Acrometastasis from an epidermal-growth-factor-receptor (EGFR) mutation-positive lung adenocarcinoma

We report the first case of epidermal-growth-factor-receptor (EGFR) mutation-positive lung adenocarcinoma with acrometastasis in a 51-year-old woman who presented with a swelling on her right hand. Magnetic resonance imaging revealed an expansile lesion at the base of the 5th metacarpal bone of her right hand with cortical erosion and patchy enhancement suggestive of a malignant transformation of a giant-cell tumor. A core needle biopsy of this lesion showed a metastatic adenocarcinoma on histopathological examination which was immunoreactive to cytokeratin (CK) 7 and thyroid transcription factor (TTF)-1 but not to CK20 suggesting a lung primary. A chest radiograph and computed tomography (CT) scan revealed a right upper lobe lung mass. Fluoro-deoxyglucose hypermetabolism was noted in the lung mass and the right 5th metacarpal bone lesion but not elsewhere on positron-emission-tomography/CT scan. Needle biopsy of the lung mass showed adenocarcinoma with histopathological and immunohistochemical features similar to that of the right 5th metacarpal bone lesion. Both the primary lung adenocarcinoma and the acrometastatic lesion were tested positive for EGFR mutation in exon 21 (L858R substitution). She underwent R0 resection of her right upper and middle lobes with systematic mediastinal lymph nodes resection and wide excision of the metacarpal metastasis followed by cytotoxic chemotherapy. A curative approach with complete resection of the primary tumor and oligometastastic site in Stage IV non-small cell lung carcinoma (NSCLC) followed by additive cytotoxic chemotherapy has not been reported to date and as such there is still no data on disease-free survival with this approach.