PET/CT Imaging in Treatment Planning and Surveillance of Sinonasal Neoplasms

Abstract

Sinonasal cancers are uncommon malignancies with a generally unfavorable prognosis, often presenting at an advanced stage. Their high rate of recurrence supports close imaging surveillance and the utilization of functional imaging techniques. Whole-body ¹⁸F-FDG PET/CT has very high sensitivity for the diagnosis of sinonasal malignancies and can also be used as a "metabolic biopsy" in the characterization of some of the more common subgroups of these tumors, though due to overlap in uptake, histological confirmation is still needed. For certain tumor types, radiotracers, such as ¹¹C-choline, and radiolabeled somatostatin analogs, including ⁶⁸Ga-DOTATATE/DOTATOC, have proven useful in treatment planning and surveillance. Although serial scans for posttreatment surveillance allow the detection of subclinical lesions, the optimal schedule and efficacy in terms of survival are yet to be determined. Pitfalls of ¹⁸F-FDG, such as post-surgical and post-radiotherapy crusting and inflammation, may cause false-positive hypermetabolism in the absence of relapse.

Keywords: FDG; PET/CT; sinonasal malignancy; somatostatin analogs.

Figure 1

Sinonasal squamous cell carcinoma. A 49-year-old female with a history of nasal obstruction and occasional nose bleeds for a few months. The axial unenhanced CT image (a) demonstrates a left anterior nasal mass (white arrow). On corresponding coronal MRI images (b–d), the mass that is isointense relative to muscles on T1w (b) is heterogeneously hyperintense relative to muscles on fat-saturated T2w images (c), showing homogeneous enhancement on postcontrast T1w fat-saturated (d) images (white arrow). Attenuation-corrected axial (e), sagittal (f) PET, and axial (g) and coronal (h) fused PET/CT images demonstrate high FDG metabolism of the lesion (white arrow). On image (f), a surgically proven second squamous cell carcinoma focus on the left posterior nasal cavity is seen (black arrow).

Figure 2

Sinonasal involvement by lymphoma. An 84-year-old female patient with a past medical history of rheumatoid arthritis presenting with an ulcerative scalp lesion. The biopsy of the scalp lesion was consistent with EBV (+) DLBCL. Paranasal sinus CT (a) shows a right nasal cavity lesion expanding the right ostiomeatal unit and extending into the right maxillary sinus. Post-obstructive frothy secretions in the right maxillary sinus are noted. Fat-saturated coronal T2w (b) and non-fat-saturated coronal T1w (c) images better depict the primary lesion as mildly T2w hyperintense areas, whereas mucosal disease is more T2w bright. ¹⁸F-FDG PET/CT images (d) demonstrate the intense avidity of the right nasal cavity lesion as well as the scalp lesion (arrow) and two FDG-avid right pulmonary lesions.

Figure 3

Sinonasal adenocarcinoma. A 62-year-old man with a history of chronic sinus disease presenting with right-sided epistaxis. Initial CT (a–c) shows an expansile right nasal cavity mass centered in the superior/supreme meatus as well as involving the right middle turbinate. Right extraconal extension through lamina papyracea dehiscence is present. There is also dehiscence along the cribriform plate (arrow, (b)). Axial (d) and coronal (e) fused ¹⁸F-FDG PET/CT images demonstrate a hypermetabolic right ethmoid sinus mass with no evidence of lymphadenopathy or distant metastatic disease. Coronal T1w (f), T2w (g), and post-contrast T1w (h) show a heterogeneously enhanced right ethmoid sinus lesion with extraconal extension. The more anterior post-contrast T1w (i) image does not demonstrate abnormal leptomeningeal enhancement despite the underlying bone dehiscence. Subsequent pathology showed an intestinal type of adenocarcinoma with a mucinous growth pattern.

Figure 4

Nasal cavity malignant melanoma. Initial non-contrast CT images (a,b) show an expansile, destructive soft tissue lesion in the right nasal cavity, resulting in destruction of the right turbinates and ethmoid septae. The right medial maxillary sinus is dehiscent, with opacification of the right maxillary sinus. The cribriform plate is intact. Coronal fat-saturated T2w and post-contrast T1w images (c,d) show an enhancing mass primarily in the right nasal cavity without nodular dural enhancement to suggest intracranial extension. The axial non-contrast T1w image (e) shows focal areas of hyperintensity (arrow), which may represent mucinous components, melanin, or hemorrhagic content. Subsequent ¹⁸F-FDG PET/CT ((f)—axial fused, (g)—MIP) shows FDG avidity of the primary lesion without distant metastasis. A biopsy revealed malignant melanoma. The patient underwent endoscopic resection, medial maxillectomy, and total ethmoidectomy and completed radiotherapy. Follow-up CT (h) and ¹⁸F-FDG PET/CT ((i)—axial fused, (j)—MIP) show new necrotic right submandibular lymphadenopathy without sign of local recurrence at the right nasal cavity. The patient underwent a subsequent selective right neck dissection. Follow-up CT (k,l) and ¹⁸F-FDG PET/CT ((m)—axial fused, (n)—MIP) 6 months after neck dissection revealed lymphadenopathy in the right neck, including conglomerate lymphadenopathy in the submental, submandibular, and sublingual spaces and the root of the tongue.

