Lymphoscintigraphy for Peri-Anal Squamous Cell Carcinoma: A Case Report of an Atypical Location for Sentinel Lymph Node

This case report describes a 41-year-old man with a progressively enlarging, painful vegetative lesion in the perianal region, ultimately diagnosed as squamous cell carcinoma (SCC), through a punch biopsy. Sentinel lymph node (SLN) mapping was performed via preoperative lymphoscintigraphy utilizing 99m Tc-Phytate. Notably, an SLN was identified in an atypical location, below the anterior superior iliac spine (ASIS) in the subcutaneous tissue, diverging from typical drainage patterns associated with perianal SCC. Surgical excision of the SLNs revealed no evidence of tumoral involvement. This case underscores the importance of personalized assessment with preoperative lymphoscintigraphy in atypical lymphatic drainage patterns for effective staging and treatment of malignancies such as peri-anal SCC.