Extramammary myofibroblastomas are rare benign tumors. Since the first report by McMenamin et al. in 2001,
approximately 150 cases of extramammary myofibroblastoma have been published.
Of note, a series by Howitt et al. comprised the largest proportion of the published cases of extramammary myofibroblastoma to date.
The anatomic distribution of these tumors is widespread, with the most common, general site of involvement being the groin/inguinal region.
Therefore, it has been theorized that extramammary myofibroblastomas occur along the embryonic milk‐line from the axilla to the medial groin.
Differential diagnosis for extramammary myofibroblastoma includes both benign and malignant tumors.
Although computed tomography and magnetic resonance imaging are considered valuable in the diagnosis of myofibroblastoma,
extramammary fibroblastoma is difficult to diagnose. Thus, the most appropriate diagnostic test for a clinically or radiologically evolving soft tissue mass is a biopsy.
Treatment strategy should be decided based on pathological diagnosis of biopsy specimen as well as preoperative imaging. In fact, if a malignant tumor is identified from biopsy, a combined resection of adjacent organs should be considered.Watari et al. reported a case of retroperitoneal myofibroblastoma in an 88‐year‐old male.
Since there have been a few cases of extramammary myofibroblastoma in the pelvic retroperitoneal space, this case was extremely rare in terms of describing detailed surgical treatment. Although extramammary myofibroblastomas are frequently asymptomatic and detected incidentally, large retroperitoneal myofibroblastomas may be accompanied by symptoms such as dysuria and malaise during defecation.
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In this case, the patient underwent surgical resection due to frequent urination and a “pushing up” sensation from the groin during defecation.
Successful treatment of the large retroperitoneal myofibroblastoma was achieved using laparoscopic radical surgery.
Thus, this report is of clinical value because few reports described the details of clinical course and surgical findings of extramammary myofibroblastomas. Obviously, the selection of open or laparoscopic procedure for tumors should be based on the individual case and the skill of surgeon. Therefore, when faced with a retroperitoneal soft tissue mass, which is detected incidentally or as a slow growing tumor, it is necessary to obtain a biopsy to rule out malignancy. If malignancy cannot be ruled out or the patient is symptomatic, surgical resection is appropriate.