Figure 5

Sinonasal undifferentiated carcinoma. A 42-year-old male patient presenting with progressive symptoms of postnasal drainage, nasal congestion, and facial pressure. Initial CT (a) shows an expansile right nasal cavity lesion with medial bowing of the nasal septum and lateral bowing of the maxillary sinus wall. There is soft tissue density opacification in the right maxillary sinus; however, it is not possible to discern whether this represents postobstructive opacification or lesion extension. Coronal fat-saturated T2w (d) and post-contrast T1w (g) images better delineate the lesion and postobstructive mucosal opacification. Axial CT image (b) at the level of the vidian canal shows asymmetric enlargement of the right vidian canal (arrow, (b)) with asymmetric soft tissue intensity on the non-fat-saturated axial T1w (e) image and asymmetric enhancement on the post-contrast image (h,i). The ¹⁸F-FDG PET/CT image (j) at the same level shows FDG avidity of the primary nasal cavity lesion without uptake at the right vidian canal. More caudal axial CT (c) shows erosive changes in the right pterygoid plates with erosion of the greater palatine canal (arrow, (c)). There is loss of normal fat planes in the right greater palatine canal on the axial T1w image (f), with preservation of fat in the contralateral palatine canal (arrow, (g)). The postcontrast axial image shows asymmetric enhancement in the right greater palatine canal (arrow, (h)). ¹⁸F-FDG PET/CT image (k) at the same level shows FDG uptake extending into the right greater palatine canal. Pathology was consistent with high-grade carcinoma, most consistent with sinonasal undifferentiated carcinoma.

Figure 6

Sinonasal adenoid cystic carcinoma. A 46-year-old male presenting with chronic nasal congestion that had been progressive lately. The patient underwent septoplasty without prior imaging. During surgery, a large bulk mass filling the septal bone was found. Biopsy results were consistent with adenoid cystic carcinoma. CT after septoplasty (a–d) shows an expansile, destructive soft tissue lesion in the nasal cavity, scalloping the hard palate and extending into the bilateral maxillary sinus through erosive changes in the medial maxillary sinus walls. The more posterior coronal image (c) at the sphenoid sinus level shows soft tissue thickening in the floor of the sphenoid sinus with rarefaction of the inferior wall. The axillary slice at the level of the pterygoid plate (d) shows suspicious soft tissue thickening in the left greater palatine canal (arrow). Axial and coronal fused ¹⁸F-FDG PET/CT images (e–g) show hypermetabolism in the sphenoid floor soft tissue thickening (e,g) and the nasal cavity lesion extending into the maxillary sinuses (f). Post-contrast T1w images (h,i) demonstrate homogeneous enhancement of the nasal cavity lesion extending into the maxillary sinuses (h) and sphenoid floor soft tissue thickening (i). The axial T2w image at the level of the pterygoid plate (j) confirms the CT findings and demonstrates perineural spread along the left greater palatine nerve (arrow). The more cranial T2w image at the level of the pterygopalatine fossa (k) demonstrates normal fat planes without soft tissue thickening, indicating limited perineural tumor spread radiologically.

Figure 7

Pediatric sinonasal alveolar rhabdomyosarcoma. A 9-year-old female patient presenting with persistent left nasal drainage. Initial CT (a–c) shows an infiltrative soft tissue mass originating from the left maxillary sinus and nasal cavity with erosive changes in maxillary sinus walls and extension into the left masticator space and left extra/intraconal spaces. Subsequent MRI confirms the same findings (d–f) and shows increased signal on DWI (f), indicating high cellularity. The central portion of the lesion is necrotic. ¹⁸F-FDG PET/CT (g) again shows the central necrotic changes and, in addition, shows uptake in multiple lytic axial skeleton lesions. A biopsy revealed an alveolar rhabdomyosarcoma.

Figure 8

Olfactory neuroblastoma with metastases. A 71-year-old female presenting with a palpable left neck mass. CT (a,b) demonstrated a left nasal cavity mass with dehiscence of the cribriform plate on the left side. MRI images [coronal fat-saturated T2w (c), post-contrast fat-saturated T1w (d,e)] demonstrate a T2w isointense, enhancing left nasal cavity mass invading the olfactory fossa (arrow, (d)). The biopsy of the left nasal cavity mass was consistent with grade 2 olfactory neuroblastoma. Subsequently, ⁶⁸Ga-DOTATOC PET/CT was performed. The MIP image (f) shows intense uptake in the left nasal cavity mass, with a small focus of uptake just laterally (arrow, (f)), and uptake in the left level IB and IIB lymph nodes and thyroid gland. Fused coronal (g) and axial (i) images show intense FDG uptake in the nasal cavity lesion with a small right paramidline focus of uptake at the level of the choanae (arrow (h,i)). Retrospectively, this can be identified as an enhancing focus on MRI (arrow, (e)). There is also another focus of uptake near the left orbital apex in the vicinity of the left posterior ethmoid air cells (arrow, (j,k)), which can be identified retrospectively as an area of mucosal thickening on initial CT (arrow, (b)).