Indian Journal of Pathology and Microbiology

CASE REPORT
Year
: 2013  |  Volume : 56  |  Issue : 4  |  Page : 419--421

Primary subcutaneous mixed-type liposarcoma of the thigh showing three simultaneous dedifferentiations: Report of an unusual case


Shashikant C.U Patne1, Mohan Kumar1, Anjali Vishwanath2, Manoj Pandey3,  
1 Departments of Pathology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India
2 Department of Pathology, University College of Medical Sciences, New Delhi, India
3 Department of Surgical Oncology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh; Director, Bhopal Memorial Hospital & Research Centre, Karondh, Bhopal; Director Incharge, National Institute of Research on Environmental Health, Kamla Nehru Hospital, Bhopal, India

Correspondence Address:
Shashikant C.U Patne
Department of Pathology, Institute of Medical Sciences, Banaras Hindu University, Varanasi - 221 005, Uttar Pradesh
India

Abstract

Liposarcoma most commonly occurs in deep soft tissues of the limb and the retroperitoneum; however, its occurrence in the subcutaneous tissue is rare. Mixed-type liposarcoma (MTL) is the rarest subtype. We herein describe a unique case of MTL with three simultaneous dedifferentiations occurring in subcutaneous tissue of left thigh in a 45-year-old male. We briefly review the pertinent literature and report this case because of extreme rarity.



How to cite this article:
Patne SC, Kumar M, Vishwanath A, Pandey M. Primary subcutaneous mixed-type liposarcoma of the thigh showing three simultaneous dedifferentiations: Report of an unusual case.Indian J Pathol Microbiol 2013;56:419-421


How to cite this URL:
Patne SC, Kumar M, Vishwanath A, Pandey M. Primary subcutaneous mixed-type liposarcoma of the thigh showing three simultaneous dedifferentiations: Report of an unusual case. Indian J Pathol Microbiol [serial online] 2013 [cited 2020 Jun 6 ];56:419-421
Available from: http://www.ijpmonline.org/text.asp?2013/56/4/419/125358


Full Text

 Introduction



Liposarcoma (LPS) is the malignant mesenchymal tumor containing a variable number of lipoblasts. It is a tumor of adulthood that mostly occurs in the deep soft tissues of the limbs and the retroperitoneum. The occurrence of LPS in the subcutaneous tissue is rare. [1] LPS is currently classified by the World Health Organization into: (a) Well-differentiated LPS/atypical lipomatous tumor, (b) dedifferentiated LPS, (c) myxoid/round cell LPS, (d) pleomorphic LPS, (e) mixed-type LPS. [1] Of these subtypes, the mixed-type LPS (MTL) is the rarest, accounting for 4% of all LPS. [2] The so-called combined or MTL is defined by the presence of more than one morphological sub-type of LPS. Further, dedifferentiation in a MTL is quite uncommon. Our literature review revealed only five previously described cases of dedifferentiated MTL, which are reviewed and compared in [Table 1]. We herein report a unique case of MTL of subcutaneous tissue of the left thigh showing three simultaneous dedifferentiations.{Table 1}

 Case Report



A 45-year-old gentleman presented with a mass over lateral aspect of the left thigh since last 1 year. The mass had grown rapidly in the past 3 months with surface ulceration and intermittent spontaneous bleeding. Local examination showed an ulceroproliferative, soft to firm growth of size 6 × 5 cm. There was no history of trauma. Magnetic resonance imaging (MRI) revealed a heterogenous T2 hyperintense and T1 iso-hypointense lobulated mass lesion in the subcutaneous tissue plane on the lateral aspect of left upper thigh. No invasion of the underlying muscle and bone was seen. The MRI findings were suggestive of soft tissue sarcoma. An X-ray of the chest was normal. Fine needle aspiration cytology of the mass was diagnosed as pleomorphic sarcoma. The preoperative laboratory investigations were within the normal limits. A wide local excision of the tumor with primary closure and skin grafting was done. On gross examination, a multilobular tumor measuring 6 × 5.5 × 5 cm was present in the subcutis. The cut surface was solid grey white firm with bluish translucent and brown areas [Figure 1]. Microscopic examination showed three distinguished sarcomatous components: pleomorphic LPS, dedifferentiated part, and well-differentiated LPS. The three components formed approximately 60%, 30%, and 10% of the tumor area, respectively. The pleomorphic LPS extended from the dermis [Figure 2]a to deep subcutis and showed florid mitoses (mitotic count 40-50/10 HPF), formation of many tumor giant cells resembling high grade sarcoma along with variable numbers of pleomorphic, hyperchromatic, and multivacuolated lipoblasts [Figure 2]b. The presence of hyaline globules was also noted. At places, the tumor cells infiltrated the overlying epidermis. The pleomorphic liposarcomatous area was sharply demarcated from a small area of well-differentiated LPS [Figure 2]c, which was composed of adipocytes with marked variation in size, shape, and nuclear atypia and occasional intracellular hyaline globules [Figure 2]d. The pleomorphic LPS component showed gradual transition into a dedifferentiated zone. The dedifferentiated zone was comprised predominantly of malignant fibrous histiocytoma (MFH)-like area. There were small focus of hemorrhage and necrosis. The MFH-like area merged with the high grade osteo- and chondro-sarcomatous components. The three dedifferentiated components blended freely with each other in a mosaic fashion. Based on these findings, a final diagnosis of mixed-type (pleomorphic and well-differentiated) LPS showing simultaneous dedifferentiations into MFH-like and high-grade osteo-chondrosarcomas was made. All the surgically resected margins including the deep margin were free of tumor infiltration. The patient received postoperative chemotherapy and was kept under regular follow up. However, 15 months after the surgery, the patient developed bilateral pulmonary metastasis with mediastinal lymphadenopathy. A biopsy of the lung lesions showed pleomorphic LPS/MFH-like histology reminiscent of the primary tumor in the left thigh. At the last follow up, the patient was being treated with chemotherapy for the pulmonary metastasis.{Figure 1}{Figure 2}

 Discussion



We herein described an extremely rare occurrence of MTL of subcutaneous location in left thigh with three simultaneous dedifferentiations. As was noticed in our case, recent rapid growth in a lipomatous tumor is indicative of dedifferentiation. Dedifferentiation is defined by the juxtaposition of a non-lipogenic sarcoma to well-differentiated LPS/atypical lipomatous tumor. [1] Although MFH-like and intermediate to high-grade myxofibrosarcomas are the most common dedifferentiated components, heterologous differentiation occurs in 5-10% cases of dedifferentiated LPS. Most common heterologous element is myosarcoma (leiomyosarcoma/rhabdomyosarcoma), osteosarcomatous element is described in few cases, while chondrosarcoma is the rarest heterologous component. [6] The simultaneous presence of three dedifferentiated components in this case is unique as the reported cases of dedifferentiated LPS usually exhibit dedifferentiation in a single lineage. The most common site of dedifferentiated LPS is retroperitoneum followed by the extremities. However, only 2% of dedifferentiated LPS involve the superficial or subcutaneous site. [7] The presence of dedifferentiated component confers an aggressive biological behavior with a local recurrence rate of 41%, a metastasis rate of 17%, and a disease-related mortality of 28%. [7] Anatomic site is the most important prognostic determinant. Dedifferentiation in retroperitoneum carries a far worse prognosis than those in the accessible soft tissue (e.g., extremities). [7] Nevertheless, dedifferentiated component of the extremity is also capable of metastasis as occurred in our case. Surgical excision is the treatment of choice with the use of chemotherapy in metastatic disease.

References

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