SMARCB1-Deficient Sinonasal Carcinoma: A Case Report and Systematic Review

Introduction: Carcinoma arising from the paranasal sinuses is uncommon, accounting for only 3% of all head and neck malignancies. Prognosis is generally dependent on tumor histology, with poorly differentiated carcinomas being particularly aggressive. These tumors typically present at advanced stages due to nonspecific symptoms and prognosis is poor. Recently basaloid squamous cell carcinoma displaying complete loss of nuclear SMARCB1/INI-1 has been described. This subtype accounts for ~6% of sinonasal carcinomas. In this report, we present a case of SMARCB1-deficient sinonasal carcinoma (SDSC) and systematically review the literature.

Case Presentation: A 21-year-old male presented to the emergency department for severe progressive headache and diplopia of three months duration. Computed tomography revealed a large skull base neoplasm arising from the cribriform plate and extending into the sphenoid sinus, obliterating the bony architecture. His examination was notably only for left medial rectus palsy. The process was initially presumed to be an esthesioneuroblastoma with no evidence of metastatic disease on imaging and was he was taken for endoscopic resection and skull base reconstruction with a combined neurological surgery and otolaryngology approach. The tumor was noted to extend over the cribriform plate with near total erosion of the bilateral ethmoid sinus roof with extension into the planum sphenoidale and left orbital apex with a small dural defect. Histologic examination of the tumor revealed epithelioid cells with loss of INI1 on immunohistochemistry. The final diagnosis was SDSC. The patient subsequently underwent stereotactic radiation therapy for residual disease.

Systematic Review: Systematic search was performed on July 26, 2019 and yielded 13 studies for final review. All studies were either case series or case reports with 82 cases of SDSC published since 2014. Age on presentation ranged from 19 to 75 years with the majority of patients being male. Surgical resection was the primary modality of treatment with adjuvant radiation or chemoradiation therapy. Overall, the prognosis was poor with most tumors presenting at advanced stages with median survival of 24 (15–26) months with 50% of patients dying of the disease and high rates of distant metastases (43.3% [27.1–66.7%]). Only 33.3% (20.8–43.3%) of patients had no evidence of disease at follow up with a median survival of 10.5 (8.8–40.5) months. Studies comparing SNUC to SDSC reported worse prognosis for SDSC and increased risk for locoregional recurrence in the latter cohort.

Discussion: SDSC represents a rare subtype of undifferentiated sinonasal carcinoma with only 82 reports of cases described in the literature. In general, this is a highly aggressive tumor presenting at advanced stage with propensity of metastasis. The majority of patients are treated with primary surgical resection and adjuvant radiation therapy or chemoradiotherapy though have poor prognosis with average survival at ~2 years from diagnosis. Given the nascent description of this entity in the literature and the unfavorable outcomes, it is important to recognize its presence and differentiate it from other undifferentiated carcinomas arising in the paranasal sinuses. More research is necessary to determine the optimal treatment modality and management