脂肪腫の再発と考えられた左肘部異型脂肪腫様腫瘍の1例

A Left-Arm Atypical Lipomatous Tumor That might be Lipoma Recurrence

はじめに

　異型脂肪腫様腫瘍（atypical lipomatous tumor）とは脂肪性腫瘍の中の1つであり，現在のWHO分類では良・悪性中間群に位置する腫瘍であると定められている 1）2）（ここで細胞学的に同位である高分化型脂肪肉腫は後腹膜臓器や筋層から出現する腫瘍を表し，異型脂肪腫様腫瘍は皮下組織に出現する腫瘍を表す）（図1）。

　特徴として，転移はまれであるが10～15 ％ほどが局所再発し，時間の経過とともに4 ％ほどが高悪性度に脱分化し脱分化型脂肪肉腫へ変異する可能性があるとされている 3）。

　今回われわれは，左肘部脂肪腫が再発する過程で，良悪性中間群である異型脂肪腫様腫瘍へ悪性転化した可能性のある，まれな1例を経験したので報告する。

　It is known that lipomas sometimes turn malignant, and we encountered the case of a man in his 50s with a benign lipoma in his elbow that later developed into an atypical lipomatous tumor. The result of the surgery performed to resect the recurrence of the patientʼs lipoma was the development of the atypical lipomatous tumor.

　Three factors had to be considered in order to manage this patientʼs case: (i) as mentioned above, lipomas do sometimes turn malignant; (ii) it is important to perform a biopsy if a benign tumor recurs; and (iii) other case reports have stated that a marginal resection instead of an extensive resection can be useful in order to not diminish the patientʼs quality of life, because a different type of recurrence of an atypical lipomatous tumor rarely happens.

　The tumor in our patientʼs elbow had been dealt with by a marginal resection. We have also identified many local recurrences at long-term follow-up appointments with patients who had undergone a marginal resection for a lipoma.