37 Rare paratesticular fibrous pseudotumour in a pediatric patient presents both diagnostic and treatment challenges

Introduction/Objective Paratesticular fibrous pseudotumors (PFP) are rare pathologies that can be challenging to differentiate from cancerous lesions. They usually arise between the testicular tunica layers and are thought to arise from an inflammatory process. They can have various morphological and topographic characteristics, which add to their diagnostic challenge. The management of these PFPs is challenging as well due to difficulties in diagnosing PFPs preoperatively. Ultimately, many men with PFPs undergo orchiectomies despite the benign nature of the pathology. Below, we present the case of a young male who underwent an orchiectomy after discovering an intraoperative lesion that was later determined to be a PFP. Methods/Case Report A 15-year-old Caucasian male presented with a right complex hydrocele and a small left varicocele both of which had been present for approximately 19 months. The hydrocele and varicocele were visualized via ultrasound of the scrotum and testicles preoperatively and the patient was admitted for a right hydrocelectomy. The ultrasound demonstrated a right testicle measuring 5.4 x 2.6 x 2.1 cm and a left testicle measuring 4.4 x 1.9 x 3 cm. It also noted a complex cystic structure seen within the right scrotal with displacement and poor visualization of epididymis which measured 12.6 x 6.5 x 6.3 cm. The left-sided epididymis appeared normal. There was no left-sided hydrocele, but a left-sided varicocele was noted. Of note, there was no sonographic evidence of an intratesticular mass, testicular torsion, or any other acute abnormality. However, during the procedure, the surgeon noted a solid tumor of the right testicle which had not been picked up by the preoperative ultrasound. Tumor markers, alpha-fetoprotein (AFP), beta human chorionic gonadotropin (beta-HCG), and lactate dehydrogenase (LDH), were drawn during the procedure. These were all within normal limits. The decision was made to proceed with a right radical orchiectomy instead. The right testicle and spermatic cord were sent to pathology. Upon gross examination, there was a 3 cm unilocular cyst containing straw-colored serous fluid adjacent to the spermatic cord. The tunica vaginalis of the testicle was noted to be thickened and immobile with diffuse hemorrhagic adhesions and discolorations. Upon further sectioning, a 3.5 x 0.5 x 2.5 cm well-circumscribed and encapsulated lesion was found under the tunica albuginea. It was red-brown, with cystic cut surfaces and a thickened cyst wall which impinged on but did not invade the testicular parenchyma. Upon microscopic examination, there was variably cellular fibro-collagenous spindle cell proliferation with intermixed densely hyalinized plaque-like features, lymphoplasmacytic infiltrates, and moderately cellular areas with myofibroblastic features containing whorling spindle cells. There was central cavitation of the lesion with granulation tissue and possible infarct-related hemorrhage and necrotic material. The spindle cells stained positive for desmin, smooth muscle actin, and AE1/AE3. Stains were done with calretinin, inhibin, ER, PLAP, ALK1, SALL4, CD30, CD31, CD34, CD117, and WT-1. These were negative. Additional immunostains were performed at an outside facility including myogenin, MyoD1, and ERG which were negative for the tumor cells but there was retained nuclear staining of RB1. The cyst described above as adjacent to the spermatic cord, contained cells lining it that stained positive for AE1/AE3 cytokeratin and calretinin. This was determined to be consistent with a benign mesothelial cyst. Differentials for the lesion included paratesticular fibrous pseudotumor, inflammatory myofibroblastic tumor, leiomyoma, or a regressed germ cell tumor. Based on the histological findings along with the morphological features and immunoprofile, the most likely diagnosis is a paratesticular fibrous pseudotumor. The patient did well post-operatively and did not experience any complications from the surgery. Results NA Conclusion PFPs are rare, particularly in the pediatric population. Despite the increase in case reports, there is still no clear answer on the etiology of PFPs. Additionally, although there are imaging options available like ultrasonography to attempt to visualize the PFP, they are not always reliable. Attempting to avoid unnecessary orchiectomies remains a challenge due to the diagnostic challenge these tumors present.