Atypical spindle cell proliferation of indeterminate biological potential

Case Presentation

A 39-year-old female with unremarkable medical history presented with severe, generalized gingival enlargement of all quadrants. The gingival swelling was present for six years but only recently caused discomfort in addition to increasing tooth mobility. The patient denied any constitutional symptoms and was not taking any medications. She did not have any cutaneous, ocular, or genital lesions. She has had three miscarriages in the past and of note, the patient's symptoms worsen during pregnancy. On clinical examination all four quadrants demonstrated diffuse maxillary and mandibular buccal and lingual erythematous gingival enlargement associated with displacement of teeth and associated mobility. Radiographs showed generalized horizontal bone loss in both the maxilla and mandible. The clinical differential diagnosis of the severe gingival swelling included acute leukemia, lymphoma, inflammatory bowel disease, plasma cell gingivitis, and drug-induced gingival overgrowth. An incisional biopsy demonstrated a densely cellular proliferation of spindle cells arranged in a storiform pattern of short fascicles suggestive of a mesenchymal proliferation. The connective tissue stroma also showed areas of atypical metaplastic osteoid and chondroid deposition. Small islands of clear cells reminiscent of odontogenic islands were found encased within the osteoid deposits. There were also aggregates of granular cells noted. A comprehensive IHC panel included SATB2 (diffusely positive), CD56 (+ve), SSTR2A (focal +ve), CK19 (-ve but highlighted odontogenic epithelial nests), and the following stains were negative: AFB/ZN, TLE-1, MUC-4, ERG, CK7, CK20, Desmin, STAT-6, S-100, SOX-10, CD34, CD99, CD68, CD45, Kappa/Lambda (polytypic), and Ki67 (low). Molecular work-up for phosphaturic mesenchymal tumor was performed and CISH for fibroblast growth factor 23 (FGF23) was negative.

Conclusion

The features are most likely to represent multifocal peripheral ossifying/odontogenic fibromatosis supported by diffuse SATB2 expression which suggests origin from the periodontal ligament. Additionally, the findings may be in part related to an underlying undiagnosed genetic/hereditary etiology.