# An Unusual Case of Hemosiderotic Fibrohistiocytic Lipomatous Lesion: Correlation of MRI and Pathologic Findings

Authors: Ronald S. A. de Vreeze; Wim Koops; Rick L. Haas; Frits van Coevorden
Journal: Sarcoma
 (2008)

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## Abstract

The spectrum of lipomatous lesions ranges from benign to highly malignant disease. Differentiation between these lesions is important to indicate prognosis and choose the most appropriate treatment. Hemosiderotic fibrohistiocytic lipomatous lesion (HFLL) is a rare subtype of lipomatous tumor. The diagnosis is usually based on clinical, histological, and immunohistochemical information. Where magnetic resonance (MR) imaging is a suitable modality to assess fatty tumors, no data is reported on MR imaging of HFLL. Here, the MR characteristics are described in correlation with pathologic findings in a case of HFLL in the left thigh, an unusual location.


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## Body

## 1. Introduction

The spectrum of lipomatous lesions ranges from benign to
highly malignant disease. Differentiation between these lesions is important to
indicate prognosis and choose the most appropriate treatment [1].The hemosiderotic fibrohistiocytic lipomatous lesion (HFLL) is
first described by Marshall-Taylor in 2000 [2]. The incidence of HFLL is estimated
to be less than 0.2% of all benign lipomatous lesions [2].There is an ongoing debate about the resemblance of early pleomorphic hyalinizing angiectatic tumor (PHAT) and HFLL; some consider HFLL a precursor lesion
of PHAT, implicating HFLL to be a neoplastic lesion [3, 4], others consider HFLL an individual
more reactive lesion [5, 6].Based on the cases described so far, HFLL is most common in
middle aged females, however there is a wide age spectrum. HFLL is typically
located on the distal extremities, particularly on the dorsal side of the foot
and may be associated with venous stasis and trauma [3]. The median size at clinical
presentation is 50 mm and ranges between 1 and 170 mm [2, 5]. Surgical removal is mainstay
treatment for this lesion.Local recurrences appear in approximately 50% of cases and
become apparent within one year [2, 5]. Distant metastases have not been
reported. Characteristic histopathological features are the spindled cells
morphology and the presence of variably prominent hemosiderin
pigment. The most common immunoprofile is diffuse staining of the spindled cell
with CD34.Previous data suggest that the appearance of lipomatous
tumors on magnetic resonance (MR) images is helpful in establishing a diagnosis
[7, 8]. To our knowledge, there are no other
reports describing the radiologic appearance of HFLL. We report on the imaging
features in correlation with pathologic findings in a case of HFLL in the left thigh,
an unusual location.


## 2. Case Report

A 66-year-old Caucasian man was sent to our tertiary referral
center for a lesion of the left thigh, nagging pain, uncertain radiological
diagnosis without histologic diagnosis. The patient had noticed the lesion one
and a half year before and it had slowly increased in size. Besides oral anticoagulation
treatment for atrial fibrillation, there was no relevant medical history, specifically
no trauma. Family history was noncontributory. Physical examination revealed a
resistance involving half the anterior medial side of the thigh. MR imaging was
performed.MR imaging, by Philips 3T Achieva and
intravenous contrast series with Dotarem, showed a lipomatous lesion of the
left thigh measuring 19×8×4 cm with irregular boundaries. The lesion showed
multiple far reaching intramuscular and subfascial extensions. The assessment
of internal structures showed a homogeneous, lobulated lesion. Figure 1
illustrates the high signal intensity of the lesion on T1- and T2 (STIR) weighted
images with foci of hyperintensity on the fat-saturated (STIR) images. The signal
intensity, particularly on T1 weighted images, was substantially lower than
that of surrounding subcutaneous lipomatous tissue. Dynamic MR imaging was
performed to characterize the enhancement pattern of the tumor, which showed homogeneous
enhancement.Upper left transversal T1 (TR 545 TE 20) and fat
saturated STIR image (TR 12000 TI 200 TE60) upper right, showing the thigh and
a homogenous lobulated mass. Coronal T1 and T2 weighted image is shown at the lower part
of Figure1, an image through left thigh showing a homogenous mass with irregular
boundaries.
(a)(b)(c)(d)These combined imaging features were suggestive for a benign
lesion or low grade sarcoma. However, we could not unequivocally define these
MR images to a specific diagnosis. As intermediate or high grade sarcoma could
not be ruled out, and these lesions in our institute are
preferably treated by preoperative radiotherapy, a trucut biopsy was performed. A thoracic
computed tomography scan was made which did not show distant metastasis.Histopathological analysis did not allow a definitive diagnosis and suggested a not otherwise
classifiable benign or low-grade lipomatous lesion; an intermediate or high-grade
liposarcoma was
unlikely.Based on these findings, a surgical resection was planned.The macroscopic aspect at surgery was a yellow-brown fatty gelatinous
lesion, 19 cm in diameter, poorly circumscribed, unencapsulated and extending along
muscles and neurovascular structures. A resection leaving no macroscopic
residue (R1) was performed.


