A Case Report of Surgical Resection of Primary Retroperitoneal Squamous Cell Carcinoma and Postoperative Local Recurrence.

A 55-year-old female patient, with a history of endometriosis in her 30s, hypertension, and cervical lymph node tuberculosis, initially presented with mild abdominal pain and fever. Although her symptoms improved naturally, computed tomography (CT) revealed a large mass (5 × 4 × 7.5 cm) located in the retroperitoneal cavity of her right lower abdomen, compressing the inferior vena cava (IVC) and abdominal aorta (Figures  1A - 1B ). Laboratory findings showed an interleukin-2 receptor level of 835 U/mL (reference range, 122-496), and the carbohydrate antigen 125 level was 103.7 U/mL (reference range, 0-35). Other tumor markers, including carcinoembryonic antigen, carbohydrate antigen 19-9, and duodenal pancreatic cancer antigen 2, were within normal limits. Serum SCC antigen levels measured postoperatively were within the normal range. In addition, urinary metanephrine and normetanephrine levels were within normal limits. Preoperative and postoperative laboratory findings are summarized in Table 1 . (A) Axial view of CT showed a 5 × 4 × 7.5 cm iso-density mass in the right retroperitoneum (arrowheads). (B) On 3D reconstruction images of CT, the Ao and IVC are compressed by the tumor. Ao: aorta, IVC: inferior vena cava, LCIA: left common iliac artery, RCIA: right common iliac artery Reference ranges for urinary metanephrine and normetanephrine are not established for spot urine samples. ALT: alanine aminotransferase, AST: serum aspartate aminotransferase, BUN: blood urea nitrogen, CA125: carbohydrate antigen 125, CA19-9: carbohydrate antigen 19-9, CEA: carcinoembryonic antigen, Cl: chlorine, CRP: C-reactive protein, DUPAN2: duodenal pancreatic cancer antigen 2, HCT: hematocrit, HGB: hemoglobin, HPV: human papilloma virus, IL-2 receptor: interleukin-2 receptor, K: potassium, Na: sodium, PCT: procalcitonin, RBC: red blood cell, SCC: squamous cell carcinoma, WBC: white blood cell Esophagogastroduodenoscopy and total colonoscopy revealed no abnormalities. Positron emission tomography (PET) revealed a mass with a maximum standardized uptake value (SUV) of 21 (Figure  2A ). Magnetic resonance imaging revealed an isointense signal on T2-weighted images and a high signal on diffusion-weighted images (Figures  2B - 2C ). Based on these findings, the differential diagnoses were neurogenic tumors, paraganglioma, malignant lymphoma, and Castleman disease. However, because a definitive diagnosis could not be established through this comprehensive preoperative workup alone, a clinical decision was made to proceed with laparotomy. The primary objective was to obtain a histological diagnosis via excisional biopsy and, if feasible, perform a complete therapeutic resection. (A) PET showed the mass with a maximum standardized uptake value of 21 (arrowheads). (B) MRI showed an isointense signal on T2-weighted images (arrowheads). (C) MRI showed high signal on the diffusion-weighted image (arrowheads). The primary surgery revealed that the mass was located in the retroperitoneal space and was pushing the right ureter ventrally. It adhered to the right ureter, IVC, and right common iliac artery but did not invade. Therefore, the mass was completely removed without damaging other organs (Figure  3 ). The operative time was 262 minutes, and the intraoperative blood loss was 58 mL. The postoperative course was uneventful, and the patient was discharged on postoperative day 6. Histopathological examination suggested epithelial malignancy with SCC. Immunostaining was positive for p40 and p16 but negative for nuclear protein in the testis. Ki-67 expression was 58% (Figures  4A - 4D ). Diffuse positivity for p16 suggested that the primary organs were the middle pharynx or cervix. A portion of the vascular sheath of the right common iliac artery was resected en bloc because of the severe adhesion (arrowheads). Ao: aorta, IVC: inferior vena cava, RCIA: right common iliac artery (A) The tumor was an 8 × 7.5 × 4 cm firm and elastic mass, covered with a fibrous capsule. (B) Histopathological examination revealed an epithelial malignant tumor. (C, D) Immunohistochemical analysis showed positivity for p16 and p40, respectively. Given the pathological findings, further evaluations were conducted by the otolaryngology and gynecology departments to identify the primary tumor; however, no abnormalities were detected in the pharynx, uterus, or adnexa. Serum HPV DNA test results were negative. Therefore, we diagnosed SCC of primary retroperitoneal origin. As there were no signs of residual carcinoma based on the radiological and intraoperative findings, the patient was followed up without any additional treatment. Seven months after surgery, follow-up CT showed a small mass (1.3 × 0.8 cm) in the aortocaval area near the site where the primary tumor was located. PET showed a mass with a maximum SUV of 6.7 and no evidence of distant metastasis (Figures  5A - 5B ). Local recurrence was determined, and surgical treatment was performed. The tumor was identified on the lumbar vertebrae between the abdominal aorta and IVC after mobilizing the duodenum. It adhered to the aorta and IVC but was completely resected without damage to other organs. The operative time was 189 minutes, and the intraoperative blood loss was 150 mL. The postoperative course was uneventful, and the patient was discharged on postoperative day 6. (A) PET revealed a small mass (1.3 × 0.8 cm) with a maximum standardized uptake value of 6.7 (arrowheads). (B) On 3D-CT reconstructed imaging, the tumor was located in the para-aortic region near the previous surgical site (dotted line). Ao: aorta; Du: duodenum; IVC: inferior vena cava Histopathological findings showed that the tumor cell type was SCC, which is consistent with local recurrence of primary retroperitoneal SCC. Because there were no signs of distant metastasis, additional treatment was not performed after careful discussion with the patient. The patient has remained in good condition, with no recurrence for over four years after the second operation.

