Partial response in non-resectable adenosquamous carcinoma of the pancreas with high tumour mutation burden treated with gemcitabine, nab-paclitaxel and pembrolizumab.

A previously healthy man in his 60s was diagnosed with a rare histological subtype of pancreatic cancer, adenosquamous carcinoma. After somatic mutation profiling, it was found that the tumour had microsatellite instability status high and a high tumour mutational burden. The patient was started on combination therapy with gemcitabine, nab-paclitaxel and pembrolizumab. Tumour size and biomarkers showed a dramatic response eventually leading to the patient being transitioned to maintenance therapy with pembrolizumab. The patient has demonstrated continued response since the start of the treatment. This is the first report in the literature showing a sustained response in this type of neoplasm that was treated with a checkpoint inhibitor, and thus adds to the evidence supporting universal somatic testing in all pancreatic cancers for a tailored approach to therapy.

Primary Undifferentiated Neoplasm of the Left Arm with Characteristics of Extragonadal Germ Cell Tumor and High-Grade Sarcoma.

A previously healthy man in his late 20s was diagnosed with a primary undifferentiated non- metastatic tumor of the left arm. After a biopsy, a clear pathological diagnosis could not be established. The tumor had positive immunohistological markers for both an extragonadal germ cell tumor and a high-grade sarcoma. Given the presumed germ cell etiology, he was started on empiric chemotherapy with etoposide and cisplatin. After a few cycles, the tumor showed dramatic response. However, due to poor patient follow- up, it progressed to massive size with severe compromise of the joint and critical neurovascular structures, which led to the decision for limb amputation. Post-surgical checkups showed no recurrence of the primary tumor or metastasis. This is the first report in the literature showing a tumor with these histological characteristics that responded to platinum-based therapy. It provides evidence for the need of more specific markers for the pathological evaluation of undifferentiated neoplasms.