ferentiated squamous caricnoma of the bron-

chus 18 examples of this tumour were

studied. On light microscopy i0 of the

tumours contained loci of keratinisation or

intercellular bridges and therefore ful-

filled the World Health Organisation's diag-

nostic criteria. In eight these features

were absent, but the overall appearance was

sufficiently squamoid to preclude their

placement in any other category. On electron

microscopy many cells showed the charac-

teristic desmosomes and tonofilaments of

s~mous carcinoma, but there were also

areas of adenodifferentiation. The

ultrastructure of both light microscopic

groups was identical. In conclusion, this

type of tumour is dimorphic with charac-

teristics of adenocarcinoma and squamous

carcinoma on electron microscopy.

Keratinisation and bridges are not essential

diagnostic criteria: the overall pattern and

cellular morphology are more important.

Subtypes of Small Cell Carcinoma of the

Lung: Morphometric, Ultrastructural, and Im-

munohistochemical Analyses.

Nomori, H., Shimosato, Y., Kodama, T. et al.

Pathology Division, National Cancer Center

Research Institute, Chuo-ku, Tokyo 104,

Japan. Hum. Pathol. 17: 604-613, 1986.

Fifty-three surgically resected small

cell carcinomas of the lung were studied

morphometrically, electron microscopically,

in~mlnohistochemically, and in terms of pos-

sible site of origin. Four subtypes of small

cell carcinomas were identified: oat cell

carcinoma (OAT), small cell carcinoma of the

intermediate cell type (INT), combined oat

cell carcinoma, and undifferentiated car-

cinoma of the small cell type (UCS). The

latter type is presumed to be nonneuroen-

docrine. Morphometric analysis showed con-

siderable overlap among OAT, INT, and UCS

with respect to nuclear area, cell area, and

nuclear/cytoplasmic ratio. Ultrastruc-

turally, significantly more carcinomas

categorized as OAT and INT contained

neurosecretory granules than did those in

the UCS category (P<O.01 and 0.05,

respectively). Cells with tonofibrils were

more frequent in UCSs than in OATs and INTs.

Inm~mohistochemically, fewer UCSs than OATs

contained cells with gastrin-releasing pep-

tide, neuron-specific enolase, and Leu-7 (P

= 0.5, P<0.05, P<0.05, respectively). UCSs

were located more frequently at the

periphery of the lung than were OATs

33

(P<O.OI)) and INTs (P = 0.06). These find-

ings suggest that UCS may be a pathologic

entity distinct from the typical

neuroendocrine-type small cell carcinoma and

that this subtype probably corresponds to

small cell carcinoma with a 'large cell com-

ponent,' and to very poorly differentiated

adenocarcinoma and sqlmmous cell carcinoma

of the small cell type.

Mixed Small Cell and Non-Small Cell Lung

Cancer.

Adelstein, D.J., Tomashefski, J.F. Jr.,

Snow, N.J. et al. Department of Medicine,

Cleveland Metropolitan General Hospital,

Cleveland, OH 44109, U.S.A. Chest 89: 699-

704, 1986.

Seventeen (i0 percent) of 176 patients

with small-cell carcinoma of the lung seen

at this hospital since 1976 proved to have

mixed small-cell and non-small-cell tumors.

The presence of a mixed lung cancer was es-

tablished prior to chemotherapy or irradia-

tion in nine patients. Eight were initially

diagnosed as pure small-ceil carcinoma but

proved to have a mixed tumor at either sur-

gery or autopsy. Of the 17 patients, eight

received chemotherapy, and four had a par-

tial response. Six of the 40 autopsies per-

formed on patients with small-cell lung can-

cer demonstrated intrathoracic tumor which

was histologically mixed. Extrathoracic

metastases in these patients were

heterogeneous and included pure small-cell,

pure non-small-ceil, and mixed histologic

type. We conclude that mixed small-cell and

non-small-cell lung cancers are relatively

frequent and carry important prognostic and

therapeutic implications. Clinical manage-

ment of patients with small-cell lung cancer

should therefore be flexible and tailored to

the potential for histologic diversity.

Mixed lung cancer in previously untreated

patients suggests a common endodermal origin

for small-cell and non-small-ceil pulmonary

tumors.

Scar Adenocarcinoma of the Lung: A Light and

Electron Microscopic Study.

Edwards, C., Carlile, A. Department of His-

topathology, East Birmingham Hospital, Bir-

mingham B9 5ST, U.K.J. Clin. Pathol. 39:

423-427, 1986.

Five well differentiated peripheral

adenocarcinomas of the lung were inves-

tigated, using light and electron micros-

copy. Each tumour contained a central nidus