Sinonasal Leiomyosarcoma: Case Report of a Rare Entity

Background: Leiomyosarcoma (LMS) is an uncommon yet aggressive malignant tumor with smooth muscle differentiation, classically found in the uterus, retroperitoneum, and digestive tract. Approximately 3% of LMS are found in the head and neck and even more rarely in the sinonasal tract. Fewer than 100 cases have been reported, mostly as single case reports. Here, we present a patient with sinonasal LMS originating from the lateral nasal wall.

Case Presentation: A 69-year-old male initially presented with 6 to 7 months of right-sided nasal obstruction, unresponsive to antibiotics and nasal sprays. A mass was noted in the right nasal cavity. Biopsy was positive for malignancy and suggestive of sarcoma versus sarcomatoid carcinoma. CT and MRI demonstrated a large homogeneous mass, 7 cm in greatest dimension, filling the right nasal cavity with erosion of the skull base, and orbit without evidence of dural, orbital fat, or extraocular muscle involvement. PET CT demonstrated a hypermetabolic mass with peak observed SUV value of 5.2 and was negative for metastases. The patient was referred to our institution for further management.

Treatment: The patient underwent endoscopic resection. Intraoperatively, the tumor filled the nasal cavity out to the nasal vestibule. Centripetal dissection revealed an attachment point to the lateral nasal wall along the inferior turbinate, which was infiltrated with tumor. The bone of the orbital wall and skull base that appeared demineralized on CT scan was not grossly invaded and the overlying mucosa was negative for tumor on frozen section. A medial maxillectomy and pterygopalatine fossa dissection was performed. Frozen sections assisted in achieving negative margins from all areas of concern.

Pathology: The majority of the tumor consisted of high-grade pleomorphic cells with punctate coagulative necrosis and up to 8 mitoses per 10 high power fields. Also, <10% of the tumor was of lower grade with residual smooth muscle morphology. Immunohistochemistry was positive for smooth muscle markers (Desmin, Caldesmon, and SMA). K_i-67 proliferative index in the pleomorphic areas was increased (30%). These findings were consistent with leiomyosarcoma. There was infiltrative growth, including around vessels and as single cells beyond the tumor border. Based on the size of the tumor, the stage was pT3.

Outcome and Follow-up: Given the patient's clinical and histologic findings, our multidisciplinary tumor board recommended adjuvant radiation therapy to improve local control of the disease. The patient is doing well 2 months of postoperatively and currently undergoing radiation therapy.

Discussion: Sinonasal LMS is extremely rare. Patients with sinonasal LMS often present late due to a lack of specific clinical and radiographic findings. Histopathology is crucial in diagnosis. The primary treatment modality is surgical resection followed by adjuvant radiotherapy and/or chemotherapy in patients with locally advanced or metastatic disease.

Fig. 1 CT of right nasal cavity lesion with erosion of orbit and skull base. CT, computed tomography.

Fig. 2 T1 postcontrast MRI of right nasal cavity lesion without invasion of dura or orbital fat/muscle. MRI, magnetic resonance imaging.

Fig. 3 Pathology findings were consistent with leiomyosarcoma.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
12 February 2021