Answer: Pyogenic granuloma

Histology: The overlying surface epithelium is hyperplastic and centrally ulcerated. The underlying stroma is acutely inflamed and filled with a highly cellular proliferation of epithelioid cells arranged in clusters. Mitotic figures are readily identified. At the edge of the specimen one can better appreciated the fundamental architectural pattern of the lesion. Here lobules of tightly packed capillaries surround a central larger feeding vessel.

Discussion: Pyogenic granuloma is a benign acquired polypoid form of capillary hemangioma of the oral cavity that is histologically characterized by a lobular arrangement of proliferating small blood vessels. The time-honored term pyogenic granuloma draws attention to common secondary changes including ulceration and inflammation, but the lesion is neither an infectious or granulomatous process. The alternative designation of “lobular capillary hemangioma” better reflects its true essence.

Pyogenic granuloma occurs in all age groups. In the head and neck, they typically arise within the oral cavity or nasal cavity. The clinical presentation is that of a non-painful, purple-red polypoid mass that is friable and bleeds easily.

The fundamental microscopic makeup is that of a lobulated capillary hemangioma. Each lobule consists of a compact proliferation of capillaries around a central larger feeding vessel. In the presence of ulceration, the stroma becomes inflamed and edematous, particularly in the superficial aspect of the lesion. When these secondary stromal changes are pronounced, the lobular pattern is lost and the distinction between a lobulated capillary hemangioma and an exuberant granulation tissue is obscured. The endothelial cells lining the capillaries are often plump with an epithelioid appearance. Mitotic activity is highly variable. When distortion of the typical lobular pattern has occurred, pyogenic can be confused with various benign and malignant processes. Inflammation with prominent stromal edema can be dismissed as exuberant granulation tissue. In these instances, histologic examination of the deeper aspect of the lesion represents the best prospect for identifying a preserved lobular arrangement of the vessels. Pyogenic granulomas with a predominant solid growth pattern and brisk mitotic activity can be mistaken for more aggressive vascular lesions such as angiosarcoma, Kaposi sarcoma, and hemangiopericytoma. When the endothelial cells in these solid areas take on a more epithelioid appearance, the lesion can mimic epithelioid hemangioma, angiolymphoid hyperplasia with eosinophilia, and even carcinoma or melanoma. Unlike malignant vascular, epithelial and melanocytic tumors, pyogenic granuloma is exophytic and circumscribed without infiltration of surrounding structures.