Presentation
Slowly enlarging lump in the right thenar eminence first noticed 8 years ago. Pain on movement interferes with work.
Patient Data
DER: right
IZQ: left
FLEX MANO: thenar eminence
The thenar eminence of the right hand is imaged with a linear transducer. A voluminous expansive, heterogeneous, echogenic image with posterior dirty shadow is observed. It measures 3.45 x 1.82 x 2.3 cm, with a volume of 7.55 cm3.
In the third image, the right and left hand are compared at the level of the thenar eminence, showing intact left musculature.
A voluminous lesion is observed at the level of the thenar eminence, which extends towards the hypothenar area, passing under the flexor tendons and moving them anteriorly. It appears hyperintense on T1 and T2 and hypointense on STIR. In STIR, it presents subtle areas of hyperintensity at the level of the thenar eminence, due to the use of the hand and rubbing with objects (edema).
The lesion measures 6.2 x 3.4 x 2.1 cm (transverse diameter x cephalo-caudal x anteroposterior).
An ultrasound is performed as the first study with a probable diagnosis of lipoma but liposarcoma must be ruled out, so an MRI is suggested.
The fatty mass (lipoma) is confirmed by MRI.
Surgical resection is performed with 3 entry points, removing all visualized fatty remains.
Currently (5 days after surgery) the patient presents functional impairment, however, the mass and pain are absent.
It should be noted that the mass in the thenar eminence was present (although to a lesser extent) for 8 years, with continuous growth; however, our patient did not consult before since the mass did not cause discomfort.
Case Discussion
Lipoma is defined as a tumor of adipose lineage, i.e. formed by mature adipocytes. It can occur in multiple locations and various depths, e.g. subcutaneous to intramuscular or intermuscular, and can also adhere to the abdominal fascia.
It has its own fibrous capsule that separates it from adjacent structures (i.e. it is not derived from other structures), so at the time of surgical intervention it can be completely removed; it can recur if excision is incomplete.
Lipomas:
tend to be small tumors (less than 3 cm), malignancy should be suspected in any lipoma larger than 5 cm in maximum diameter
they present a homogeneous architecture, predominantly fat, and isolated fibrotic septa may be observed alternating with it; any lipoma with thick septa or a highly heterogeneous architecture should be suspected
On ultrasound: its echogenicity will depend on the surrounding structure and may be hyper/hypo or isoechogenic with its surroundings. It presents a well-defined capsule. Although one of its forms of presentation is "diffuse lipomatosis" where it is interspersed with the surrounding tissue.
It will be hyperintense on T1- and T2-weighted MR sequences with a drop in intensity in STIR or other fat suppression sequences. It has poor vascularization so any lipoma with abundant vascularization should be reevaluated to rule out liposarcoma.
Lipomas tend to appear in areas where there is abundant fatty tissue, i.e. neck, abdomen, thighs, back, being extremely rare in the acral area (hands or feet).
In the case of giant lipoma of the hand (our patient), it usually presents between 60-70 years of age, and manifests as a slow-growing mass that is ignored by the sufferer, since it does not generate symptoms until late, when it can cause compression of neighboring structures generating pain, paresthesia, hypoesthesia, etc.
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