Accurate diagnosis of histological type is important for
therapy selection in
lung cancer. Immunohistochemical (IHC) and histochemical stains are often used to
complement morphology for definite diagnosis and are incorporated in the WHO classification. Our main aim was to compare different
mucin stains and assess their value in relation to common IHC analyses in
lung cancer diagnostics. Using tissue microarrays from 657 surgically treated primary
lung cancers, we evaluated the
mucin stains
periodic acid-Schiff with
diastase (PASD),
alcian blue-
periodic acid-Schiff (ABPAS) and
mucicarmine, and compared with the IHC markers p40, p63,
cytokeratin 5,
thyroid transcription factor 1 (TTF-1), napsin A and
cytokeratin 7. Ten or more cytoplasmic
mucin inclusions in a tissue microarray core were seen in 51%, 48% and 31% of the 416
adenocarcinomas and 3%, 4% and 0.5% of the 194
squamous cell carcinomas with PASD, ABPAS and
mucicarmine, respectively. Diagnostic pitfalls, such as entrapped benign epithelium, apoptotic/necrotic cells and
glycogen, partly differed for the
mucin stains. TTF-1 and napsin A IHC stainings had similar specificity but better sensitivity for
adenocarcinoma than the
mucin stains, but addition of PASD or ABPAS identified more
tumors as
adenocarcinomas (n = 8 and n = 10, respectively) than napsin A (n = 1) in cases with solid growth that were negative for TTF-1 and p40. We conclude that PASD and ABPAS have similar diagnostic performance and that these markers are of value in poorly differentiated cases. However, morphology and TTF-1 and p40 IHC staining is sufficient for correct diagnosis in most non-small cell
lung cancers.