Contributed by Alicia M. Hunt, MD, and Sanja Dacic, MD, PhD
The patient is a 65-year-old female with a history of exposure to tuberculosis who had an incidental lung mass - A CT chest showed a 5 cm heterogeneous solid-appearing mass along the medial margin of the right lower lobe of the lung. Radiology was unable to definitively state the origin of the mass, but suggested pleural or mediastinal origin. The mass was moderately PET avid, and the patient was scheduled for an FNA of the mass. The FNA with cell block preparation showed a reactive inflammatory process with chronic inflammation, fibrosis, and hemosiderin deposition. The patient was referred for surgery due to vague complaints of chest pain, and upon exploration, the mass was found to be intraparenchymal in the right lower lobe. It was well-encapsulated, but intimately associated with the inferior pulmonary vein. The mass was enucleated and sent for intraoperative consultation.
The mass was received attached to a small wedge of lung and measured 5.0 x 4.0 x 3.0 cm. On cut surface, the mass was soft, tan, and dark brown with foci of hemorrhage (Figure 1).
HISTOLOGICAL AND IMMUNOHISTOCHEMICAL FINDINGS
Histological sections demonstrated a well circumscribed, but not encapsulated neoplasm composed of several different growth patterns including papillary, sclerotic, solid, and hemorrhagic (Figures 2, 3, 4 and 5). A dual population of neoplastic cells was easily identified: cuboidal "surface cells" resembling type II pneumocytes and stromal "round cells". The papillary areas had fibrovascular cores lined by cuboidal surface cells and containing round stromal cells (Figures 6 and 7). The hemorrhagic areas contained large blood-filled spaces, hemosiderin and cholesterol clefts with multinucleated giant cells (Figure 8). Solid areas had sheets of round cells focally forming small tubules that are variably surrounded by dense hyalinized collagen. The two cell types showed a slightly different immunoprofile. The stromal and surface cells were positive for TTF-1 and EMA. Unlike stromal cells, the surface cells were positive for surfactant apoprotein A, pankeratin, and cytokeratin 7. Occasional stromal cells were positive for estrogen receptor and progesterone receptor (Figure 9).