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

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.

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.

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.

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

Cellular area with mitotic activity and cytological atypia

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

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.

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; ; 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; ;  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; ; 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; ; 2000.