PART TWO
Diagnostic Cytology
Fig. 13.65 Bronchioloalveolar carcinoma, mucinous type (type I).
Pulmonary resection (H&E x LP).
Fig. 13.66 Bronchioloalveolar carcinoma, mucinous type (type I).
Pulmonary resection (H&E x MP).
pattern of growth of cylindric tumor cells along alveolar septa.299
A similar histologic pattern may be produced by adenocarcino-
mas metastatic from the stomach, pancreas, colon, and kidney,
and consequently one must exclude such tumors before an une-
quivocal diagnosis of BAC can be rendered.325 The radiographic
appearance of BAC may be that of a solitary nodule; multiple,
often bilateral nodules; or a diffuse infiltrate. Thus, except for the
solitary nodule, it may radiographically mimic metastatic cancer
in the case of bilateral nodules and pneumonitis in the case of a
diffuse infiltrate. The multinodular pattern has been attributed
to aerogenous spread of tumor cells within the lung. Two histo-
logic types of BAC have been described: a mucinous variety, char-
acterized by tall columnar cells with abundant intracellular and
extracellular mucin (type I) (see Figs 13.65 and 13.66) and a
nonmucinous type, which lacks obvious mucin production and
instead is characterized by cuboidal or columnar cells, typically
arranged along the septa in a hobnail-like fashion (type II) (see
Figs 13.67 and 13.68).312,323 By electron microscopy, the former
exhibit features of goblet cells,314,326,327 whereas the latter show
similarities to Clara cells and type II pneumocytes.314,327-333
Fig. 13.67 Bronchioloalveolar carcinoma, nonmucinous type (type II).
Pulmonary resection (H&E x LP).
Fig. 13.68 Bronchioloalveolar carcinoma, nonmucinous type (type II).
Pulmonary resection (H&E x MP).
The prognosis of adenocarcinomas, stage for stage, is worse
than that of squamous cell carcinomas,306 despite the higher rate
of resectability of the former.284,315 As a group, BACs have a bet-
ter prognosis than other adenocarcinomas320 and those patients
presenting with BACs occurring as solitary nodules fare better
than do those presenting with multiple nodules or a diffuse
infiltrate.312
The term large-cell carcinoma encompasses those primary
non-small-cell carcinomas that lack histologic evidence of either
adenomatous or squamous differentiation (Fig. 13.69).299 When
examined by electron microscopy, most cases show evidence of
differentiation, more commonly adenomatous (i.e. junctional
complexes and intercellular or intracellular lumina lined by
microvilli) than squamous;334-337 some show neuroendocrine
features,336 and the remainder lack specific findings. The subset
of large-cell carcinoma which exhibits an organoid appearance
histologically is referred to as large-cell neuroendocrine carci-
noma and is associated with a poorer prognosis than are other
large-cell carcinomas, adenocarcinomas, and squamous cell
carcinomas.338
332
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