Imaging Appearance ofSMARCB1(INI1)-Deficient Sinonasal Carcinoma: A Newly Described Sinonasal Malignancy

Abstract

SUMMARY: SMARCB1 (INI1)-deficient sinonasal carcinomas were first described in 2014, and this series of 17 cases represents the first imaging description. This tumor is part of a larger group of SMARCB1-deficient neoplasms, characterized by aggressive behavior and a rhabdoid cytopathologic appearance, that affect multiple anatomic sites. Clinical and imaging features overlap considerably with other aggressive sinonasal malignancies such as sinonasal undifferentiated carcinoma, which represents a common initial pathologic diagnosis in this entity. SMARCB1 (INI1)-deficient sinonasal tumors occurred most frequently in the nasoethmoidal region with invasion of the adjacent orbit and anterior cranial fossa. Avid contrast enhancement, intermediate to low T2 signal, and FDG avidity were frequent imaging features. Approximately half of the lesions demonstrated calcification, some with an unusual "hair on end" appearance, suggesting aggressive periosteal reaction.

Imaging Review of New and Emerging Sinonasal Tumors and Tumor-like Entities from the Fourth Edition of theWorld Health Organization Classification of Head and Neck Tumors

“…49 All cases were FDG-avid. 49 Diagnostic Tips and Differentials. Within the broad differential for locally aggressive sinonasal tumors, including SNUC and other carcinomas, SMARCB1-deficient sinonasal carcinoma di- agnosis is dependent on tissue sampling.…”

“…Eight cases had dural involvement, with extension through the dura in 3 cases. 49 On CT, the tumors are isodense to muscle, with calcifications in half of the reported cases. Both expansile and erosive patterns of bony involvement along the skull base are described with a "hair on end" pattern of periosteal reaction in several cases.…”

“…Both expansile and erosive patterns of bony involvement along the skull base are described with a "hair on end" pattern of periosteal reaction in several cases. 49 On MR imaging, most lesions are isointense on T1WI and variable on T2WI relative to the cortex, predominantly avidly enhancing with moderately restricted diffusion (Fig 8). 49 All cases were FDG-avid.…”

“…49 On MR imaging, most lesions are isointense on T1WI and variable on T2WI relative to the cortex, predominantly avidly enhancing with moderately restricted diffusion (Fig 8). 49 All cases were FDG-avid. 49 Diagnostic Tips and Differentials.…”

“…In an imaging analysis of 17 cases, 8 were centered within the nasoethmoid region. 49 The tumors are highly aggressive and infiltrative, many demonstrating local skull/brain invasion. Eight cases had dural involvement, with extension through the dura in 3 cases.…”