Cytomorphologic Correlates of
PD
‐
L1
Expression in Advanced Gallbladder Carcinoma: A Prospective Cross‐Sectional Study Using Fine Needle Aspiration
Pragya Verma, Parikshaa Gupta, Pankaj Gupta, Nalini Gupta, Radhika Srinivasan, Ritambhra Nada, Anupam Lal, Usha Dutta ABSTRACT
Background
Programmed death‐ligand 1 (PD‐L1) expression has been evaluated in gallbladder carcinoma (GBC), predominantly in histopathologic specimens, while the cytomorphologic correlates in advanced GBC remain poorly characterized. We evaluated PD‐L1 expression and its cytomorphologic associations in a prospective cohort of advanced GBC diagnosed by fine‐needle aspiration cytology (FNAC).
Methods
This prospective study included 70 treatment‐naïve patients with advanced GBC diagnosed by ultrasound‐guided FNAC. PD‐L1 immunocytochemistry was performed on FNAC‐derived cell blocks using the SP263 clone, and the tumour proportion score (TPS) was calculated. Associations between PD‐L1 expression and clinicoradiologic and cytomorphologic parameters were evaluated.
Results
PD‐L1 expression (TPS ≥ 1%) was identified in 14/70 (20%) tumours; 10 had TPS 1%–49% and four had TPS ≥ 50%. PD‐L1 expression differed significantly by cytologic subtype ( p = 0.046) and was more frequent in squamous cell carcinoma (4/6; 66.7%) than in conventional adenocarcinoma (9/55; 16.4%) (OR: 10.22; 95% CI: 1.62–64.47). A strong association was observed with nuclear pleomorphism ( p = 0.0001): 8/11 (72.7%) tumours with marked pleomorphism were PD‐L1‐positive compared with 6/56 (10.7%) with moderate pleomorphism (OR: 22.22; 95% CI: 4.60–107.25; Fisher's exact p = 0.0001). PD‐L1 expression was not significantly associated with cytologic grade or clinicoradiologic parameters.
Conclusions
PD‐L1 expression was identified in 20% of advanced GBCs diagnosed by FNAC. Marked nuclear pleomorphism and squamous differentiation were strongly associated with PD‐L1 positivity. These findings, although they require further large‐scale validation, expand the cytomorphologic characterization of PD‐L1‐expressing advanced GBC where surgical tissue is unavailable.