Cavitary Lung Lesions From Metastatic Colorectal Adenocarcinoma

To the Editor: CASE A 60-year-old female was referred to the pulmonary medicine clinic for workup of cystic and nodular lung disease. The patient had no symptoms to suggest a systemic infection, no history of lung disease in the past, and reported unremarkable chest x-ray before the recent illness. Four months before presentation, the patient presented to her physician for cough, prompting a workup for tuberculosis which included sputum acid-fast bacilli, bronchoscopy with bronchoalveolar lavage and acid-fast bacilli, and T-spot. Lung computed tomography (CT) scan revealed innumerable cysts with calcifications (Figs. 1A–C). The patient was isolated and treated with antimycobacterial therapy for 3 months before a repeat bronchoscopy with transbronchial biopsies confirmed the presence of metastatic mucinous adenocarcinoma. Shortly after, she presented with intestinal obstruction and underwent right colectomy with side to side ileocolonic anastomosis and partial omentectomy. Pathology revealed an invasive mucinous adenocarcinoma arising in a tubulovillous adenoma forming a 5.0-cm circumferential mass. A solid tumor genomic assay found KRAS and G12C mutations.FIGURE 1: A, Computed tomography (CT) chest axial view lung window depicting multiple cystic lung lesions. B, CT chest axial view mediastinal window depicting multiple cystic lung lesions. C, CT chest lung window coronal view multiple cystic lung lesions.On initial presentation to the pulmonary clinic, repeat chest CT showed innumerable pulmonary cavities measuring up to 2.2×1.1 cm through. A positron emission tomography-CT followed, finding enlarged pericecal lymph nodes, innumerable cystic and solid bilateral pulmonary nodules mildly fluorodeoxyglucose avid, retroperitoneal, mediastinal, and hilar lymphadenopathy, and thoracic vertebral, manubrium and seventh rib lesions. Because there was no index of suspicion for further workup for infectious etiologies, chemotherapy was started for metastatic colon cancer. DISCUSSION The most frequent etiologies of cavitary lesions are an abscess, cavitary tumors, mycobacterial and fungal infections.1 Cavitating lesions are present in only 4% of metastatic nodules and 70% of those are due to metastatic squamous cell carcinoma.2–4 Typically, lung metastases of adenocarcinoma from the intestinal tract present as consolidation. Metastatic mucinous adenocarcinoma has previously been noted in the liver.5 Cystic lung lesion etiologies, in contrast, include pulmonary Langerhans cell histiocytosis, interstitial pneumonia, congenital cystic lung disease (bronchogenic cysts), and systemic disease (amyloidosis, neurofibromatosis type 1).6 Misdiagnosis of metastatic lung adenocarcinoma as the pulmonary infection has a prevalence of 10% in the literature due to the absence of symptoms, prompting a delay in treatment.1 A primary lung malignancy with multiple metachronous lesions, in this context, are much less likely given the patient’s presentation and past medical history.7 CONCLUSIONS The aim of this brief case presentation is to alert clinicians to look for unusual features of pulmonary metastases due to colonic adenocarcinoma. Aditya Srinivasan, MSc* Horiana B. Grosu, MD†‡*Department of Internal Medicine University of Texas Health Science Center at Houston Departments of†Pulmonary Medicine‡Cytology, The University of Texas MD Anderson Cancer Center, Houston, TX