包皮發炎性肌纖維母細胞腫瘤:案例報告

張哲睿¹、陳生文¹、張彰琦¹、邱逸淳^1,2,3,4

¹臺北市立聯合醫院忠孝院區外科部泌尿科; ²國立陽明交通大學醫學院醫學系泌尿學科; ³國立陽明交通大學書田泌尿研究中心; ⁴台北大學運動健康科學系

Inflammatory myofibroblastic tumors of prepuce: a case report

Che-Jui Chang¹, Sheng-Wen Chen¹, Chang-Chi Chang¹, Yi-Chun Chiu^1,2,3,4

¹ Division of Urology, Department of Surgery, Taipei City Hospital, Zhongxiao Branch, Taipei, Taiwan.

² Department of Urology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan.

³ Shu-Tien Urological Research Center, National Yang Ming Chiao Tung University, Taipei, Taiwan.

⁴ Department of Exercise and Health Sciences, University of Taipei, Taipei, Taiwan.

Introduction:

Inflammatory myofibroblastic tumors (IMTs) are an uncommon myofibroblastic neoplasm with intermediate biological potential, typically found predominantly in children and young adults, showing a slight female preponderance.¹ IMT can occur in various organs throughout the body. First described in the lungs, and also have been found in numerous other anatomical sites, including the abdomen, pelvis, soft tissues, and rarely in bone. Here, we presented a case of IMT of prepuce.

Case presentation:

A 19-year-old Taiwanese man presented to urology outpatient department (OPD) with a mass lesion of prepuce for 2 months. There was no history of fever, gross hematuria, dysuria, urgency, increased frequency of urine, flank pain, poor appetite, night sweats, body weight loss. He had past history of asthma and denied any oncological history. He was a non-smoker and not worked in a place where chemicals or radiation exposed. His family history was negative for any oncological condition. Physical examination showed a movable mass over prepuce with tenderness while pushing (Fig. 1). Sonography of the mass showed increased blood vessel supply (Fig. 2). Wide local excision was performed. Gross examination revealed the specimen is white and elastic, measuring 2.8 x 1.5 x 1.2 cm. Microscopic examination revealed inflammatory myofibroblastic tumor. The well circumscribed tumor composed of the proliferative neoplastic spindle cells, admixed with lymphocytes, arranged in short fascicular and vaguely storiform patterns. The intervening vasculature with focal congestion is evident. Significant nuclear atypia is absent. Mitotic figures are measured up to 7/10 High-power field. The tumor cells extend to the peripheral surgical margin of the specimen. Immunohistochemically, the tumor cells showed diffuse and strong cytoplasmic immunopositivity for ALK1. The other immunohistochemical studies of the tumor cells showed SMA (+, nuclear staining), CD117 (-), CD34 (-), S100 (-) and FACTOR XIIIA (+). Computed tomography (CT) had not been done yet.

Discussion:

IMTs present a diagnostic challenge due to their diverse clinical manifestations and histological mimicry of other neoplastic and inflammatory processes. These tumors often manifest nonspecific symptoms related to their anatomical location and size, such as pain, mass effect, obstructive symptoms, or constitutional symptoms like fever and weight loss. Radiologically, IMTs can appear as well-defined solitary masses with variable enhancement on CT or magnetic resonance imaging (MRI), but these imaging features lack specificity and overlap with other benign and malignant entities. Therefore, definitive diagnosis usually requires histopathological examination of tissue obtained through biopsy or surgical resection.²

Histologically, IMTs typically exhibit a proliferation of spindle-shaped myofibroblastic cells arranged in a storiform or fascicular pattern, accompanied by a mixed inflammatory infiltrate rich in plasma cells, lymphocytes, and eosinophils. Immunohistochemical staining is crucial for confirming the diagnosis, with characteristic positivity for markers such as smooth muscle actin (SMA). The tumors display no reactivity to S-100 protein (S-100), myogenin, cluster of differentiation 117 (CD117), and epithelial membrane antigen (EMA), while staining for cytokeratin (CK) AE1/3 can be focally positive. All IMTs show wildtype p53 expression. Anaplastic lymphoma kinase (ALK) gene translocation can be detected in 50–60% of IMTs. The most frequent fusion partners are cysteinyl-tRNA synthetase (CARS) gene, clathrin heavy chain (CLTC) gene, RAN-binding protein 2 (RANBP2) gene, 5-aminoimidazole-4-carboxamide ribonucleotide transformylase (ATIC) gene, SEC31 homolog A (SEC31A) gene, tropomyosin 3 (TPM3) gene, tropomyosin 4 (TPM4) gene, fibronectin 1 (FN1) gene, protein kinase CAMP-dependent type I regulatory subunit alpha (PRKAR1A) gene, EMAP like 4 (EML4) gene, thrombospondin 1 (THBS1) gene, insulin-like growth factor binding protein 5 (IGFBP5) gene, desmin (DES) gene, and tissue inhibitor of metalloproteinase 3 (TIMP3) gene.²

Although considered benign in nature, IMTs can exhibit locally aggressive behavior, with high recurrence rate after excision and exhibit low metastatic potential. The rates of recurrence inside or outside of the lungs have been reported to be 2% and 25%, respectively, while the incidence of distant metastasis has been reported to be less than 5%.³ Management of IMTs typically involves surgical excision with clear margins whenever feasible, although adjuvant therapies such as anti-inflammatory medications, corticosteroids, chemotherapy, targeted therapy, or immunotherapy may be considered in cases of unresectable or recurrent disease.^2,4

Conclusion:

IMTs represent a rare but clinically significant entity with diverse clinical and histological presentations. While typically benign, these tumors can exhibit locally aggressive behavior and have the potential for recurrence or metastasis. Multidisciplinary collaboration among clinicians, radiologists, pathologists, and oncologists is essential for accurate diagnosis, optimal management, and long-term surveillance of patients with IMTs. Further research is needed to elucidate the underlying molecular mechanisms driving IMT pathogenesis and to develop targeted therapeutic strategies for patients with advanced or refractory disease.