Nesrin GÜRÇAY, Funda DEMİRAĞ, Müzeyyen Burcu Kaplan YILMAZ, Çiğdem Yıldırım MAYDA, Hilal AKGÜL, Pınar Akın KABALAK, Betül Bahar İŞGİR
Acta Haematologica Oncologica Turcica - 2026;59(2):120-125
Aim: Accurate subclassification of non-small cell lung carcinoma (NSCLC) in small biopsy specimens is essential for appropriate therapeutic decision-making and molecular testing. However, accurate subclassification remains challenging in a subset of tumors, particularly in those lacking both thyroid transcription factor-1 (TTF-1) and p40 expression. This study aimed to evaluate the diagnostic contribution of histochemical mucicarmine positivity in the adenocarcinoma-oriented subclassification of TTF-1 and p40-negative NSCLC cases diagnosed from small biopsy specimens. Methods: This retrospective study included 120 NSCLC cases that were negative for TTF-1 and p40, diagnosed from small biopsy specimens. All cases underwent histochemical mucicarmine staining. Clinicopathological variables, including patient age, sex, biopsy type, mucin staining pattern, initial diagnostic category, and method of final diagnostic confirmation, were evaluated. Statistical analyses were performed using the chi-square and Fisher's exact tests. Results: The mean age of the patients was 67.75+/-9.82 years, and 81.7% of the patients were male. Histochemical mucin positivity was observed in 116 of 120 cases (96.7%): focal in 45 cases (37.5%), diffuse in 41 cases (34.2%), and of unspecified extent in 30 cases (25.0%). Only four cases (3.3%) were mucin- negative and remained classified as NSCLC-not otherwise specified (NSCLC-NOS). A statistically significant association was observed between mucin positivity and adenocarcinoma-oriented subclassification (p<0.001). No significant association was identified between biopsy modality and mucin positivity (p=0.296). Conclusion: Histochemical mucicarmine positivity provides valuable diagnostic support for adenocarcinoma-oriented subclassification in TTF-1- and p40-negative NSCLC cases diagnosed on small biopsy specimens. Mucicarmine staining is a practical, inexpensive, tissue-preserving adjunctive technique that may help reduce the frequency of NSCLC-NOS diagnoses in diagnostically challenging cases.
