Fine-needle aspiration cytology of basaloid squamous cell carcinoma and small cell carcinoma-A comparison study

Neuroendocrine differentiation distinguishes basaloid variant of lung squamous cell carcinoma

Background

Neuroendocrine (NE) differentiation is widely studied in non-small cell lung carcinomas (NSCLC) however, its significance remains unclear in basaloid squamous cell carcinomas (B-SqCC). This study aims to assess the extent of NE differentiation in B-SqCC and characterize the underlying molecular process.

Methods

This study evaluated resected B-SqCC, small cell lung cancer (SCLC) and poorly differentiated SqCC (PD-SqCC) from 2005 to 2020 at the Ottawa Hospital. Samples were subject to pathological review, immunohistochemistry (IHC) and survival analysis. Gene expression analysis was performed on B-SqCC samples exhibiting NE+ and NE- regions (paired samples) to identify differentially expressed genes (DEGs). These DEGs were subsequently validated in unpaired B-SqCC and TCGA samples.

Results

B-SqCC cases were more likely to exhibit nuclear molding, resetting and peripheral palisading than PD-SqCC. B-SqCC were also more likely to demonstrate NE differentiation compared to PD-SqCC (p = 0.006). Pure basaloid squamous cell carcinoma (PB-SqCC) experienced poorer disease-free survival (HR = 3.12, p = 0.043) adjusted for stage.

Molecular characterization of paired B-SqCC samples demonstrated DEGs implicated in NOTCH signaling, SCLC and pulmonary neuroendocrine differentiation. Hierarchical clustering using discovered DEGs in unpaired B-SqCC samples distinguished tumors based on NE status (p = 0.048). Likewise, clustering The Cancer Genome Atlas (TCGA) samples with DEGs distinguished B-SqCC from SqCC samples (p = 0.0094).

Conclusion

This study provides IHC and molecular evidence of significant NE-differentiation in B-SqCC and demonstrates their aggressive clinical behavior. These findings suggest that B-SqCC are biologically distinct from SqCC and share characteristics with SCLC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13000-022-01223-6.

Architectural aspects of cell-blocks as small biopsies

Cell-block preparations have become an essential part of integrated cytology diagnosis. They are essentially microbiopsies that are formalin fixed and embedded in paraffin. This has become more prevalent with greater sample procurement due to the advent of newer biopsy techniques and needles. Cell-blocks allow retrieval of small tissue fragments from cytology specimens that sometimes cannot be processed by alternate cytologic techniques. They represent concentrated, cell-enriched preparations that provide cytologists with the opportunity to evaluate cellular architecture, as well as to perform ancillary testing. A cell-block compatible sample may thus obviate the need for a more invasive procedure such as a tissue biopsy. Microscopic examination of cell-blocks is quick, avoids obscuring material, permits cells to be evaluated in one focal plane, and allows the histologic architecture such as glandular differentiation, papillary formations, and sometimes invasion to be easily identified. This new era of “cytohistology” accordingly requires practicing cytologists to become more familiar with histopathology. This review article discusses the benefit of various architectural patterns identifiable in cell-blocks employed as an adjunct to Pap tests, exfoliative fluid specimens, and fine-needle aspirations.

The cytology of salivary gland neoplasms with globules of extracellular matrix: Case-based review of adenoid cystic carcinoma and its potential mimics

Fine needle aspiration (FNA) cytology is an important tool for diagnosing salivary gland neoplasms and for guiding clinical management. The classic adenoid cystic carcinoma (AdCC) is a basaloid neoplasm with abundant extracellular matrix. The presence globules of extracellular matrix are quite characteristic of AdCC but not diagnostic. We selected from our files six FNA cases that contained at least some globules of amorphous matrix that are similar to the ones seen in AdCC. The aim of this case-based review is to discuss the pitfalls and some of the common differential diagnoses of AdCC in FNA cytology. By the end of this review, we hope to have shared with the readers the lessons we learned from these cases and to highlight the key criteria needed to make a correct diagnosis of AdCC based on cytomorphology. The importance of considering other entities, in addition to AdCC, whenever a salivary gland FNA presents with globules is emphasized.

Abrupt Dyskeratotic and Squamoid Cells in Poorly Differentiated Carcinoma: Case Study of Two Thoracic NUT Midline Carcinomas with Cytohistologic Correlation

Cytologic diagnosis of nuclear protein in testis (NUT) midline carcinoma (NMC) is important due to its aggressive behavior and miserable prognosis. Early diagnosis of NMC can facilitate proper management, and here we report two rare cases of thoracic NMC with cytohistologic correlation. In aspiration cytology, the tumor presented with mixed cohesive clusters and dispersed single cells, diffuse background necrosis and many neutrophils. Most of the tumor cells had scanty cytoplasm and medium-sized irregular nuclei, which had fine to granular nuclear chromatin. Interestingly, a few dyskeratotic cells or squamoid cell clusters were present in each case. Biopsy specimen histology revealed more frequent squamous differentiation, and additional immunohistochemistry tests showed nuclear expression of NUT. Because this tumor has a notorious progression and has been previously underestimated in terms of its prevalence, awareness of characteristic findings and proper ancillary tests should be considered in all suspicious cases.

Cytomorphology of Basaloid Squamous Cell Carcinoma: A Diagnostic Dilemma

Basaloid Squamous Cell Carcinoma (BSCC) is an unusual and high grade variant of Squamous Cell Carcinoma (SCC) with a predilection for the upper aerodigestive tract. The cytomorphologic diagnosis of this tumour is challenging as it shares common cytomorphologic features with its differential diagnoses. However, a careful examination of the cytology can help in delivering a diagnosis of BSCC. In this case report we present the imprint cytology findings of histologically proven BSCC in a 60-year-old male who presented with an ulcerated lesion at the umbilical region.

The role of cytology in the era of HPV-related head and neck carcinoma

Enlarged neck lymph nodes are very often subject to fine needle aspiration biopsy to detect metastatic disease in patients with suspected or proven squamous cell carcinoma in head and neck region. Cytology specimens of metastatic carcinoma in such patients are routinely evaluated for human papilloma virus (HPV) to identify patients with HPV-related head and neck squamous cell carcinoma. Different types of cytology specimens including smears, cytospins, cell blocks and aspirated material in the rinse can all be used for different types of HPV testing such as immunohistochemistry for p16, HPV-in situ hybridization, and HPV-Polymerase chain reaction. There is currently no consensus regarding the testing of high-risk HPV in cytology specimens. The establishment of standardized HPV testing of cytology specimens is of utmost importance and is eagerly awaited.