Retroperitoneal ectopic spleen identified during emergency laparotomy.

An ectopic spleen refers to splenic tissue or lobules located outside the normal anatomical position of the spleen and is most commonly found near the splenic hilum. Ectopic splenic tissue is typically found in characteristic anatomical locations but may rarely occur in atypical sites. Owing to its unusual localization, it can be radiologically mistaken for a variety of tumors. This case is notable because a large retroperitoneal mass requiring emergency laparotomy was ultimately diagnosed as ectopic splenic tissue. A 44-year-old man underwent emergency diagnostic laparotomy for acute abdominal symptoms. Preoperative imaging revealed a heterogeneous lesion medial to the left psoas muscle that was radiologically suggestive of a soft tissue tumor. Intraoperative frozen section examination demonstrated lymphoid tissue suggestive of splenic origin, and the diagnosis was subsequently confirmed on paraffin sections. Histopathological evaluation revealed a well-circumscribed nodular lesion composed of follicle-like lymphoid structures and sinusoidal vascular channels, consistent with ectopic splenic tissue. Unlike most reported cases, which typically occur in women aged 20-40 years and involve lesions measuring 1-3 cm, our patient was male and presented with a retroperitoneal lesion measuring 6.5×3×2.5 cm, an uncommon presentation. The unusual location and relatively large size of the lesion led to its initial radiological interpretation as a soft tissue tumor, highlighting the importance of comprehensive radiologic evaluation and histopathological examination for accurate diagnosis.