Molecular genetic profiling of a rare case of primary pulmonary adenoid cystic carcinoma: Insights from whole exome sequencing and literature review

Abstract

Background: Primary pulmonary adenoid cystic carcinoma (PPACC) is a rare neoplasm characterized by slow growth and low malignancy.

Aim: The study seeks to enhance understanding of PPACC through comprehensive analysis of a reported case, incorporating pathological diagnosis, immunohistochemistry, special staining, and molecular alterations identified via whole exome sequencing.

Methods: A retrospective analysis was conducted on a PPACC case treated at the institution, encompassing pathological examination, immunohistochemical profiling, special staining techniques, and molecular alterations revealed by whole exome sequencing.

Results: A 56-year-old male presented with a left lower lobe mass identified on chest CT during a routine health check. Clinical evaluation revealed dyspnea, and imaging showed a 25 × 18 mm nodule in the left lower lobe. Video-assisted thoracoscopic surgery was performed for left lower lobectomy, with intraoperative frozen pathology indicating a salivary gland-type tumor (2.5 × 2 × 1.7 cm). ENT examination and cervical MRI ruled out a primary salivary gland tumor. Routine paraffin-embedded pathology confirmed pulmonary adenoid cystic carcinoma without pleural invasion. Whole exome sequencing revealed mutations in MYB family genes and the ALK gene.

Conclusion: This study highlights the pathological and molecular characteristics of PPACC, including a cribriform pattern and specific genetic mutations. These findings underscore the necessity of enhancing clinical vigilance to avoid misdiagnosis and missed diagnosis of this disease.

Keywords: Diagnosis; Lung tumor; Pulmonary adenoid cystic carcinoma; Treatment.

Fig. 1

Microscopic images of primary pulmonary adenoid cystic carcinoma sections stained with hematoxylin and eosin. (A) Frozen section at 40x magnification. (B, C) Paraffin-embedded sections at 100x magnification, showing a cribriform arrangement of tumor cells. Red arrows indicate ductal cells, yellow arrows indicate myoepithelial cells, blue arrows indicate mucin within cribriform spaces, and black arrows indicate mitotic figures. Scale bar represents 100 μm.

Fig. 2

Microscopic images of immunohistochemical staining for various markers in primary pulmonary adenoid cystic carcinoma sections. Ductal epithelial markers: (A) CD117, (B) EMA, (C) CKpan; Myoepithelial markers: (D) DOG-1, (E) P63, (F) SMA; Proliferation index: (G) Ki-67. Positive staining appears brown. Red arrows indicate ductal cells, and yellow arrows indicate myoepithelial cells. All images are at 100x magnification, with a scale bar representing 100 μm.

Fig. 3

Microscopic images of special staining in primary pulmonary adenoid cystic carcinoma sections. (A) AB-PAS staining, with blue arrows indicating the blue-stained mucinous material within the lumen. (B) Staining of pleural elastic fibers, used to assess tumor invasion. Red arrows indicate tumor cells, and black arrows indicate intact and continuous green-stained elastic layers of the pleura. All images are at 100x magnification, with a scale bar representing 100 μm.