PMC6204234_01
Area of respiratory lining epithelium with squamous metaplastic change (arrowheads).
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fig1
Histological examination revealed fragments of respiratory-type epithelium with focal cystic invagination and associated squamous metaplasia [Figure 1].
Focal areas of stroma displaying hyalinization (arrowheads).
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fig2
The underlying stroma consisted of a variably cellular, benign spindle cell proliferation with an associated background of hyalinization [Figure 2], calcification and ossification [Figure 3], and focal chondroid change [Figure 4] in a vague lobule-like arrangement.
Focal areas displaying calcification and ossification surrounded by variably spindled stroma.
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fig3
The underlying stroma consisted of a variably cellular, benign spindle cell proliferation with an associated background of hyalinization [Figure 2], calcification and ossification [Figure 3], and focal chondroid change [Figure 4] in a vague lobule-like arrangement.
Chondroid regions which support the hamartomatous nature of the lesion. Inset shows area at low-power with spatial relation of components, including surface ciliated epithelium (*) and bone (within dashed lines).
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fig4
The underlying stroma consisted of a variably cellular, benign spindle cell proliferation with an associated background of hyalinization [Figure 2], calcification and ossification [Figure 3], and focal chondroid change [Figure 4] in a vague lobule-like arrangement.
Variably dilated cystic regions within the lesion.
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fig5
Focal areas of aneurysmal and cystic changes [Figure 5] were seen which would provide an explanation for the clinically noted enlargement since hamartomas by definition would be expected to have a much lower rate of growth.
Disorganized bundles of nervous tissue interspersed within collagenous stroma.
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fig6
Areas with haphazard arrangement of nerve bundles within the collagenous stroma [Figure 6] were also noted.
Immunohistochemistry for smooth muscle actin (SMA) showing positive staining in the spindled lesional cells.
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fig7
Immunohistochemical stains were positive for SMA [Figures 7(a) and 7(b)] in the spindle cells and negative for CK AE1/AE3, EMA, CD34, Stat6, ERG/FLI-1, Mucin 4, S-100, Sox-10, and desmin [Figure 8]; ruling out perineurioma, solitary fibrous tumor, a vascular neoplasm, Evans tumor, a benign peripheral nerve sheath tumor, or a myogenic neoplasm.
Lesional cells are negative for pan-cytokeratin (ae1/ae3), desmin, Sox-10, and S100. CD34 and ERG/FLI-1 highlight vascular endothelial cells.
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fig8
Immunohistochemical stains were positive for SMA [Figures 7(a) and 7(b)] in the spindle cells and negative for CK AE1/AE3, EMA, CD34, Stat6, ERG/FLI-1, Mucin 4, S-100, Sox-10, and desmin [Figure 8]; ruling out perineurioma, solitary fibrous tumor, a vascular neoplasm, Evans tumor, a benign peripheral nerve sheath tumor, or a myogenic neoplasm.