Metastatic Potentiality of Micropapillary and Conventional Histological Patterns: A Comparative Study of 82 Pulmonary Adenocarcinomas
Chavit Chantranuwat MD*
Affiliation : *Department of Pathology, Faculty of Medicine, Chulalongkorn University
Background : The recently described micropapillary pattern (MPP) is potentially a strong unfavorable prognostic marker
for adenocarinoma of the lung. None of the previous studies compared the association to nodal metastasis between
conventional histological patterns and MPP.
Method : Histological patterns (1=solid, 2=poorly formed acinar, 3=well formed acinar, 4=papillary, 5=bronchioloalveolar),
and MPP were semiquantitatively evaluated in 82 pulmonary adenocarcinomas and correlated with nodal status.
Results : Mean percentages of pattern 1 and 2 are higher in node positive (N+) group (33.9% vs 19.3%, p=0.046; and
20.8% vs 13.4%, p=0.19, respectively). Analysis of the combined amount of pattern 1 and 2 revealed increased statistical
significance (54.6% vs 32.5%, p=0.007). Mean percentages of pattern 3, 4 and 5 tended to be lower in N+ group (22.8%
vs 29.4%, p=0.24; 2.8% vs 6.2%, p=0.33; and 17.9% vs 31.2%, p=0.053, respectively). Analysis of the combined amount
of pattern 3,4 and 5 showed increased statistical significance (43.3% vs 66.8%, p=0.005). Mean percentage of MPP was
higher in N+ group (28.3% vs 11.3%, p=0.0007) after excluding the cases with more than 80% percent of pattern 1 and
2. The criterion of MPP > 20% or combined pattern 1 and 2 >50% of tumor is strongly associated with nodal metastasis
(p=0.0015). Pattern 1 has the highest rate of correspondence of having a similar pattern in metastases (18/26, 69.2%),
followed by MPP (10/19, 52.6%), and pattern 2 (12/23, 52.2%).
Conclusion : MPP has comparable metastatic impact to the solid and the poorly formed acinar patterns and it is prog-
nostically informative to document the presence or absence of the solid plus poorly formed glandular pattern > 50% and
MPP > 20% when histological subtype is evaluated.
Keywords : Lung, Adenocarcinoma, Micropapillary, Histological subtypes, Metastasis, Prognostic marker
