Dx: Polymorphous Adenocarcinoma

That was my first conclusion until I found the area with endospores inside a spherule along with the adjacent hyphal forms with morphology of "alternating arthroconidia" (i.e. alternating ovoid, bulbous segments and straight segments). Luckily for you they're uniquely American diseases! 🙃

This is a case of Coccidioides immitis (!) infection (PCR-confirmed per treating physician request). On follow-up questioning the patient had a travel history to the southwestern US. Very easy to mistake for Blastomyces dermatitidis if all you see is the morphology in the lower left of this image.

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would love to be added too thanks!

Clinical: SoB and cough, PFTs show obstructive pattern

Rad: Air trapping/mosaic attenuation; no interstitial infiltrates

Causes: Lung or bone marrow transplant (alloimmunity), CTDs - especially RA (autoimmunity), drugs, infections, and certain fume exposures

Prognosis: Poor

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Dx: Constrictive (obliterative) bronchiolitis (CB).

Circled in blue are the hallmark lesions of CB - subepithelial fibrosis with luminal narrowing/obliteration of small airways (+/- some chronic inflammation). The alveolated lung parenchyma is essentially normal.

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history of rheumatoid arthritis and has been on a number of immunosuppressive therapies for it over the years

Didn't have access to the the images, but the report summary was "nonspecific interstitial changes with a mild apical predominance"