p40, one of the two isomers of p63, is nowadays widely used for diagnosis of
squamous cell carcinoma, especially in subtyping non-
small cell carcinoma on lung biopsies. We describe a case in which lung tumour was misdiagnosed as
squamous cell carcinoma due to p40 immunopositivity. A 36-year-old lady presented with
cough and left sided
chest pain of 2 months duration. Chest imaging revealed a lesion in left lower lobe of the lung and biopsy was suggestive of
squamous cell carcinoma. However, past history revealed
amputation of great toe for non-healing discharging
ulcer which on histopathology was diagnosed as
choriocarcinoma. She also had a history of
hysterectomy five years ago, details of which were not available. Post-
amputation β-hCG levels were high and she had been treated with multimodality
chemotherapy for
choriocarcinoma. She had good response to
chemotherapy initially, however became resistant later on. Review of the lung biopsy in the light of the past history along with extensive literature review led to the final diagnosis of metastatic trophoblastic tumour to lung. Hence, awareness that p40 immunopositivity can be seen in trophoblastic tumours is essential to avoid misdiagnosis, especially in sites like the lung where
squamous cell carcinoma is common.