Pseudoprogression following neoadjuvant chemoimmunotherapy for lung squamous cell carcinoma mimicking pulmonary metastatic disease on computed tomography: A case report and review of the literature.

Pseudoprogression of malignancy in patients treated with systemic immunotherapy is a well- recognised phenomenon and has also been seen in patients treated with combined chemoimmunotherapy. Neoadjuvant chemoimmunotherapy prior to surgery is a relatively new treatment strategy for the management of many malignancies. We report the case of a patient who was suspected to have primary lung squamous cell carcinoma progression following neoadjuvant chemoimmunotherapy. Tissue histopathology from biopsies demonstrated granulomatous sarcoid-like inflammation rather than progression or metastatic disease. The patient proceeded to have successful surgical clearance of residual tumour. Significantly, failure to suspect granulomatous reactions and pseudoprogression has profound influence on the trajectory of patient care, such as, the potential for patients to miss out on curative surgery. In this case report and review of the literature, we evaluate the role of pseudoprogression and the need for radiologists to be aware of this phenomenon so that they do not mistakenly report new metastases and derail the treatment paradigm for patients with curable malignant conditions.