March 2016 Case of the Month

38 year-old woman presents with a gingival nodular lesion adjacent to right lower 2nd molar tooth.  The dentist removed the lesion and submitted the tissue to pathology for examination.  The following images are from the lesion.  What is your diagnosis?

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Low power view reveals a polypoid/nodular portion of squamous mucosa with partial erosion of the epithelium.

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The underlying stroma is composed of abundant reactive fibroblastic stromal cells, inflammatory cells, and irregular/lattice-like ossification.

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The stromal fibroblasts show bland nuclear cytology without mitotic activity.

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Low power view reveals a polypoid/nodular portion of squamous mucosa with partial erosion of the epithelium.

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March 2016 Case of the Month

   Answer: Peripheral Ossifying Fibroma

The histopathology and location of the lesion are consistent with a peripheral ossifying fibroma (POF).  This is a benign lesion that occurs almost exclusively on the gingiva, with a female predilection, and peak incidence in the 2nd decade.  The typical histologic features of POF include ulcerated/eroded squamous mucosa overlying reactive fibroblastic proliferation with foci of mineralization that may include dystrophic calcification to well-formed bone.  This lesion is a reactive, non-neoplastic process often attributed to some chronic irritant such as orthodontics, dentures, or trauma.  Although benign, POF may recur following incomplete excision.