16 May 2007 – Case of the Week #84
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Case of the Week #84
Clinical History
A 58 year old woman with no prior history presented with chronic sinusitis and underwent FESS (Functional Endoscopic Sinus Surgery).
Micro images: image #1; #2; #3; #4
Immunostains: CD34; smooth muscle actin
What is your diagnosis?
Diagnosis:
Sinonasal hemangiopericytoma
Discussion
The specimen shows surface respiratory epithelium overlying the diffuse growth of bland spindled or round/oval cells. There are prominent blood vessels with a staghorn appearance and perivascular hyalinization. There is no / mild atypia, no necrosis and no significant mitotic activity. The CD34 immunostain highlights the vascular endothelium but not the tumor cells. However, the tumor cells are strongly immunoreactive for smooth muscle actin.
Sinonasal hemangiopericytoma is an uncommon tumor of pericytic myoid differentiation. The World Health Organization calls it glomangiopericytoma, and others have suggested it be called myopericytoma (J Laryngol Otol 2007 Apr 10:1 [Epub ahead of print]). It typically affects older adults, with a mean age of 63 years, but may occur in children. There is often a history of airway obstruction or epistaxis in the nasal cavity or paranasal sinuses.
The histology in this case is typical. In addition, there is often a prominent inflammatory infiltrate containing eosinophils and mast cells.
Almost all cases are immunoreactive for vimentin and smooth muscle actin, with less common staining for muscle specific actin (77%) and factor XIIIa (78%). The tumor cells are negative for cytokeratin, and usually for the vascular markers CD31, CD34 and factor VIII.
Electron microscopy shows that these tumors have true pericytic differentiation, with numerous intracytoplasmic thin filaments with dense bodies, irregular basement membrane-like materials, a continuous basement membrane separating tumor cells from capillaries and occasional intercellular junctions (image).
The differential diagnosis includes lobular capillary hemangioma, solitary fibrous tumor and glomus tumor. Lobular capillary hemangioma has a low power lobular pattern. Although spindled fibroblasts and blood vessels are prominent, the overall picture resembles granulation tissue, and capillaries are small. Solitary fibrous tumor has a “patternless” pattern, with ropey keloid type collagen. The vascular pattern is similar to sinonasal hemangiopericytoma, but a recent study found that the vessels in sinonasal hemangiopericytoma were always D2-40 positive (a marker of lymphatic endothelium) in contrast to solitary fibrous tumors / soft tissue hemangiopericytomas, which were always D2-40 negative (Virchows Arch 2006;448:459). Finally, although a glomus tumor is also a pericytic tumor and has a similar staining pattern, it is extremely rare in the sinonasal region. In addition, its morphology is different, as it typically is composed of compact epithelioid cells.
Excision of sinonasal hemangiopericytoma is adequate treatment. However, since these tumors recur 18% of the time, follow up is necessary. There are no metastases, and these tumors only rarely cause death.
Additional references: AJSP 2003;27:737, Archives 2001;125:686
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