PMC9720315_01
Chest computed tomography shows (A) a nodulous shadow located in the segmentum basale laterale of the right lower lobe measuring 2.6 cm x 1.8 cm in size with a smooth margin and (B) soft tissue density.
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Three years later, computed tomography presented a 2.6-cm x 1.8-cm mass with soft tissue density and smooth margin in the lateral basal segment of the right lower lobe ( Figure 1 ).
Pathological findings of the tumor show two distinct histological subtypes. (A) H&E of the whole slide scan showing the well-defined tumor located in the dilated bronchus or bronchiole and (B) focally connecting to the normal bronchial walls. (C) Lower power H&E (x4) reveals two distinctly demarcated tumor cell populations (red arrow: epithelial component; blue arrow: mesenchymal component). (D) High power H&E (x40) reveals that the two components grow closely to each other, but without a transitional zone (line). (E) H&E (x40) of the mixed squamous cell and glandular papilloma (red arrow: glandular component; blue arrow: squamous cell component). (F) H&E (x40) of the glomus tumor component.
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Microscopically, the tumor was a conspicuous endobronchiolar growth within the dilated bronchus or bronchiole ( Figures 2A, B , whole slide scan). The tumor showed a well-demarcated border, which was connected to the normal bronchial walls in some areas ( Figure 2B ). At low magnification, the tumor was composed of two different histological components, including MSGP and GT ( Figure 2C ). Although the two kinds of tumor cells were close to each other, a distinct demarcation between them could still be found, there were no intertwined components, and a transitional morphology existed in the neighboring cell populations ( Figure 2D ). The glandular epithelium was composed of a mixture of ciliated or non-ciliated columnar cells, mucous columnar cells, and scattered goblet cells ( Figure 2E ). The uniform tumor cells were small and round, with inconspicuous nucleoli, lightly eosinophilic cytoplasm, and sharply defined cell margins ( Figure 2F ).
Immunohistochemical results of the pulmonary collision tumor. Epithelial element stains were positive for (A) CK5/6, (B) P63, (C) P40, and (D) CK7 but negative for (E) TTF-1. (F) Ki-67 was positive on the basal side of the areas of squamous epithelial, approximately 1%-2%. Mesenchymal element stains were diffusely positive for (G) collagen IV and (H) MSA. (I) The percentage of Ki-67 expression in the area of glomus tumor cells was less than 1%.
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Immunohistochemically, the squamous component of MSGP was positive for CK5/6, P63, and P40, and the glandular component of MSGP was positive for CK7 ( Figures 3A-D ). Both components were positive for AE1/AE3 and negative for thyroid transcription factor-1 (TTF-1) ( Figure 3E ) and napsin A. Ki-67 was positive on the basal side of the areas of squamous epithelial ( Figure 3F ). GT was diffusely positive for collagen IV ( Figure 3G ) and muscle-specific actin (MSA) ( Figure 3H ), focally positive for alpha-smooth muscle actin (alpha-SMA), weakly positive for CD56, and negative for caldesmon, calponin, CD34, ERG, and STAT6. The Ki-67 index was less than 1% ( Figure 3I ).