High-Grade Biphenotypic Sinonasal Sarcoma: A Case Report

Abstract

Introduction Biphenotypic sinonasal sarcoma (BSNS) is a recently found entity that first described by Lewis et al. It was then added to the 4th edition of the World Health Organization (WHO) of head and neck tumors in 2012. BSNS has been described as a rare low-grade sarcoma arising in the upper sinonasal tract. It is believed that in the past, BSNS was, likely, previously diagnosed as other low-grade or benign malignancies. Fibrosarcoma, leiomyosarcoma, and peripheral nerve sheath tumors, all fall within the differential diagnosis of BSNS. However, BSNS is unlike other mesenchymal sinonasal tumors, as it displays both neural and myogenic differentiation. BSNS has thus far been recognized in only a hand full of case reports, all of which have reported similar morphologic features of a low-grade soft tissue tumor with neural involvement arising from the nasal cavity or ethmoid air cells in middle aged individuals. In fact, being low-grade sarcoma became such a hallmark characteristic of this tumor that it even received the name low-grade sinonasal sarcoma with neural and myogenic features or LGSSNMF. Case Presentation We present, however, for the first time, a high-grade differentiation of BSNS in an otherwise healthy 72-year-old female. The patient was referred from an outside ENT (ear, nose, and throat) after pathology from a presumed polypectomy returned positive for a BSNS. Initial imaging revealed erosion through the bilateral lamina papyracea, anterior cranial fossa floor, and posterior table of the frontal sinus. She then underwent a combined endoscopic and bicoronal open approach for resection of the skull base lesion that was found to encompass the entirety of the sinonasal cavities bilaterally. Postoperatively, the patient underwent significant complications including infection of the pericranial flap, pneumocephalus, and eventually death. Discussion As BSNS is a fairly new entity, currently there has only been four case series conducted, each identifying features of a low-grade sarcoma with both myogenic and neural differentiation. Histologically, BSNS has monophasic spindle cells with uniform, elongated nuclei with scant cytoplasm between benign proliferations of surface-type respiratory epithelium, with a low mitotic rate. Our case, however, revealed pleomorphic hyperchromatic cells with high mitotic activity and necrosis with invasion of bone, staging it as high grade. Immunohistochemistry also differed from the previously reported standards. This case describes a new category for BSNS which may change the differential diagnosis, management, and surgical recommendations that are currently utilized for this skull base neoplasm.

Biphenotypic sinonasal sarcoma with PAX3::MAML3 fusion transforming into high-grade rhabdomyosarcoma: report of an emerging rare phenomenon

“…From the available description and figures, it seems that both cases showed a high-grade spindle cell morphology without the rhabdoid features detected in our case. Unfortunately, the first case was not tested for skeletal muscle markers at all [ 14 ], and the other was tested only for desmin and myogenin, both of which were focally positive in the high-grade areas of this case, suggesting differentiation into spindle cell RMS [ 15 ].…”

Biphenotypic Sinonasal Sarcoma With High-Grade Features: A Diagnostic Challenge

“…7 While Le Loarer et al 3 did describe a tumor with pleomorphic foci, overt highgrade features or transformation had not been characterized until recently. [4][5][6] Clinicopathological features of both reported and current BSNS tumors with high-grade areas are summarized in Table 1. There were 3 male patients and 1 female patient (age range: 66-88 years).…”

“…Two tumors presented de novo while 2 tumors showed high-grade transformation after 8 to 15 years. [4][5][6] The patients who had high-grade transformation after 15 years were initially diagnosed as synovial sarcoma and had underwent surgery followed by radiotherapy. 4 The high-grade areas of these tumors showed pleomorphism and increased mitotic count (range: 10-30/mm 2 ).…”

“…Only 3 case reports with high-grade histology have been documented previously in the literature. [4][5][6] In this article, we describe an additional patient expand the morphological spectrum of high-grade features in BSNS, and review the literature.…”

Molecular pathology in diagnosis and prognostication of head and neck tumors

“…BSS are usually low-grade tumors with frequent local recurrence, sometimes many years after diagnosis [77]. Three cases of BSS with high-grade transformation have been published [78][79][80], one of which developed into rhabdomyosarcoma (RMS). Molecular testing of BSS and RMS showed similar gene fusions including PAX3::FOXO1 and PAX3::NCOA1 [74].…”