González Luna Antonio de Jesús, Cuevas Calla Cristina Vanessa, Castrejón Cardona Christian Daniel, Sánchez García José Alejandro, Hernández Ibarra Ricardo
Department of General Surgery, Regional Hospital "Dr. Valentin Gomez Farias", Institute of Security and Social Services for the State Workers (ISSSTE), Zapopan, MEX.
Department of General Surgery, Autonomous University of Guadalajara, Zapopan, MEX.
Cureus. 2025 Jul 3;17(7):e87235. doi: 10.7759/cureus.87235. eCollection 2025 Jul.
This case describes a malignant peripheral nerve sheath tumor (MPNST) arising in the ischiorectal fossa, an anatomical location that is infrequently reported in the scientific literature. The report provides new anatomical and clinical insights into a rare and aggressive neoplasm that is frequently misdiagnosed due to nonspecific symptoms and overlapping histopathological features with other rectal or perianal tumors. A 52-year-old woman with no significant medical or oncologic history presented with mild rectal bleeding and a painful perianal mass, initially presumed to be thrombosed hemorrhoids. Physical examination revealed a tender, erythematous anal region with prolapsed tissue and persistent bleeding. She underwent a Ferguson hemorrhoidectomy and examination under anesthesia as the initial surgical approach. Intraoperatively, a friable exophytic lesion was identified 4 cm from the anal verge, occupying approximately 70% of the rectal lumen. Biopsies initially suggested a well-differentiated squamous carcinoma with sarcomatoid features. Further imaging and histopathological evaluation led to an abdominoperineal resection with hysterectomy due to vaginal invasion. Final pathology revealed a high-grade spindle cell neoplasm with lymphovascular and perineural invasion. Immunohistochemistry showed focal S100 positivity (in an irregular pattern) and negativity for AE1/AE3, HMB45, smooth muscle actin (SMA), and CD117. Although SOX10 immunostaining and molecular testing were not performed due to institutional limitations and lack of access to advanced diagnostic resources, the diagnosis of MPNST was supported by compatible histological features and a broad immunohistochemical panel, including markers such as BCL2, CD34, CDX2, P63, CK7, and CK20, and a pan melanoma panel. This combination of findings effectively ruled out major differential diagnoses such as sarcomatoid carcinoma, melanoma, and gastrointestinal stromal tumors (GIST), supporting the final diagnosis of MPNST. The patient recovered uneventfully from surgery. This case illustrates the diagnostic complexity of MPNST in atypical anorectal locations and emphasizes the need for thorough histopathological and immunohistochemical assessment. Early recognition and complete surgical excision are crucial for improving prognosis in such rare presentations. The limitations related to unavailable molecular testing were acknowledged in the discussion section.
本病例描述了一例发生于坐骨直肠窝的恶性外周神经鞘瘤（MPNST），坐骨直肠窝这一解剖部位在科学文献中鲜有报道。该报告为一种罕见且侵袭性强的肿瘤提供了新的解剖学和临床见解，这种肿瘤常因非特异性症状以及与其他直肠或肛周肿瘤重叠的组织病理学特征而被误诊。一名52岁女性，无重大内科或肿瘤病史，出现轻度直肠出血和肛周疼痛性肿块，最初被认为是血栓性痔疮。体格检查发现肛门区域压痛、红斑，有脱垂组织且持续出血。她接受了弗格森痔切除术及麻醉下检查作为初始手术方式。术中，在距肛缘4 cm处发现一个易碎的外生性病变，占据直肠腔约70%。活检最初提示为具有肉瘤样特征的高分化鳞状癌。进一步的影像学和组织病理学评估导致因阴道侵犯而行腹会阴联合切除术及子宫切除术。最终病理显示为高级别梭形细胞瘤，伴有淋巴管和神经周围侵犯。免疫组化显示局灶性S100阳性（呈不规则模式），AE1/AE3、HMB45、平滑肌肌动蛋白（SMA）和CD117阴性。尽管由于机构限制和缺乏先进诊断资源未进行SOX10免疫染色和分子检测，但MPNST的诊断得到了相符的组织学特征以及包括BCL2、CD34、CDX2、P63、CK7和CK20等标志物的广泛免疫组化检测结果的支持，还有一个泛黑色素瘤检测组。这些发现的组合有效地排除了肉瘤样癌、黑色素瘤和胃肠道间质瘤（GIST）等主要鉴别诊断，支持了MPNST的最终诊断。患者术后恢复顺利。本病例说明了非典型肛门直肠部位MPNST的诊断复杂性，并强调了进行全面组织病理学和免疫组化评估的必要性。早期识别和完整手术切除对于改善此类罕见病例的预后至关重要。讨论部分承认了与无法进行分子检测相关的局限性。
