoking. In 2021 he was diagnosed with rectal adenocarcinoma (cT2 N0), treated with neoadjuvant chemoradiotherapy followed by transrectal resection. In May 2022, the patient developed liver metastases and subsequently treated with adjuvant chemotherapy and immunotherapy (5-Fluorouracil and Bevacizumab) without significant radiographic improvement. Given his history and differences from typical presentation of PD (pain, curvature), a magnetic resonance imaging (MRI) scan of the penis and pelvis was performed preoperatively to better characterize the lesion. Imaging revealed a swollen appearance of the mid-distal segment of the left corpus cavernosum. Within this area, an altered signal was observed, characterized by moderate hypointensity on T2-weighted sequences, diffusion restriction, and peripheral contrast enhancement, with the lesion measuring 26 × 18 mm. The tunica albuginea at this site was disrupted, and the dartos layer was poorly visualized. The right corpus cavernosum appeared normal (Supplementary Figures S1 and S2). Given the uncertain nature of the mass, the patient was thoroughly counseled preoperatively, he signed an informed consent for surgical exploration with possibility of frozen section and different surgical strategies according to intra-operative findings. Under general anesthesia, a ventral incision was made on the penile skin, followed by dissection through the fascial layers to access the surgical site. On the mid-distal segment of the dorsal surface of the penis, a hard lump mass ⁓3 cm in diameter was identified. This lesion was located at the level of the tunica albuginea and extended into the corpora cavernosa. Biopsy samples from the tunica albuginea and cavernous tissue were sent for intraoperative frozen section analysis. Histopathological exam revealed adenocarcinoma of possible intestinal origin, a partial penectomy was thus performed. Final pathology confirmed the diagnosis of colorectal adenocarcinoma (Supplementary Figure S3). No other signs of metastasis were evident at the subsequent Computed tomography (CT) scan. Epidemiological data about PD are scarce, the prevalence may range from 0.4% to 20.3%, even if often underdiagnosed, a higher prevalence in patients with erectile dysfunction and diabetes is reported. Median age of onset is ⁓50-60 years. The diagnosis is often clinical and supported by medical and sexual history. Physical examination and photographic assessment are often key for a proper diagnosis. Penile doppler ultrasonography after intracavernous phosphodiesterase type 5 inhibitor injection could provide further details on curvature and lesion’s features. Surgery is typically reserved for stable disease for at least 6-12 months. According to European Society for Sexual Medicine (ESSM), surgical treatment should only be performed when the curvature and/or penile deformity and/or inadequate quality of erections do not allow satisfactory sexual intercourse or when the deformity causes severe bother.2 CT and MRI have a limited role in the diagnosis of the curvature and are not recommended on a routine basis; however, MRI scan was recommended in the current case given the uncertain nature of the lesion in a patient with prior rectal carcinoma. Details of clinical presentation may help to distinguish between PD and a metastatic onset. PD usually presents with palpable fibrous plaques along the tunica albuginea, penile curvature, pain during erection, and/or erectile dysfunction. These symptoms tend to be progressive and can significantly affect sexual function. While both PD and penile metastases may present as palpable lesions, their features differ. PD typically manifests as a localized firm plaque on the dorsal shaft with associated curvature and pain.2 Penile metastases often present as diffuse, indurated, or nodular masses without curvature but sometimes with priapism, pain, or urinary symptoms such as dysuria, hematuria, or obstructive voiding complaints, which are typically absent in PD.3 In the current case, the penile induration was initially misleading, however, a metastatic origin was suspected, and the patient was counseled for a different treatment option. Early recognition of penile metastasis is critical as it alters treatment and prognosis. MRI and other imaging modalities aid in differentiating benign from malignant lesions. According to the literature, metastatic colorectal adenocarcinoma to the penis is an exceedingly rare phenomenon, with ˂80 cases reported. More broadly, penile metastases from all primary cancers are very uncommon, with only ⁓300 cases documented in the literature.4 Clinically, penile metastases from CRC often present with nodules, masses, or induration of the penile tissue. Additional symptoms may include ulcerations, priapism, urinary disturbances, or localized pain in the penis or perineum.3 Other primary malignancies known to spread to the penis include prostate cancer, bladder (urothelial) carcinoma, renal cell carcinoma, and lung cancer.4 Awareness of these potential origins is crucial when evaluating atypical penile lesions in oncologic patients. Data from published series indicate that ⁓75% of penile metastases originate from pelvic malignancies. Among these, bladder cancer accounts for 34.7% of cases, followed by prostate cancer (29.8%), CRC (15.7%), and renal cell carcinoma (6.5%).4 The mechanism of penile metastatic spread remains unclear. Despite the rich vascular supply and anatomical proximity to pelvic malignancies, penile metastasis is exceptionally rare. Proposed spread pathways include direct extension, retrograde venous or lymphatic transport, secondary embolism from lung or liver metastases, as well as tumor cell seeding during medical procedures. Among these, retrograde venous transport is considered the primary metastatic spread mechanism.3 In our case, we believe that retrograde venous transport is the most likely route, given the patient’s colorectal adenocarcinoma with liver metastasis. Unfortunately, penile metastases are often associated with poor prognosis, as they typically occur in the context of widely disseminated disease. Treatment options include local excision, total penectomy, chemotherapy, radiotherapy, or in some cases, palliative care, as for today, no national or international guidelines for diagnosis, treatment, and management of penile metastases were suggested. Or Schubert (Conceptualization [equal], Investigation [equal], Writing—original draft [equal]), Maria Chiara Sighinolfi (Conceptualization [equal], Project administration [equal], Supervision [equal]), Francesco Pierconti (Formal analysis [equal]), Gaetano Gulino (Conceptualization [equal]), Pierluigi Russo (Data curation [equal], Investigation [equal]), and Antonio Silvestri (Data curation [equal]), Bernardo Rocco (Supervision [equal]) No specific funding was received for this study. The authors declare no conflict of interest.

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