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

2. INTRODUCTIONINTRODUCTION  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.  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. METHODSMETHODS  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.  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. RESULTSRESULTS  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.  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. An intimate admixture of bland spin- dle cells and mature adipocytes 1 2 2 3 1 23 2 3 Features of solitary fibrous tumour in addition to foci of mature adipocytes

6. Cellular area with mitotic activity and cytological atypia 1 2 2 3 1 23 2 3 3 4

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

8. CONCLUSIONSCONCLUSIONS  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.  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. CONCLUSIONSCONCLUSIONS  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 : 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. 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.  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 : 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. 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.