Malignant Epithelioid Pleural Mesothelioma Versus Peripheral Pulmonary Adenocarcinoma: A Histochemical, Ultrastructural, and lmmunohistologic Study of 103 Cases MAIRK R. WICK. MD, TIMOTHY LOY, MD, STACEY E. MILLS, MD, JACQUES F. LEGIER, MD, AND J. CARLOS MANIVEL, MD The distinction lioma (MEPM) pleural

between malignant and peripheral

invasion

(PAL)

epithelioid

continues

histochemical,

these neoplasms, MEPMs

chal-

data on

51 ultrastructurally

nohistologic

and colloidal

reagents.

membrane

categorized

to cytokeratin,

(EMA),

these three markers mesothelioma.

enocarcinomas.

studies revealed

long, branching

cases, with, length-to-diameter contrast, LDR

P’AL manifested

of 8:l

iron-positivity

to PAL,

well

neoplasms

expressed

in all cases, CEA

84%, and BGI

only such

results

in addition,

EMA,

All

correlated

MEPMs

was apparent

were re-

of the lung, Leu M 1 was in 96%, B72.3 labeled

were present in 67%; all PALS expressed

two of these determinants,

and

the majority of

and a minority

active for vimentin. In adenocarcinomas observed

However,

demonstrated

classification.

PALS were reactive for cytokeratin;

with

and hyaluronidase-sensitive

Immunohistologic

microscopic

tumors in ‘each group

microvilli

and mucicarmine

was restricted to MEPM.

reactivity.

with electron

cells in all

of 1O:l or more. In

with PAS-D

at least

but none was seen in any mesothelio-

ma. The other markers included

in this study also were observed

in some PA.L cases, hut not in MEPM.

antibodies

to

to exclude

a diagnosis

we studied

of pleural

oncoplacentofetal,

can be used to reinforce

since their distribution

HUM PATHOL 21:759-766.

is confined

to ad-

0 1990 by W.B. Saun-

The distinction between malignant epithelioid pleural mesothelioma (MEPM) and peripheral adenocarcinoma of the lung with pleural involvement (PAL) is a diagnostic challenge in selected cases. It has become a more common problem facing surgical pathologists in recent years because the incidence of MEPM appears to be increasing, at least in the United States.’ Moreover, lung cancer continues to represent a common malignancy as well.’ A variety of pathologic techniques have been advanced to separate cases of MEPM and PAL, including histochemical analysis,“-x electron microsassays.‘“-4” c(jpy, 4.9-17 and immunohistochemical With respect to the last of these procedures, correlations with ultrastructural data and histochemical results have been provided in only a few reports on the immunophenotypic attributes of the t.wo neoplasms since antiin question. 4.5.14,p6~J6This is unfortunate, body-enzyme methods are now widely available and could, if comparable in efficacy to other adjunctive techniques, improve the overall level of diagnostic certainty in this potentially difficult area of histopathology. Therefore, we were motivated to undertake the immunophenotypic study of a large number of MEPM and PAL cases which had been studied by electron microscopy and histochemistry. They provided the substrate for a meaningful assessment of immunohistologic procedures as applied to pleuropulmonary tumors.

Ultrastructural

in MEPM

short, nonbranching

63% and 41% of these respective histochemical

microvilli

in efficacy in the

Using

ders Company.

epi-

sections with the

technique.

ratios (LDR)

or less. Reactivity

stains was strictly confined colloidal

to paraffin

complex

and PAL.

antigen

amylase, SlOO protein, and Clara

cell antigen were used, as applied avidin-biotin-peroxidase

appears

antigens

such a determination,

(CEA), Leu Ml, the B72.3 antigen, blood group isoantigens (BGI), placental alkaline phosphatase,

electron microscopy

of MEPM

The other glycoproteinaceous,

and cytoplasmic

(PAS-

vimentin,

carcinoembryonic

parallels

separation

Leu Ml, CEA, and the B72.3 antigen, reactivity for at least two of

iron stains, and a panel of immu-

Antibodies

antigen

immunohistology diagnostic

features of

and 52 PALS with the periodic acid-Schiff-diastase

D), mucicarmine, thelial

comparative

and immunohistochemical

we analyzed

mesothe-

of the lung with

to represent a diagnostic

lenge in selected cases. In order to provide histologic,

pleural

adenocarcinoma

These findings suggest that

From the DiGsion of Surgical Pathology, Department of Pathology. University of Minnesota School of Medicine, Minneapolir. MN; the Division of Surgical Pathology, Department of Pathology. Lrniversity of Virginia Health Sciences Center, Charlottesville, VA; and the Division of Surgical Pathology, Department of. Pathology, Riverside Hospital. Newport News. VA. Accepted for publication November 11. 1989. Presented at the 77th Annual Meeting of the United States and Canadian Academy of Pathology. Washington. DC, March IYXX. Dr Wick is currently affiliated with Washington LTniversity School of Medicine, St Louis, MO. Dr Lo) is currently affiliated with the rniversitv of Missouri School of Medicine, Columbia. MO. mesothelioma. pseudomesotheKP~ wor~~c lung neoplasms, liomatous, adenocarcinoma. electron microscopv. immunoenzyme tc-chniques. Address correspondence and reprint requests to Mark K. Wick, MD, at the Division of Surgical Pathology, Barnes Hospital. Washington University Medical Center, 1 Barnes Hospital Plaza, St Louis, MO 63 1 IO. 0 lY9Clby W.B. Saunders