Primary Retroperitoneal DOG-1 Positive & P16 Negative Squamous Cell Carcinoma in a Male – A Rare Case Report

Case Report

Abstract

Retroperitoneal neoplasms represent a rare subset of tumors, accounting for only 0.1–0.2% of all cancers. Among them, squamous cell carcinoma (SCC) arising in the retroperitoneal cavity is exceedingly rare, with limited understanding of its pathogenesis and clinical features. Here, a case of primary retroperitoneal squamous cell carcinoma is reported in a male patient who presented with complains of abdominal pain and recurrent diarrhea. On radiological imaging, a large, heteroechoic mass with necrotic components enveloping the celiac trunk in the retroperitoneal region was noted. Histopathological assessment of a core biopsy confirmed a malignant tumor with large atypical cells in clusters with moderate to marked nuclear pleomorphism, prominent nucleoli and abundant eosinophilic to clear cytoplasm. An immunohistochemical (IHC) panel, including markers such as Epithelial Membranous Antigen (EMA), PanCK, CK7, CK20, DOG-1, CD117, β-Catenin, SOX10, CD10, SMA, S100, CEA, TTF-1, CDX2, HMB45, p16, p53, p40 and p63 was systematically conducted for further characterization. Based on the Immunohistochemical (IHC) results, a myriad of differentials were ruled out and the diagnosis of primary retroperitoneal squamous cell carcinoma with DOG1 positivity and P16 negativity was established. Based on extensive research conducted on PubMed, Scopus, and Google Scholar, it appears that this case could potentially be the first documented instance of a male patient with primary retroperitoneal squamous cell carcinoma exhibiting positive DOG1 and negative p16.