The majority of soft tissue tumors are benign and foremost lipomatous, and soft tissue sarcomas are overall rarely diagnosed. However, 20% of all sarcomas are diagnosed by so-called whoops- or unplanned surgeries, assuming the lesion to be a lipoma. In this case, the surgeon follows the strategy that any lump needs to be removed anyway in order to analyze it and establish the diagnosis.

A 37-year-female presented with a lump on her proximal right thigh which she noticed 2 months ago. It measured 30mm in size and was located epifascially on palpation. The treating physician did not decide to perform any imaging and removed it to establish the diagnosis, with direct closure of the skin.

Postoperatively, a severe hematoma extending down to the thigh was noticed. The work-up of the lump revealed an epithelioid sarcoma of the proximal type, which was not removed completely. This tumor classifies as aggressive, both systemically (with metastasis to the lungs) and locally, leading to regional metastases through the locally spread satellite tumor cells. Postfestum MRI was performed to determine the extent of local changes, preoperative radiation therapy was initiated to then locally resect the integument with a large area. The large defect was covered using a SCIP flap including lymphovenous anastomosis to prevent lymph edema of the extremity. At six month followup, the patient was tumor free and the local situation healed up uneventfully.

Whoops surgeries remain a vexing problem in the treatment of sarcoma patients, representing an over decades unchanged high rate of 20%. Not only is the local control but also survival compromised, it usually leads to major resections and reconstructions with deleterious functional consequences for the patients. Therefore, whenever there is an unknown lump of the soft tissues, MR imaging and getting an US-biopsy must be considered. If clinically there is a “classic” lipoma and it is decided to resect, complete resection is mandatory.