Micropapillary Mucinous Adenocarcinoma of the Lung: A Brief Case Report
A 69-year-old woman presented with persistent cough for one month previously. The patient had a 13 pack-year smoking history and hypertension. Chest computed tomography revealed predominant ground glass opacity with patchy consolidation occupying almost the entire left lower lobe of the lung (). It was histologically confirmed as adenocarcinoma of the lung by transbronchial lung and lymph node biopsy. Analysis of EGFR and K-ras mutation by polymerase chain reaction-sequencing was performed on tissue from the lymph node biopsy, which revealed missense mutation of K-ras in the 12th codon, c.34G>T (p.G12C), without EGFR mutation. After neoadjuvant concurrent chemoradiation, a left lower lobectomy was performed. The gross examination revealed a poorly defined, large, mass-like lesion with scattered dilated bronchus, which was similar in appearance to lobar pneumonia and well correlated with radiologic findings ().\nMicroscopically, the tumor demonstrated a predominantly micropapillary growth pattern in the alveolar cavity and a lepidic growth pattern along the septa with hobnail features (). Neoplastic cells with abundant clear or amphophilic cytoplasm intermingled with each other (). Special stains (periodic acid Schiff, mucicarmine, and Alcian blue pH 1.0 and 2.5) revealed positivity in the cytoplasm of a few tumor cells (, inset). Tumor cells had well-defined cell borders and large, pleomorphic nuclei (), with occasional horse-shoe shaped nuclei and perinuclear clearing. Their nuclei had a contorted prominent membrane, similar to the raisinoid appearance induced by human papillomavirus infection, and had frequent prominent macronucleoli ().\nNo complications were noted in the two-month follow-up period after discharge.