Fig. 4
a Morphologic and cytologic features of metastatic pulmonary adenocarcinoma in pleural biopsy and concurrent pleural effusion. Small papillary clusters of neoplastic cells lacking a fibrovascular core. Pleural biopsy. Hematoxylin and eosin. ×60. b Nest of neoplastic cells growing in a “paving stone” fashion. Pleural biopsy. Hematoxylin and eosin. ×60. c Irregular glandular structures lined by neoplastic cells. Pleural biopsy. Hematoxylin and eosin. ×60. d Corresponding effusion showing a micropapillary-like architecture (tight small clusters of cells with predominantly eccentric nuclei). ×60. Pap, cytospin.