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BackgroundPulmonary nodular lymphoid hyperplasia (PNLH) is a non-neoplastic pulmonary lymphoid disorder that can be mistaken for malignancy on radiography. Herein, we present nine cases of PNLH, emphasizing clinicoradiological findings and histological features. MethodsWe analyzed radiological and clinicopathological features from the electronic medical records of nine patients (eight females and one male) diagnosed with PNLH. IgG and IgG4 immunohistochemical staining was performed in three patients. ResultsTwo of the nine patients had experienced tuberculosis 40 and 30 years prior, respectively. Interestingly, none were current smokers, although two were ex-smokers. Three patients complaining of persistent cough underwent computed tomography of the chest. PNLH was incidentally discovered in five patients during examination for other reasons. The remaining patient was diagnosed with the disease following treatment for pneumonia. Imaging studies revealed consolidation or a mass-like lesion in eight patients. First impressions included invasive adenocarcinoma and mucosal-associated lymphoid tissue‒type lymphoma. Aspergillosis was suspected in the remaining patient based on radiological images. Resection was performed in all patients. Microscopically, the lesions consisted of nodular proliferation of reactive germinal centers accompanied by infiltration of neutrophils and macrophages in various degrees and surrounding fibrosis. Ultimately, all nine patients were diagnosed with PNLH and showed no evidence of recurrence on follow-up. ConclusionsPNLH is an uncommon but distinct entity with a benign nature, and understanding the radiological and clinicopathological characteristics of PNLH is important.

Background:Cytologic diagnosis of pulmonary adenoid cystic carcinoma (AdCC) is frequently challenging and differential diagnosis with small cell carcinoma is often difficult.Methods:Eleven cytologically diagnosed cases of pulmonary AdCC were collected and reviewed according to fifteen cytomorphologic characteristics: small cell size, cellular uniformity, coarse chromatin, hyperchromasia, distinct nucleolus, frequent nuclear molding, granular cytoplasm, organoid cluster, sheet formation, irregular border of cluster, hyaline globule, hyaline basement membrane material, individual cell necrosis or apoptotic body, and necrotic background. Twenty cases of small cell carcinoma and fifteen cases of non-pulmonary AdCC were also reviewed for the comparison.Results:Statistically significant differences were identified between pulmonary AdCC and small cell carcinoma in fourteen of the fifteen cytomorphologic criteria (differences in sheet formation were not statistically significant). Cellular uniformity, distinct nucleolus, granular cytoplasm, distinct cell border, organoid cluster, hyaline globule, and hyaline basement membrane material were characteristic features of AdCC. Frequent nuclear molding, individual cell necrosis, and necrotic background were almost exclusively identified in small cell carcinoma. Although coarse chromatin and irregular cluster border were observed in both, they favored the diagnosis of small cell carcinoma. Hyaline globules were more frequently seen in non-pulmonary AdCC cases.Conclusions:Using the fifteen cytomorphologic criteria described by this study, pulmonary AdCC could be successfully distinguished from small cell carcinoma. Such a comprehensive approach to an individual case is recommended for the cytologic diagnosis of pulmonary AdCC.