Solitary Tracheobronchial Papilloma: Cytomorphology and ancillary studies with histologic correlation

Abstract

Solitary tracheobronchial papilloma (STBP) is a rare benign tumor that primarily involves the tracheobronchial tree. Human papilloma virus (HPV) infection is associated with dysplasia and a high risk of carcinoma in these lesions. The cytomorphology of STBP is not well established in the literature. Our aim is to characterize the cytomorphologic features of STBP, with histologic correlation in a series of 6 patients - 4 males and 2 females - with a mean age of 67 years (range, 53-88 years). There were 5 biopsy-proven squamous papillomas and 1 glandular papilloma. On surgical biopsy, squamous papillomas exhibited cytological atypia (4 graded mild and 1 graded moderate with focal severe dysplasia), surface erosion, and inflammation. Cytology specimens available for review included a combination of 4 fine-needle aspirations (FNAs), 2 bronchoalveolar lavages and 2 (of 3) bronchial brushings. Cytologic findings associated with squamous papillomas included atypical squamous cells and rare squamous cell resembling koilocyte in 1 bronchial brushing. Sheets of squamous cells were identified in another specimen. Several cases had a prominent background of acute inflammation, and candida was present in 1 specimen. HPV in-situ hybridization was positive in 1 case and negative in 2 cases. A p16 immunocytochemical stain performed on 1 cell block was negative. In conclusion, although STBP is a rare neoplasm, these cases may be encountered in respiratory cytology samples. FNA of papillomas yields fewer lesional cells compared to exfoliative samples. These lesions may be mistaken in cytology specimens for squamous cell carcinoma, squamous-lined cavitary lesions, an infectious (fungal) process, reactive squamous metaplasia, or oral contamination.

Keywords: Cytology; dysplasia; human papilloma virus (HPV); lung; papilloma; solitary tracheobronchial papilloma.

Figure 1

Cytomorphology of solitary tracheobronchial papillomas; a) Atypical squamous cells present in a background of neutrophils (Case 1, ×40 magnification; Pap stain smear), with atypical squamous cell (inset, ×60 magnification); b) Squamous cell resembling a koilocyte identified in a bronchial brushing specimen (Case 1, ×40 magnification; Pap stain, ThinPrep); c) Ball of squamous cells seen on ThinPrep (Case 6, ×40 magnification; Pap stain, ThinPrep); d) Sheet of squamous cells seen in cell block (Case 6, ×10 magnification; H and E stain, cell block)

Figure 2

Histopathology of solitary tracheobronchial papillomas; a) Papilloma lined by squamous epithelium (Case 5, ×10 magnification; H and E stain); b) Papilloma lined by glandular epithelium (Case 3, ×10 magnification; H and E stain), with ciliated columnar cells (inset, ×40 magnification); c) Squamous epithelium with low-grade dysplasia (Case 5, ×20 magnification; H and E stain); d) Squamous epithelium with high-grade dysplasia (Case 1, ×40 magnification; H and E stain)

Figure 3

a) Histopathology of squamous epithelium showing koilocytes (Case 1, ×40 magnification; H and E stain); b) HPV in-situ hybridization in a squamous papilloma with dysplasia, showing focal nuclear positivity (Case 1, ×40 magnification; p16INK4, MTM lab)