Sinonasal giant cell granuloma mimicking local recurrence after chemoradiotherapy for nasal cavity squamous cell carcinoma: A case report

Background: Giant cell granuloma is a benign osteoclast-rich lesion that most often involves the jaws and only exceptionally arises in the nasal cavity or paranasal sinuses. In a previously irradiated patient, a new enhancing sinonasal mass may strongly suggest recurrent malignancy, making histopathological confirmation essential.
Case presentation: A 50-year-old man with a history of squamous cell carcinoma of the left nasal cavity treated with definitive chemoradiotherapy four years earlier and followed by an initially favorable course was referred for a newly detected sinonasal mass. Contrast-enhanced computed tomography demonstrated a 47 × 30 × 57 mm tissue process centered on the posterior left nasal cavity, filling the nasopharynx and eroding the inferior wall of the left nasal cavity, without significant cervical lymphadenopathy. The radiological appearance raised concern for local recurrence. The patient underwent surgical resection under general anesthesia. Histological examination showed respiratory mucosa overlying a biphasic giant cell-rich proliferation composed of numerous osteoclast-like multinucleated giant cells and mononuclear spindle-shaped cells, with approximately three mitoses per 10 high-power fields and no atypical mitoses. Immunohistochemistry showed no p63 expression in the giant cells, moderate diffuse membranous and cytoplasmic CD163 expression in the giant-cell population, and a Ki-67 labeling index of approximately 20% in histiocytic cells. The overall morphological and immunohistochemical findings supported the diagnosis of a giant cell granuloma rather than recurrent squamous cell carcinoma. At one year, nasofibroscopic follow-up was normal, without evidence of residual or recurrent disease.
Conclusion: Sinonasal giant cell granuloma is a rare but important benign mimic of recurrent cancer. In patients previously treated for sinonasal malignancy, imaging alone cannot reliably distinguish recurrence from a giant cell-rich reactive or neoplastic lesion. Diagnosis requires careful clinicoradiological correlation, representative tissue sampling, exclusion of hyperparathyroidism, and, when necessary, ancillary testing to exclude giant cell tumor of bone and other osteoclast-rich lesions.