Retroperitoneal tumors are rare neoplasms accounting for only 0.2% of all tumors [ 1 ]. While most cases arise from soft tissue, epithelial tumors of primary retroperitoneal origin have rarely been reported [ 2 ]. When squamous cell carcinoma (SCC) occurs in the retroperitoneum, key considerations include determining whether it is primary or metastatic, and if primary, identifying the type of cells that serve as the site of origin. Although the etiology of primary retroperitoneal SCC remains unclear, hypotheses include squamous metaplasia of embryonic rests, human papillomavirus (HPV) infection, and malignant transformation of endometriosis [ 2 - 4 ]. Complete surgical resection is currently considered the cornerstone of treatment; however, standardized management strategies are lacking, and there is a significant gap in evidence regarding the treatment of local recurrence [ 3 , 5 , 6 ]. In this report, we present a patient with primary retroperitoneal SCC who underwent surgical resection of the primary tumor and local recurrence.

The retroperitoneum originates from the mesoderm, and retroperitoneal tumors are predominantly non-epithelial, with epithelial tumors being relatively rare. The origin and etiology of retroperitoneal SCC remain unknown. Additionally, some reports suggest the involvement of HPV in retroperitoneal SCC [ 5 , 6 ], whereas others indicate the possibility of developing SCC based on endometriosis [ 4 ]. In the pathological examination of this case, only pure SCC components were observed, with no evidence of endometriosis. Furthermore, no abnormalities were detected in the peritoneal cavity, uterus, or adnexa, effectively ruling out the possibility of tumor development from endometriosis or metastasis from gynecological cancer. Comprehensive systemic evaluation failed to identify the primary lesion, leading to the diagnosis of primary retroperitoneal SCC. Immunohistochemical analysis revealed positive staining for p16; however, HPV was less likely to be involved in this tumor because of a negative HPV DNA test. Previous studies have revealed several cases of SCC that were considered to be retroperitoneal in origin, as summarized in Table  2  [ 2 - 11 ]. The most common age was approximately 50 years, and most patients were female. Half of the patients were diagnosed using CT or ultrasound-guided biopsy, and the other half underwent exploratory laparotomy before confirming the diagnosis. Curative surgery was performed in nine patients, with postoperative therapy (chemotherapy, radiation, or concomitant chemoradiotherapy) administered in most of them. Among the patients who underwent curative resection, three experienced recurrence, two local recurrences, and one supraclavicular lymph node recurrence. One patient with local recurrence was treated with chemotherapy (taxane and platinum), whereas another patient did not undergo further treatment and died six months after surgery. AWD: alive with disease; CRT: chemoradiotherapy; CT: chemotherapy; DOD: dead of disease; NED: no evidence of disease Among the five patients who did not undergo surgical resection, one remained well with no evidence of relapse following chemoradiation with cisplatin. Of the remaining four patients, two received chemoradiation therapy (paclitaxel and carboplatin or cisplatin combined with radiotherapy) and died within one year after the initial diagnosis; the other two patients were undergoing ongoing treatment at the time of analysis. One patient did not undergo any form of therapy and died one year after the initial diagnosis. In the present case, recurrence was observed seven months after the initial surgery. Based on preoperative imaging, which suggested that the recurrent lesion was isolated and technically resectable, a clinical decision was made to prioritize a second surgical intervention. Complete gross resection was achieved during reoperation. Complete resection likely contributed to a better prognosis and no recurrence in the following four years. Given the lack of sufficient evidence supporting adjuvant therapy, no additional postoperative treatments were administered. These findings suggest that surgical resection is effective in cases of oligo-recurrence in which complete resection is possible. To the best of our knowledge, this is the first case report describing the successful treatment of retroperitoneal SCC and its local recurrence through surgical resection, achieving long-term survival. A surgical treatment strategy aimed at achieving a “cancer-free” status through reoperation may contribute to improved long-term prognosis.

We report a case of retroperitoneal SCC of unknown primary origin. Surgical treatment is effective for resectable retroperitoneal SCC, even in cases of local recurrence. Although the findings presented here are based on clinical observations from a single case, our experience demonstrates that complete surgical resection can achieve long-term, disease-free survival, even in the setting of local recurrence. Given the rarity of this disease, further studies are warranted to optimize management strategies and refine patient selection for surgical treatment.