Pancreatic adenosquamous carcinoma mimicking autoimmune pancreatitis

A 78-year-old man presented with upper abdominal pain for two months. He had a decades-long history of well-controlled diabetes, managed with insulin degludec and acarbose. However, his glycemic control had worsened in the past month.

Laboratory tests showed elevated serum IgG4 (3,482 mg/L) and increased hemoglobin A1c (9.7%). CA19-9 and amylase were all within normal reference intervals.

Magnetic resonance imaging (MRI) (Figure 1A-1C) showed diffuse enlargement of the pancreas with decreased T1 and increased T2 signal, more prominent in the body and tail. Post-contrast images revealed mildly decreased and heterogeneous enhancement. At this stage, autoimmune pancreatitis (AIP) was highly suspected.

Figure 1 Findings from MRI (A-C) and EUS (D-F). (A) On fat-suppressed T2-weighted images, there is diffuse enlargement of the pancreatic body and tail with high signal intensity. (B) Diffusion-weighted imaging demonstrates markedly increased signal within the lesion. (C) On contrast-enhanced images during the delayed phase, the lesion shows conspicuous heterogeneous enhancement with internal linear septations. (D) Diffuse coarsening of the pancreatic parenchymal echotexture with pancreatic enlargement. (E) Scattered small, round anechoic areas within the pancreas; punctate and linear hyperechoic foci within the pancreatic parenchyma. (F) Puncture using a 22-gauge fine needle under EUS guidance. EUS, endoscopic ultrasound; MRI, magnetic resonance imaging.

In order to exclude malignancy, the patient underwent endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB). Diffuse enlargement of the pancreas with an irregular contour was noted (Figure 1D). The pancreatic parenchyma exhibited a heterogeneous echotexture, with scattered patchy and linear hyperechoic areas (Figure 1E) without “halo sign”. Multiple small round anechoic areas were observed within the pancreatic parenchyma (Figure 1E). The pancreatic duct showed no dilatation. A biopsy was performed using a 22-gauge FNB needle (BostonScientific Acquire^TM) to puncture the parenchyma of the pancreatic body and tail (Figure 1F).

Immunohistochemical analysis (Figure 2A-2D) revealed diffuse positivity for CK7, indicating glandular epithelial differentiation, while partial positivity for P40 and P63 indicated squamous differentiation. The coexistence of both glandular and squamous components supports the diagnosis of pancreatic adenosquamous carcinoma (1). Given the presence of distant metastases confirmed by further evaluation, the patient subsequently received oral gemcitabine chemotherapy and passed away four months after diagnosis. Diffuse changes of the pancreas, especially when accompanied by elevated IgG4 levels, can easily lead to missed diagnoses of cancer; therefore, biopsy is sometimes necessary. In this pancreatic cancer case, the pancreas shows diffuse involvement, but it lacks the typical EUS features of AIP, which are summarized in Table S1.

Figure 2 Pathological examination confirmed the diagnosis of pancreatic adenosquamous carcinoma. (A) H&E staining of the pancreatic biopsy demonstrates a mixture of malignant glandular and squamous components. (B) Immunohistochemical staining for P63 confirms squamous epithelial differentiation. (C) Immunohistochemical staining for P40 confirms squamous epithelial differentiation. (D) Immunohistochemical staining for CK7 highlights glandular epithelial differentiation. Scale bar: 100 µm (applicable to all panels). H&E, hematoxylin and eosin.

Acknowledgments

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Footnote

Provenance and Peer Review: This article was a standard submission to the journal. The article has undergone external peer review.

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Funding: The work was financially supported by Beijing Natural Science Foundation (No. L232120) and CAMS Innovation Fund for Medical Sciences (CIFMS) (No. 2023-I2M-2-002).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://hbsn.amegroups.com/article/view/10.21037/hbsn-2025-aw-833/coif). The authors have no conflicts of interest to declare.

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References

1. Zhang W, Zhang J, Liang X, et al. Research advances and treatment perspectives of pancreatic adenosquamous carcinoma. Cell Oncol (Dordr) 2023;46:1-15. [Crossref] [PubMed]