Diagnostic errors in subcutaneous myxofibrosarcoma: a retrospective case series before referral to specialist in bone and soft tissue tumors.

Background: Malignant subcutaneous soft tissue sarcomas, including myxofibrosarcoma, are often misdiagnosed as benign soft tissue tumors by non-specialists. This study investigated the clinical features of subcutaneous myxofibrosarcoma before referral to our department specializing in bone and soft tissue tumors.

Methods: A retrospective case series analysis was conducted on 26 patients with subcutaneous myxofibrosarcoma who were referred to our department between 2013 and 2024.

Results: Of the 26 cases of subcutaneous myxofibrosarcoma referred to our department, 15 cases (57.7%) had "diagnostic errors before referral," including seven cases of referral delay of ˃6 months, three cases of tumor puncture performed without suspicion of a tumor, four cases of unplanned biopsy, and seven cases of unplanned excision. The average time from the patient's first visit at a medical institution to the referral to our department was 22.7 ± 40.4 months (median 5.0 months, range 1-148 months). We performed initial wide resection in seven patients, additional wide resection in four patients, wide resection for recurrence in two patients, and amputation in two patients.

Conclusions: Subcutaneous myxofibrosarcomas are rare; however, physicians who treat subcutaneous tumors need to be knowledgeable about them. This case series suggest that poorly planned biopsies may miss malignant tumors, and that careless puncturing may lead to deep invasion of the tumor. It also suggests that if you suspect a benign tumor, you should follow up with imaging, otherwise there is a possibility that it will lead to a significant delay in diagnosis.