PMC4854032_01
Noncontrast computed tomography scan of the chest showing a 2 cm round soft tissue mass with smooth regular margin in the left lower lobe
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F1
On CT scan, the nodule displayed low attenuation and focal areas of calcification [Figure 1].
Fibrotic stromal fragment with papillary features in a background of abundant blood (Papanicolaou stain, x100)
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F2
The second pass yielded moderately cellular smears composed of scattered large fibrotic tissue fragments, some with papillary configuration [Figure 2], in a background of abundant blood.
Fibrovascular fragment associated with round cells (Diff-Quik stain, x200)
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F3
Transgressing blood vessels were evident in many of these tissue fragments [Figure 3].
Cohesive sheets of surface cells arranged in pavement-like fashion (Diff-Quik stain, x400)
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F4
They were arranged in pavement-type pattern, resembling pneumocytes and not associated with fibrovascular structures [Figure 4].
Dense collagenous stromal tissue associated with bland appearing round cells (x200)
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F5
The third pass was hypocellular and revealed some fragments of dense collagenous tissue, some associated with round cells [Figure 5].
The papillary front on the cell block lined by a single layer of flat surface cells is focally hyalinized. Scattered round cells and inflammatory cells are observed in the center of this structure (H and E, x200)
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F6
These papillary fronts were lined with a single layer of small flat or low cuboidal cells [Figure 6].
Both surface and round cells are positive for thyroid transcription factor-1 immunostain (x200)
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F7
Both surface and round tumor cells were positive for thyroid transcription factor 1 (TTF-1) [Figure 7] and negative for synaptophysin and chromogranin.
AE1/AE3 immunoreactivity is present in the surface cells but not the round cells (x200)
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F8
AE1/AE3 and negative for progesterone receptor (PR), whereas the round cells within those papillary structures were negative for AE1/AE3 and positive for PR [Figures 8 and 9]. A proliferative index marker (Ki-67) showed staining in <3% of the tumor cells.
Progesterone receptor immunoreactivity is present in the round cells but not the surface cells (x200)
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F9
AE1/AE3 and negative for progesterone receptor (PR), whereas the round cells within those papillary structures were negative for AE1/AE3 and positive for PR [Figures 8 and 9]. A proliferative index marker (Ki-67) showed staining in <3% of the tumor cells.