Introduction: Non-therapeutic or unnecessary operations can be performed in case of diagnostic difficulties, when a disease is established that absolutely needs surgical treatment. According to the modern active cytoreduction concept in oncology, all resectable metastases are removed with subsequent targeted therapy. Such treatment significantly increases the survival rate of patients. Serious problems arise in the diagnosis of metastasis in patients who have previously undergone splenectomy. Developing postsplenectomy splenosis (Sp) can simulate the presence of metastases and be an indication for unnecessary surgery. Although Sp was first described back in 1896, the mechanism of spleen revival after its removal remains completely unexplored. It is proved that in patients after post-traumatic splenectomy, abdominal Sp occurred in one-third of the patients 

Aim: To draw the attention of oncologists to the possibility of developing post-splenectomy splenosis, mimicking metastasis, in order to avoid unnecessary laparotomy

Materials and methods: This is the case report of a 44-year-old man, who  underwent  three years ago, a gastrectomy for cancer of the stomach. The spleen was damaged during the operation and splenectomy was performed. After discharge from the clinic, according to oncological standards, the patient was regularly examined to exclude the prolongation of the malignant process. At follow-up examination three years after surgery, аbdominal ultrasound revealed tumor-like formation in the left under diaphragmatic  space and two rounded lesions in the left lobe of the liver. CT scan confirmed this conclusion. Identified tumor formations were regarded as metastases, which became an indication for surgery. The patient underwent laparotomy, removal of the tumor of the left under the diaphragmatic space, resection of the left lobe of the liver. Surprisingly all excised tumors proved to have histological structure typical for the spleen without evidence of neoplasia, and finally, abdominal Sp  was diagnosed. 

Conclusions: In a patients with a splenectomy in the past abdominal Sp can mimic metastasis and become an indication for unnecessary surgery.