B-cell Lymphoblastic Lymphoma Presenting as a Sinonasal Mass: A Case Report.

B-cell lymphoblastic lymphoma (B-LBL) is an abnormal proliferation of lymphocyte precursor cells located primarily outside of the bone marrow and peripheral blood, typically in the mediastinum or other lymph nodes. It is often a disease of childhood that presents with lymphadenopathy, fatigue, pallor, bone pain, and weight loss with laboratory findings of anemia and thrombocytopenia. Initial presentations prompted by head and neck manifestations are exceedingly rare. A five-year-old girl with no significant past medical history presented with right facial swelling and mild proptosis on ophthalmologic evaluation. She was referred to a tertiary care facility by her local otolaryngologist for further management after computed tomographic imaging revealed right maxillary sinus opacification and erosion of the anterior maxillary bone. Her symptoms were initially responsive to prednisone and amoxicillin-clavulanate, and only right unilateral nasal discharge persisted with a near-complete resolution of other sinonasal symptoms. Notably, laboratory values, including complete blood count, were within normal limits. Given concern for the etiology of the bony erosion, the patient presented for a second opinion, where imaging and biopsy resulted in flow cytometry findings consistent with B-ALL/LBL. After a bone marrow biopsy, the ultimate diagnosis was Murphy's stage III B-cell lymphoblastic lymphoma. Malignant neoplasms of the sinonasal region are rare in children, where primary sinonasal B-LBL is a unique occurrence. Clinical features of sinonasal B-LBL in the paranasal sinuses may masquerade as pathologies such as acute sinusitis, orbital cellulitis, and benign tumors or polyps that can lead to a confounding diagnosis. In this case presentation, an initial response to steroids and antibiotics should not provide false reassurance when other features and signs, such as maxillary bone erosion, may suggest the presence of malignancy.