Microscopic Description -- Right Lower Lobe Pulmonary Mass


The right upper lobe nodule demonstrated a highly cellular lesion (Figure 1) composed of a monomorphic population of Cd1a positive (Figure 2), S100 positive (Figure 3), CD68 negative histiocytes admixed with a few neutrophils, eosinophils, and lymphocytes. Few atypical mitotic figures were evident. Sections of the right lower lobe mass revealed a moderately differentiated adenocarcinoma (Figure 4) with clear cell features (Figure 5) and focal necrosis. Immunohistochemical evaluation of this mass demonstrated strong positivity for CK7 (Figure 6), focal positivity for TTF, and negativity for CK20.


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