LIPOMATOUS HAEMANGIOPERICYTOMA: A CASE REPORT.

1. LIPOMATOUS HAEMANGIOPERICYTOMA: A CASE REPORT. NUNZIA SCIBETTA - LORENZO MARASA’ Department of Pathology, A.R.N.A.S. Civico, Palermo

2. INTRODUCTION • Lipomatous haemangiopericytoma (L-HPC) is an unusual tumor composed of mature adipocytes and HPC-like branching vessels, that shares many features with solitary fibrous tumour (SFT). • L-HPC present preferentially as deep-seated, (deep soft tissues of the lower extremity and retroperitoneum), well demarcated, slow-growing, almost non–recurring, non-metastasizing masses. They occur in middle-aged adults with a male predilection. • We describe the clinicopathologic and immunohisto-chemical features of a case of L-HPC, located in the retroperitoneum, wich contained hypercellular areas and showed increased mitotic activity and nuclear atypia.

3. METHODS • A 60 year old woman had a painless mass on the retroperitoneum with visceral compression sym-ptoms. Clinical examination did not give any indica-tion of metastasis. • The surgical specimen was fixed in buffered formalin, embedded in paraffin and stained with H&E. Immuno-histochemical studies were performed.

4. RESULTS • Grossly the tumor was well-demarcated and partially encapsulated, solid, tan yellow, with maximum diame-ter of 29 cm, with free margins. • Histologically it was composed of a admixture of be-nign lipomatous and haemangiopericytomatous com-ponents, including oval to round cells, surrounding a sinusoidal and staghorn vasculature with perivascular hyalinization. Mature fat occupied approximately one quarter of the area of tumour. • The tumour contained hypercellular areas showed 10 mitoses per 10 HPF, and moderate to severe nuclear atypia. • Neither lipoblasts, nor isolated atypical hyperchroma-tic cells within mature fat as are seen in well-differen-tiated liposarcoma, were present. • Immunohistochemically, they stained with antibodies to vimentin, CD34, BCL2, CD57, CD99, and not to al-pha-smooth muscle actin, desmin, S100 protein, EMA, CD31,CD117.

5. 2 1 2 Features of solitary fibrous tumour in addition to foci of mature adipocytes An intimate admixture of bland spin-dle cells and mature adipocytes 3 2 1 3 3 2

6. 3 1 2 2 1 4 Cellular area with mitotic activity and cytological atypia 3 2 3 3 2

7. IMMUNOHISTOCHEMICAL EXAMINATION Immunoreactivity of the tumour cells for CD57 Diffuse positivity for CD34 There is no staining for smooth muscle actin Immunoreactivity for vimentin

8. CONCLUSIONS • The histologic differential diagnosis of this neoplasm includes spindle-cell lipoma, angiolipoma, liposarco-mas, tumors showing smooth muscle and adipocytic differentiation, and haemangiopericytoma infiltrating fat. Histologically the our tumor resemble the cellular form of L-HPC and the immunoprofile is also similar to that of L-HPC. • Because of the small number of cases and limited follow-up, we cannot be certain of their biologic behavior .Criteria of malignancy include large tumour size, high cellularity, at least moderate to marked cytological atypia, tumor necrosis, numerous mitoses >4 mitoses per 10 HPF and /or infiltrative margins.

9. CONCLUSIONS • In our case the large tumor size, the presence of areas of increased cellularity with a mitotic index >4 mitoses per 10 HPF, and nuclear atipya are important predictors of poor outcome, and long-term follow-up is mandatory. MAIN REFERENCE : Guillou L:, Gebhard S. , Coindre JM. : Lipomatous hemangiopericytoma: a fat-containing variant of solitary fibrous tumor? Clinicopathologic, immuno-histochemi-cal, and ultrastructural analysis of a series in favour of a unifying concept. Hum. Pathol. 31; 1108-1115; 2000.