PMC5466594_01
H&E: Well circumscribed unencapsulated tumour with vaguely nodular areas. The tumour contains epithelioid and spindled cells showing moderate atypia, with admixed osteoclast-like giant cells. There are areas within the tumour showing metaplastic bone formation, extramedullary haematopoiesis, sclerosis and mature adipose tissue. 1.1 Epithelioid haemangioendothelioma (H&E x3 Magnification) Well circumscribed, unencapsulated tumour. 1.2 Epithelioid haemangioendothelioma (H&E x25 Magnification) Vaguely nodular tumour areas. 1.3 Epithelioid haemangioendothelioma (H&E x200 Magnification) Epithelioid and spindled cells. 1.4 Epithelioid haemangioendothelioma (H&E x200 Magnification) Epithelioid and spindled cells. 1.5 Epithelioid haemangioendothelioma (H&E x200 Magnification) Osteoclast-like giant cells. 1.6 Epithelioid haemangioendothelioma (H&E x200 Magnification) Metaplastic bone formation. 1.7 Epithelioid haemangioendothelioma (H&E x200 Magnification) Extramedullary haematopoiesis. 1.8 Epithelioid haemangioendothelioma (H&E x200 Magnification) Sclerotic areas. 1.9 Epithelioid haemangioendothelioma (H&E x200 Magnification) Haemosiderin-laden macrophages within tumour.
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Microscopically the mass appeared well circumscribed but unencapsulated (Fig. 1.1). It was predominantly formed by vague nodular areas (Fig. 1.2) consisting of proliferating epithelioid and spindled cells (Figs. 1.3-1.4) with admixed osteoclast-like giant cells (Fig. 1.5), intervening mature adipose tissue and sclerotic stroma (Fig. 1.8). There were also areas of extramedullary haematopoiesis displaying trilineage differentiation (Fig. 1.7); metaplastic bone formation (Fig. 1.6); and smooth muscle clusters.
Immunohistochemistry: Immunohistochemistry highlights that the tumour cells are positive for vascular markers CD31 and CD34. Non-specific CD56 stating is present. SMA shows the presence of intersecting smooth muscle fibres, whilst Desmin is negative. Melanocytic marker Melan-A and neuroendocrine marker Synaptophysin are both negative. Mib-1 proliferation index is low; <5%. 2.1 Epithelioid haemangioendothelioma CD31 x 100 Magnification. 2.2 Epithelioid haemangioendothelioma CD34 x 100 Magnification. 2.3 Epithelioid haemangioendothelioma CD56 x 100 Magnification. 2.4 Epithelioid haemangioendothelioma SMA x100 Magnification. 2.5 Epithelioid haemangioendothelioma Desmin x100 Magnification. 2.6 Epithelioid haemangioendothelioma Synaptophysin x100 Magnification. 2.7 Epithelioid haemangioendothelioma Melan-A x100 Magnification. 2.8 Epithelioid haemangioendothelioma Mib-1x100 Magnification.
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Immunohistochemistry showed the tumour cells were positive for vascular markers CD31 (Fig. 2.1) and CD34 (Fig. 2.2), with SMA evidencing intersecting smooth muscle fibres (Fig. 2.4). CD56 staining (Fig. 2.3). Cytokeratins (CEA, EMA, CAM2.4, MNF116), meuroendocrine markers (Synaptophysin, Chromogranin), melanoma markers (S100, Melan-A, HMB-45), skeletal muscle markers (Myogenin, MyoD1), thymic lymphocyte marker (TdT), GIST markers (CD117, DOG1) and neural markers (S100, GFAP) were all negative (Figs. 2.5-2.8). Mib-1 proliferation index was low at less than 5%.