Year : 2010 | Volume
: 53 | Issue : 2 | Page : 353--355
Dedifferentiated liposarcoma of the retro-peritoneum: Histologically low-grade type
Rugvedita Satyajeet Parakh, Meera Prem Zawar, Pradeep Achyut Gadgil, Neeraja Shashikant Kaujalagi
Department of Pathology, Dr. V. M. Government Medical College, Solapur, India
Rugvedita Satyajeet Parakh
Prem-Kamal, Station Road, Opp. Guru Chitra Mandir, Ichalkaranji-416 115
A dedifferentiated liposarcoma of the retro-peritoneum of a 45-year-old female is described in this case report. It showed dedifferentiation into a histological low-grade type and thus defies the traditional definition of dedifferentiated liposarcoma. The excised specimen was a huge, multi-nodular encapsulated mass surrounding the kidney and infiltrating into it. The mass showed a dedifferentiated focus different in color from the surrounding tumor and containing areas of necrosis and hemorrhage. The sections from the dedifferentiated part of the tumor appeared predominantly as benign spindle cell component on histology but the tumor was infiltrating into the kidney. Hence, a close and long-term follow-up is expected in such cases though they look benign. In the retro-peritoneum, a lipoma-like well-differentiated liposarcoma with spindle cell component, like the present tumor, which shows dedifferentiation, should not be overlooked.
|How to cite this article:|
Parakh RS, Zawar MP, Gadgil PA, Kaujalagi NS. Dedifferentiated liposarcoma of the retro-peritoneum: Histologically low-grade type.Indian J Pathol Microbiol 2010;53:353-355
|How to cite this URL:|
Parakh RS, Zawar MP, Gadgil PA, Kaujalagi NS. Dedifferentiated liposarcoma of the retro-peritoneum: Histologically low-grade type. Indian J Pathol Microbiol [serial online] 2010 [cited 2020 Jul 16 ];53:353-355
Available from: http://www.ijpmonline.org/text.asp?2010/53/2/353/64347
Dedifferentiated liposarcoma (DDL) was first described by Evans  in 1979 as a tumor composed of areas of a non-lipogenic sarcoma associated with an atypical lipomatous tumor (ALT)/well-differentiated liposarcoma (WDL). Liposarcomas are the most common sarcomas in adults, with most the common location in the retro-peritoneum.
The dedifferentiated component seen is usually high-grade, resembling malignant fibrous histiocytoma, fibrosarcoma, leiomyosarcoma. 
We report a case wherein a de novo lesion of the retro-peritoneum showed dedifferentiated liposarcoma of low grade and was composed predominantly of a benign-appearing spindle cell component with adipocytic component.
A 45-year-old woman presented with distension of abdomen since two months, rapidly growing in size. Her past medical and family history was not contributory to the present complaint. On per abdomen examination, a firm mass was palpated in the right lumbar region extending to the left hypochondrium through the umbilical region. Plain X-ray and computed tomography scan of the abdomen and pelvic cavity showed a well-defined mass of size 40 x 25 x 20 cm in the retro-peritoneum and a lipomatous tumor (Liposarcoma) was suspected on radiology.
The excised specimen consisted of a huge, multinodular, well-encapsulated mass of size 40 x 25 x 20 cm encircling the kidney. The specimen weighed 5.2 kg. It was rubbery, greasy and yellowish white on cut surface, giving a lipoma-like appearance. At one cut surface, the tumor showed a well-demarcated area of size 14 x 10 x 8 cm, tan in color [Figure 1]. This part contained friable tissue with areas of necrosis, hemorrhage and microcyst formation.
Multiple sections from the excised specimen were taken and processed conventionally. Sections from the lipoma-like area of the tumor showed an encapsulated tumor characterized by proliferation of adipocytes, which varied in size and shape [Figure 2]. Occasional multi-vacuolated lipoblasts were also seen.
The tan area was histologically different from the above-described areas. It showed a tumor composed of benign spindle-shaped cells and fat cells interspersed amongst them [Figure 3]. The spindle cells were loosely arranged in whorls and fascicles. The cells had bipolar bland-looking nuclei with inconspicuous nucleoli and scant cytoplasm. A small number of cells had irregularly shaped and bizarre nuclei. There were no mitotic figures. The fat cells showed very little variation in size and shape and very few multi-vacuolated lipoblasts were seen. The stroma showed dense mononuclear cell infiltration. Areas of necrosis were also seen. The sections taken from the kidney showed focal infiltration of tumor cells.
Dahlin  first coined the term dedifferentiation in the context of chondrosarcoma in 1971. He described it as a morphologically bimorphic neoplasm showing areas of well-differentiated, low-grade tumors juxtaposed with high-grade non-chondroblastic tumors without obvious areas of gradual transition.
In 1979, Harry Evans  used the term to describe a liposarcoma, which was characterized by a combination of well-differentiated liposarcoma and a non-lipogenic dedifferentiated sarcoma-like component.
The dedifferentiation may occur as a de novo phenomenon (also known as primary dedifferentiation, ab initio) or as dedifferentiation in the recurrence of a previous entirely well-differentiated liposarcoma. 
The original definition of dedifferentiated liposarcoma has been modified over the years and now includes dedifferentiation into exclusively low-grade areas or into a combination of low and high-grade areas.
Our case represents a low-grade dedifferentiated liposarcoma. The spindle cells in the liposarcoma are analogous to stellate mesenchymal cells of the primitive fat lobule.
Henricks et al., after the study of 155 dedifferentiated liposarcomas commented: "The behavior of liposarcoma in which the dedifferentiated component is entirely low-grade is similar to that of traditional dedifferentiated liposarcoma than to that of well-differentiated liposarcoma."
Their study also helped in the expansion of the conventional definition of dedifferentiated liposarcoma and suggested including the tumors with low-grade differentiation. It also concludes that the low-grade dedifferentiation represents a precursor lesion of high-grade dedifferentiation. In our case, the tumor infiltrated the kidney, which suggests a close follow-up of the patient.
In conventional dedifferentiated liposarcoma, the dedifferentiated component usually shows features resembling malignant fibrous histiocytoma, leiomyosarcoma, fibrosarcoma. Some of these tumors also display osteosarcomatous, rhabdomyosarcomatous areas.
In conclusion, the present tumor with the predominant benign-appearing spindle cell component was considered to be a low-grade dedifferentiated liposarcoma. Close and long-term follow-up is required even though the histo-morphology is benign per se.
Fukunaga  reported a similar case and we totally agree with his conclusion that 'In the retro-peritoneum, lipoma-like well-differentiated liposarcoma with areas of benign-appearing spindle cells should not be overlooked'.
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