Rare Low-Grade Sinonasal Cancer Diagnosed After Gum Mass and Loose Tooth

A 50-year-old man who sought care for a mass in his left upper gum and loosening teeth turned out to have a rare malignant tumor hiding in his maxillary sinus, according to a case report published in Discover Oncology. The tumor, low-grade sinonasal adenocarcinoma of the non-intestinal type (LG non-ITAC), presented without any nasal symptoms, and the report’s authors argue that such misleading presentations make accurate clinicopathologic diagnosis genuinely difficult.

LG non-ITAC is a rare malignant epithelial tumor of the sinonasal tract. Its clinical and radiologic manifestations are often non-specific, and its histologic features can overlap with benign sinonasal glandular lesions and other low-grade adenocarcinomas. Because diagnosis directly affects surgical management, prognosis assessment and long-term surveillance, the authors stress that getting it right matters clinically. Tumors arising in the maxillary sinus are uncommon and may present with symptoms that obscure their sinonasal origin, which is exactly what happened in this case.

Computed tomography showed a destructive lesion centered in the left maxillary sinus. Histologic examination revealed back-to-back glands, tubules and papillary structures with scant intervening stroma. The tumor cells were relatively uniform, with round-to-oval nuclei and eosinophilic cytoplasm. Focal necrosis was present, and the tumor showed 4 mitoses per 10 high-power fields.

An extensive immunohistochemistry panel helped define the tumor’s profile. The cells were positive for pancytokeratin (AE1/AE3) and CK7, with CK5/6 staining in occasional tumor cells and focal weak androgen receptor positivity. Notably, HER2 immunohistochemistry scored 3+. Negative markers included CK20, CDX2, SATB2, Villin, MUC2, Calponin, DOG1, mammaglobin, p40, p63, pan-TRK, S100, SMA and SOX10. The Ki-67 labeling index was approximately 40%, and tumor-cell p53 nuclear staining was absent.

Molecular testing added further definition. Fluorescence in situ hybridization detected no NTRK3 or EWSR1 rearrangements and no ETV6::NTRK3 fusion. Taken together, the findings led to the tumor being classified as low-grade non-ITAC, a diagnosis the authors emphasize was challenging to reach given the tumor’s unusual presentation and its histologic resemblance to other glandular lesions of the region.

Treatment consisted of surgery. The patient underwent left subtotal maxillectomy, resection of adjacent structures and vascularized flap reconstruction. No postoperative radiotherapy or chemotherapy was given. He then remained recurrence-free for five years.

The story did not end there. In the sixth postoperative year, a recurrence at the skull base was detected. That lesion was resected at another hospital and reported as recurrent non-ITAC.

Beyond the individual case, the report carries a practical message for clinicians: a gingival mass with tooth mobility may be the presenting manifestation of maxillary sinus LG non-ITAC.

The report is published as an open-access case report, and the version shared at publication is an early, citable accepted manuscript carrying a permanent DOI, subject to further edits before the final version of record. As a single-patient case report, it documents one diagnostic pathway and outcome rather than establishing general treatment efficacy, but it illustrates the diagnostic workup, the surgical approach and the surveillance timeline for this rare tumor in detail.

Subject of Research: Diagnosis and long-term follow-up of low-grade non-intestinal type sinonasal adenocarcinoma of the maxillary sinus

Article Title: Low-grade sinonasal adenocarcinoma non-intestinal type of the maxillary sinus presents challenges for clinicopathologic diagnosis in a case report

Article References: Chen, Z.-P., Yu, J.-L., Chen, X.-Y., Xie, N., Chen, X.-H., Li, X.-C., Lin, H., Xia, J., & Xu, M. (2026). Low-grade sinonasal adenocarcinoma non-intestinal type of the maxillary sinus presents challenges for clinicopathologic diagnosis in a case report. Discover Oncology. https://doi.org/10.1007/s12672-026-06178-4

Image Credits: AI Generated

DOI: 10.1007/s12672-026-06178-4

Keywords: sinonasal adenocarcinoma, maxillary sinus, case report, immunohistochemistry, HER2, skull-base recurrence, head and neck oncology, differential diagnosis, long-term surveillance, maxillectomy, Low-grade, sinonasal