Atypical Lipoma/Well Differentiated Liposarcoma, dedifferentiated to a Myxoid
Liposarcoma
Liposarcomas are one of the most common soft tissue sarcomas of adult life. Many
subtitles exist and exact diagnosis is often difficult.
Characteristics of Liposarcoma:
Liposarcomas are usually deeply located. (Lipomas usually occur in superficial,
soft tissue).
They rarely if ever develop from benign lipomas.
Proper sampling of the gross tumor is critical for proper diagnosis.
Liposarcomas occur rarely in children.
Liposarcomas are less well defined than lipomas.
Liposarcomas may become very large.
Atypical Lipoma/Well Differentiated Liposarcoma/Atypical Lipomatous Tumor
Characteristics are:
Usually does not metastasize but often recurs
Often deep and large
May have bizarre stromal cells
50% in the extremities may recur
Small % over time dedifferentiate to a high grade malignant tumor
After 7-8 years, as long as 17-20 years after original dx
17% mets, 28% die of their disease
I - 3022-03, 3022-04 This 65 year old white male banker and scratch golfer was seen on
2-3-1995 with a large soft tissue mass in his left posterior thigh present for many months
which had become painful. On examination the left thigh demonstrated a huge soft tissue
mass with increased circumference of 12 cm over that of the right thigh. These
radiographs of the involved thigh demonstrate a large, soft, tumor mass which is less
dense radiographically than the adjacent muscle. This less dense mass indicates the
presence of fat and suggests the diagnosis of an intramuscular Lipoma. This x-ray can be
considered a ”poor man’s” MRI in detecting a fatty tumor. However, it cannot
differentiate between a benign or malignant fatty tumor. The underlying bone appeared
normal. He has unrelated degenerative arthritis of both hips.
3022-02, 3022-06 These MRI’s demonstrate a large soft tissue tumor mass compatible
with the diagnosis of an intramuscular Lipoma. These MRI findings, are often found in
benign Lipomas because of the obvious fat and is unusual in Liposarcomas. Chest x-ray
was clear. He also had atrial fibrillation and coronary artery disease but was in good
general health.
3022-07, 3022-08 The soft tissue tumor mass considered to be a benign Lipoma was
resected. It measured 29 x 24 x 6 cm and weighed 1.5 kilograms. Multiple sections,
throughout the mass, showed areas of fat necrosis. The final diagnosis by the Pathologist
was Lipoma with areas of organized fat necrosis.
(1995) Images, 4, 5, 6 These histosections made from the tumor mass demonstrate a
fairly typical Lipoma although some lipoblastic pleomorphism was found indicating this
could be an atypical Lipoma. Multiple sections showed bizarre stromal cells were
present which strongly suggest an Atypical Lipoma/well differentiated Liposarcoma. In
either case, Lipoma or atypical Lipoma, metastasis does not occur but recurrence
particularly in atypical Lipoma is not uncommon. Several days after surgery, the patient
did develop extensive cellulitis in the posterior thigh adjacent to the operative incision.
Needle aspiration of the cellulitis was negative. Pus was not found. An organism was
not obtained. The patient was placed on oral antibiotics and over several weeks the
cellulitis subsided. The patient then did very well for many years.
II -Images 12, 14, 22 Ten years later in May of 2005, at Warren General Hospital in
Warren PA., a resection of the large recurrence of the Lipoma was performed in a
hospital close to his home in Pennsylvania. These sections from this recurrence do show
some cells with bizarre nuclei and probably represents recurrent Atypical/well
differentiated Liposarcoma.
III - Img_6604, Img_6605 However, four years later in 2009, the second resection of an
enormous, soft tissue recurrence which had rapidly developed in his posterior left thigh.
Chest x-ray was normal. These two MRI’s demonstrate the enormous recurrence.
Histosections of the biopsy of the rapidly growing recurrence demonstrated a myxoid
Liposarcoma, medium grade quite different from earlier biopsy interpretations.
Images 24, 25, 29 In March of 2009, several months after the latest biopsy, a marginal
excision of the myxoid Liposarcoma was performed at RPCI including removing portions
of the gluteus maximus, gracilis and including neurolysis of the sciatic nerve. This mass
was 45 cm. in maximal diameter and weighed 6100 grams. The operative incision
extended from his buttock to the popliteal space. Because all of the adjacent soft tissue
was not removed at this resection, biopsy of residual tissues demonstrated myxoid
Liposarcoma. Thus only a marginal resection was performed. He was given 70.4 Gy of
adjuvant radiation because of the still present Liposarcoma in the patient.
Summary of treatments
1.
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3.
4.
Initial resection 1995-Atypical Lipoma/Well differentiated Liposarcoma
Resection of first recurrence in 2005- same diagnosis
Resection of second recurrence in 2009- Dedifferentiated Myxoid Liposarcoma
Post op radiation 70.4 Gy of adjuvant radiation
Phone call to the patient on 8-25-2011 indicates that he is 82 years old and “free of
tumor.” On the phone, he told me his posterior thigh was markedly scarred by prior
surgery but as far as he knows is “without evidence of recurrence.” However, he has
persistent pain now, 10-2011, behind his knee and leg thought to be due to the radiation.
However, he continues to have trouble with his leg. Chest x-rays every 6 months have
been normal. He has retired from banking and feels good. His hips are bad and he could
only walk one block easily.
Learning Issues:
There are several possible scenarios in this case. We believe the initial diagnosis in 1995
because of its deep location in the posterior thigh, its large size and the bizarre
appearance of the stromal cells that the most likely diagnosis was atypical Lipoma/well
differentiated Liposarcoma. If tissue blocks from the initial 1995 surgery were available
an MDM2 stain could have confirmed the diagnosis of Atypical Lipoma/well
differentiated Liposarcoma. This lesion recurs often but does not metastasize.
Ten years later in 2005, the lesion recurred and was resected in a hospital near his home
in Warren, Pennsylvania. The diagnosis of this tissue removed remains atypical
Lipoma/well differentiated Liposarcoma in our opinion.
In 2009, four years after the resection of the first recurrence, a massive recurrence
occurred, which on biopsy revealed a fully malignant myxoid Liposarcoma. This
indicated that the lesion had dedifferentiated to a fully malignant tumor. A marginal
resection of this enormous tumor was performed at RPCI and he was given heavy, local
post op radiation. Radiation is not usually very effective against Liposarcoma.
Thus, 16 years after his first treatment and two years after his marginal resection of the
myxoid Liposarcoma he remains liable to further recurrence, metastasis or the
development of radiation Sarcoma. He needs further follow up studies. CT scan of his
lungs and MRI of his thigh are being planned.