Retroperitoneal Inflammatory Liposarcoma in a Patient with Non-Hodgkin Lymphoma: A Report Highlighting Diagnostic Pitfalls

Well differentiated liposarcoma (WDLS) is the commonest subtype of liposarcoma. Recognised subtypes of WDLSs are lipoma-like, sclerosing, spindle cell and inflammatory. The inflammatory variant of WDLS also known as “lymphocyte-rich liposarcoma” is rare. We present a case of inflammatory WDLS occurring in the retroperitoneum, in a patient with a past history of non-Hodgkin lymphoma. We outline the histological features, discuss the differential diagnoses and highlight the diagnostic pitfalls in interpretation of this lesion on fine needle biopsy. Well-differentiated liposarcoma (WDLS) is the commonest subtype of liposarcoma, accounting for 40%–45% of all cases [1]. Because WDLS does not metastasize unless dedifferentiation supervenes, it has recently been suggested that the term atypical lipomatous tumour be applied to those tumours occurring in superficial locations amenable to complete excision [1]. The most frequent site for WDLS is in the deep soft tissue of the thigh, followed by the retroperitoneum, paratesticular region, and mediastinum [1]. In the current WHO classification, recognised subtypes of WDLS are lipoma-like, sclerosing, spindle cell, and inflammatory [1]. The inflammatory variant of WDLS, also termed as “lymphocyte-rich liposarcoma,” is rare, accounting for only 2% of all liposarcomas in reported series [2, 3]. In this paper, we present a case of inflammatory WDLS occurring in the retroperitoneum, in a patient with a past history of non-Hodgkin lymphoma, discuss the differential diagnosis, and highlight diagnostic pitfalls. In 2005, a 67-year-old man of Uruguayan origin, with a background history of ischaemic heart disease, psoriasis, and reflux oesophagitis, underwent resection of a retroperitoneal inflammatory and sclerosing WDLS after investigation of abdominal pain. In 2006, diffuse large B cell lymphoma (DLBCL) was subsequently diagnosed in the femoral head and left ilium and treated with radiotherapy. In 2008 he experienced left-sided abdominal pain and was found to have recurrent nodules in the left renal bed. A computed tomography (CT) abdominal scan showed a mass in the surgical bed of the retroperitoneum containing multiple soft-tissue nodules and fat, suggestive of recurrent retroperitoneal liposarcoma. A fine needle biopsy (FNB) showed a mixed population of lymphoid cells consisting predominantly of medium-sized and large cells with a lesser number of small lymphocytes (Figure 1(a)). The medium-sized and large cells had open chromatin and multiple small nucleoli with a small amount of cytoplasm and showed occasional