To report a rare case of malignant transformation of nasal polyp into Large Cell Squamous Carcinoma, its clinical manifestations, incidence, differential diagnosis and management. A case of a 44 year old, male, with a 6 month history of nasal congestion and watery nasal discharge. Patient underwent left nasal polypectomy 12 years ago. Anterior rhinoscopy, revealed a whitish, polypoid mass obstructing the left nostril and a 3.0 x 3.0 cm, firm, fixed, non tender left maxillary mass was evident. PNS CT scan demonstrated left sino-nasal polyposis extending to the nasopharynx. Initial punch biopsy of left intranasal mass showed Squamous Cell Carcinoma, non keratinizing, poorly differentiated. Case conference consensus was a repeat biopsy revealing Undifferentiated Carcinoma, non keratinizing. Partial (antero-medial) maxillectomy was performed and final histopath revealed Large Cell Squamous Carcinoma with an area of malignant transformation of the nasal polyp. Punch biopsy was done twice and final histopathologic result revealed Large Cell Squamous carcinoma. Clinicians should submit and label all specimens and pathologists should scrutinize the smallest details seen, especially pre-malignant features. To our knowledge, this is the first documented case of nasal polyp with malignant transformation in our institution.