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Sinonasal undifferentiated carcinoma (SNUC) is an aggressive malignancy of disputed histogenesis that arises in the sinonasal tract and has an extremely poor prognosis. Despite multimodality treatment with surgical resection, radiation, and chemotherapy, recurrence is common. The tumor spreads by direct local extension, but also metastasizes to lymph nodes, brain, lung and bone. To date, reports of metastasis to the skin have not been published. We report a case of a 58-year-old woman diagnosed with SNUC who underwent surgical resection of the tumor followed by chemoradiation. The tumor soon recurred, and she required wide re-excision. Two months after this procedure, she developed multiple dermal nodules in the head and neck region, clinically suspicious for metastases. Biopsy of a nodule from the right neck revealed a poorly differentiated carcinoma, with morphological and immunohistochemical findings consistent with a metastasis of the patient's known SNUC. We conclude that the skin may be a rare site of metastasis of SNUC, and in some cases may be the presenting sign of tumor recurrence despite aggressive multimodality treatment.

Biophysical characteristics of cells are attractive as potential diagnostic markers for cancer. Transformation of cell state or phenotype and the accompanying epigenetic, nuclear, and cytoplasmic modifications lead to measureable changes in cellular architecture. We recently introduced a technique called deformability cytometry (DC) that enables rapid mechanophenotyping of single cells in suspension at rates of 1000 cells/s-a throughput that is comparable to traditional flow cytometry. We applied this technique to diagnose malignant pleural effusions, in which disseminated tumor cells can be difficult to accurately identify by traditional cytology. An algorithmic diagnostic scoring system was developed on the basis of quantitative features of two-dimensional distributions of single-cell mechanophenotypes from 119 samples. The DC scoring system classified 63% of the samples into two high-confidence regimes with 100% positive predictive value or 100% negative predictive value, and achieved an area under the curve of 0.86. This performance is suitable for a prescreening role to focus cytopathologist analysis time on a smaller fraction of difficult samples. Diagnosis of samples that present a challenge to cytology was also improved. Samples labeled as "atypical cells," which require additional time and follow-up, were classified in high-confidence regimes in 8 of 15 cases. Further, 10 of 17 cytology-negative samples corresponding to patients with concurrent cancer were correctly classified as malignant or negative, in agreement with 6-month outcomes. This study lays the groundwork for broader validation of label-free quantitative biophysical markers for clinical diagnoses of cancer and inflammation, which could help to reduce laboratory workload and improve clinical decision-making.