LAUSR

To the Editor When evaluating cytologic samples obtained using endobronchial ultrasound-guided transbronchial fine-needle aspiration (EBUS–TBNA) pathologists must be familiarized with the presence of normal structures of the bronchial wall. Bronchial columnar cells, macrophages, cartilage, mesothelial cells, and submucosal seromucinous glandular cells must not be misinterpreted as abnormal findings. This can be particularly challenging when performing rapid onsite evaluation. Oncocytic metaplasia is a common finding in submucosal bronchial glands and it is more frequent in older individuals. In most cases, oncocytic change is focal and limited to part of the glands. Rarely, oncocytic metaplasia may be more extensive and represents oncocytic hyperplasia. For the latter situation the term oncocytosis may be used. In this report, we describe a case of bronchial oncocytosis that resulted in remarkable cellular contamination of mediastinal lymph node cytological samples obtained by EBUS–TBNA. The patient, an 80-year-old man was being evaluated because of a partially cavitated pulmonary lesion in the upper left lobe and mediastinal lymphadenopathies. Bronchoscopy revealed an edematous bronchial mucosa without nodular lesions. Biopsies from the bronchial mucosa were obtained and submitted for pathologic and microbiologic studies. In addition, EBUS–TBNA of three different mediastinal lymph nodes was performed. Smears revealed a reactive lymph node population variably admixed with normal cellular elements of the bronchial wall and mucoid substance. Smears from one of the three different locations had numerous groups of oncocytic cells. These were present as monolayers and tightly cohesive groups (Figure 1). Cells were large and polygonal with well-defined cell membranes and abundant cytoplasm (Figure 2). The cytoplasm was deeply stained and sometimes finely granular. Nuclei were round, centrally located and monomorphic. The bronchial biopsy showed extensive oncocytic metaplasia of submucosal glands that created a pseudonodular hyperplastic image (Figure 3). Immunohistochemical studies were negative for synaptophysin, chromogranin, CD56, and protein S100. Despite the fact that oncocytic metaplasia of the bronchial glands is a common histologic finding it is rarely seen on cytology. The main reason is that the tracheobronchial submucosal region is usually not represented on cytologic samples. Exceptions are smears obtained by TBNA that very often contain cellular contaminants of the bronchial wall. Another reason for the absence of cytologic descriptions is that in most cases bronchial oncocytic metaplasia is focal and limited to a few submucosal glands. Although in the present case oncocytic metaplasia was unusually extensive, the pathologist must be aware of this potential cellular contaminant of TBNA samples. In our opinion, the oncocytic nature of the cells is well reflected on cytology allowing a precise recognition. The coexistence of oncocytic cellular groups with other normal cellular elements such as ciliated columnar cells, macrophages and mucoid material is an aid for its correct interpretation. Differential