## 3. Histopathological Analysis

After
resection specimens were histopathologically evaluated. Macroscopically, the unencapsulated lipomatous
lesion showed tissue that was darker yellow than the normal surrounding fat. Microscopically, twenty representative samples throughout the whole tumor were
reviewed on hematoxylin-eosin stained slides. In all of them, similar findings
were observed: the
lesion demonstrated mature adipose tissue with foci of proliferation of bland
floret-, spindled-, and giant- cell areas, extending along and between muscle
fibers. A lobular appearance was created by various small wide blood vessels
associated with thin fibrous septa. Around these vessels, histiocytes, mast and
plasma cells revealed the inflammatory parts of this tumor. The nuclei of the
spindled and multinucleated cells varied in diameter, the latter having a
Touton giant cell-like character. Occasionally larger nuclei were identified
but without atypia, and very sporadically mitoses were seen. Granular brown to
golden pigment and occasionally hyperchromatism was observed in the
interstitial space of tumor (see Figure2).The upper left image shows the histology of HFLL.
The upper right magnified image shows the spindled cell component of HFLL,
whereas the inflammatory component of HFLL is shown in the lower left image, and
macrophages with hemosiderin pigment (arrows) are shown in both the lower
images. In all illustrations, mature adipocytes are present.
(a)(b)(c)(d)Immunohistochemical analysis showed a notable staining primarily
of the spindled cells and multinucleated cells for CD34. S-100 was positive in
mature fat cells. CD31, PPARγ, and P53 were negative.By combining histology and immunohistochemistry of resected
specimen with clinical information, the
diagnosis HFLL following Marshall-Taylor and Brown’s classification was established
[2, 5].


## 4. Discussion

The discrimination between the various differential diagnoses
of fatty tumors is generally based on clinical, imaging, and histopathological
features, sometimes combined with immunohistochemical or molecular genetic features.
Besides clinical features suggesting malignancy, such as older age, large size,
fast growth-rate, there are MR features that suggest malignancy. These include
presence of nodular and/ or globular or nonadipose mass-like areas and a decreased
percentage of fat composition. The percentage and analysis of these nonfatty
regions in these lipomatous tumors help to distinguish between benign or malignant
lesions. Furthermore, two prior studies in lipomatous tumors have emphasized
that infiltrative margins may suggest the diagnosis of benign lipomatous lesion
rather than that of liposarcomas [9, 10].This case, unlike most described HFLL lesions, lacked a
history of prior trauma, presented at an unusual location and was large. However,
the macroscopic aspect, morphological and immunohistochemical features were
consistent with HFLL. The specific histological HFLL features could be correlated
to the MR characteristics. The fatty component of the tumor was macroscopically
darker brown than normal fat tissue and correlated with lower signal intensity of
the HFLL compared to the surrounding subcutaneous fat. The absence of a fibrous
capsule could be recognized with MR findings as well as the wide intramuscular
extension. The internal tumor structures seen on MR imaging were a reflection
of the characteristic fibrous bands in the overall histological architecture. The
spindled cell CD34 positive areas were corresponding to the enhanced parts of
the tumor on the MR images. The abundant homogenous adipose areas were reflecting
on MR imaging in the lobulated areas. The scarce specific iron deposition seen
at histopathological review however was not recognized on MR images or dynamic
gradient echo sequence, since the signal intensity on MR was not decreased by
iron deposition of HFLL. Furthermore, the typical inflammatory parts of HFLL could
not be correlated with characteristic MR features.Recently, Folpe and Weiss have proposed that early pleomorphic hyalinizing angietic
tumor has a presumed identical histology to HFLL [4]. Yet, the pathogenetic relationship
between these two lesions remains to be determined [3, 5, 6]. It must, however, be emphasized
that general awareness of HFLL allows physicians to reach a correct diagnosis.
The presence of only 26 HFLLs that have been histologically described so far
could be the main obstacle for physicians to be aware of such lesions.


## 5. Conclusion

This report shows the MR images of an unusual case of HFLL.



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*Source: 893918-2008-06-23.xml*