Intramuscular lipoma in thenar or hypothenar muscles.

We report on six patients of intramuscular lipoma of the hand. Four of them occurred in the thenar muscles and two in the hypothenar muscles. The mean age was 49 years (7-68 years). The duration of the lesions prior to excision was averaged as 35 months (12-60 months). Preoperative MRI was taken in all patients, and it was very useful for the diagnosis and differentiation between four well-circumscribed types and two infiltrative types. All operations were performed under loupe magnification. Preoperatively four patients with thenar lipoma had difficulty in moving their thumbs. Two out of four patients with lipomas in the thenar muscles had preoperative intermittent paresthesia and hyperesthesia caused by compression of the radial digital nerve of the thumb. Two patients with lipoma in the hypothenar eminence complained of difficulty with strong grip. The average diameter of the thenar group in its longest dimension was 5.2 cm (3-7 cm), and those of the hypothenar group was 5.5 cm (4-7 cm). At a mean follow-up of 55 months (21-91 months), no tumour had recurred.