Unusual dual malignancy: basaloid squamous cell carcinoma arising from inverted papilloma with contralateral temporal bone carcinoma.

A rare case of dual malignancy involving sinonasal basaloid squamous cell carcinoma (BSCC) and contralateral temporal bone carcinoma is presented in a female patient in her early 50s. With a prior history of sinonasal inverted papilloma excision 3 and 5 years earlier, she presented with nasal obstruction, forehead swelling and left ear symptoms. Imaging revealed aggressive sinonasal and temporal bone masses with intracranial and orbital involvement. The patient underwent surgical resection of the sinonasal tumour and biopsy of the temporal bone lesion. Histopathology confirmed BSCC (basaloid squamous cell carcinoma) in the sinonasal mass and non-keratinising squamous cell carcinoma in the temporal bone. Despite planned adjuvant chemoradiotherapy, rapid recurrence occurred, leading to death within 3 months. This case highlights the aggressive nature of BSCC, the possibility of malignant transformation from inverted papilloma, and the importance of thorough histopathological evaluation and multidisciplinary management in complex sinonasal malignancies.