Performance differences between conventional smears and liquid-based preparations of thyroid fine-needle aspiration samples: analysis of 47,076 responses in the College of American Pathologists Interlaboratory Comparison Program in Non-Gynecologic Cytology

CONTEXT

Controversy exists about whether thyroid fine-needle aspirates (FNAs) should be processed with conventional smears or liquid-based preparations (LBPs).

OBJECTIVE

To compare the performance of conventional smears to LBPs for thyroid FNA slides circulated in the College of American Pathologists Interlaboratory Comparison Program in Non-Gynecologic Cytology.

DESIGN

Participant responses for thyroid FNA slides were compared with the reference diagnosis at the level of 3 general diagnostic categories: negative, suspicious (which included only follicular and Hürthle cell neoplasm), and malignant. For specific reference diagnoses of benign/goiter and papillary thyroid carcinoma, the participants' specific diagnoses were analyzed and poorly performing slides were rereviewed.

RESULTS

The 47, 076 thyroid FNA slide responses, between 2001 and 2009, included 44, 478 responses (94%) for conventional smears and 2598 responses (6%) for LBPs. For the general reference category negative, participant responses were discrepant in 14.9% of conventional smears compared with 5.9% for LBPs (P < .001). The specific reference diagnosis of benign/goiter was misdiagnosed as a follicular neoplasm in 7.8% of conventional smears, compared with 1.3% of LBP. For the general reference category of malignant, participant responses were discrepant in 7.3% of conventional smears compared with 14.7% of LBPs (P < .001). The specific reference diagnosis of papillary thyroid carcinoma was misdiagnosed as benign/goiter in 7.2% of LBPs, compared with 4.8% of conventional smears (p <.001).

CONCLUSIONS

LBPs performed worse than conventional smears for cases with a reference diagnosis of papillary thyroid carcinoma. However, LBPs performed better than conventional smears for cases with a benign reference diagnosis. Specific features in thyroid FNAs that may improve the diagnostic accuracy of LBPs and conventional smears are described.

Review of advanced imaging techniques

Pathology informatics encompasses digital imaging and related applications. Several specialized microscopy techniques have emerged which permit the acquisition of digital images (“optical biopsies”) at high resolution. Coupled with fiber-optic and micro-optic components, some of these imaging techniques (e.g., optical coherence tomography) are now integrated with a wide range of imaging devices such as endoscopes, laparoscopes, catheters, and needles that enable imaging inside the body. These advanced imaging modalities have exciting diagnostic potential and introduce new opportunities in pathology. Therefore, it is important that pathology informaticists understand these advanced imaging techniques and the impact they have on pathology. This paper reviews several recently developed microscopic techniques, including diffraction-limited methods (e.g., confocal microscopy, 2-photon microscopy, 4Pi microscopy, and spatially modulated illumination microscopy) and subdiffraction techniques (e.g., photoactivated localization microscopy, stochastic optical reconstruction microscopy, and stimulated emission depletion microscopy). This article serves as a primer for pathology informaticists, highlighting the fundamentals and applications of advanced optical imaging techniques.

Confocal Laser Endomicroscopy: A Primer for Pathologists

Context.—The advent of new endoscopic optical techniques is likely to change pathologists' role in diagnosis.

Objective.—To describe how confocal laser endomicroscopy (CLE) works, show its advantages and limitations compared to cytohistologic biopsy, and explore how it may affect the practice of pathology.

Data Sources.—Literature review.

Conclusions.—Confocal laser endomicroscopy is proving its ability to provide histology-like images of tissues in vivo to help avoid risks and costs of conventional biopsies. Confocal imaging restricts light to 1 plane, emulating a paraffin section, and topical or systemic optical contrast agents allow subcellular resolution. New contrast agents could theoretically permit molecular characterization. In vivo imaging has begun to demonstrate novel, dynamic types of diagnostic features. Decreased histologic biopsies can be anticipated for a few scenarios. Significant limitations of CLE include the inability to create a tissue archive for broad molecular classification, suboptimal contrast agents, small fields of view and shallow penetration, paucity of clinical validation studies, and problems with reimbursement. Confocal laser endomicroscopy exposes new opportunities for pathologists: CLE technologies can be exploited in pathology, and diagnostic criteria expanded based on endoscopists' discoveries. Potential synergy exists between CLE and cytology, allowing the low-magnification diagnostic architectural changes by CLE and cytomorphology to emulate the full diagnostic information in a histologic biopsy while providing an archive of material for molecular or immunohistochemical studies. Confocal laser endomicroscopy will decrease some types of biopsies, but offers an opportunity for pathologists to find new ways to provide value and improve patient care.

Advances in microscopy techniques

CONTEXT

Advances in microscopy enable visualization of a broad range of new morphologic features.

OBJECTIVE

To review and illustrate advances in microscopy with relevance to pathologists.

DATA SOURCES

Literature review and new observations.

RESULTS

Fluorescence microscopy enables multiantigen detection; allows novel optical-sectioning techniques, with some advantages compared to paraffin sectioning; and permits live-cell imaging. Live-cell imaging allows pathologists to move from a period when all diagnostic expertise was reliant on interpreting static images to a period when cellular dynamics can play a role in diagnosis. New techniques have bypassed by about 100-fold what had long been believed to be a limit to the resolution of light microscopy. Fluorescence resonance energy transfer (FRET) appears capable of visualizing diagnostically relevant molecular events in living or fixed cells that are immeasurable by other molecular techniques. We describe applications of 2-photon microscopy, FRET, structured illumination, and the subdiffraction techniques of near-field microscopy, photoactivated localization microscopy, stochastic optical reconstruction microscopy, and stimulated emission depletion microscopy.

CONCLUSION

New microscopy techniques present opportunities for pathologists to develop improved diagnostic tests.

Targeting BRAFV600E with PLX4720 displays potent antimigratory and anti-invasive activity in preclinical models of human thyroid cancer

PURPOSE

B-Raf(V600E) may play a role in the progression from papillary thyroid cancer to anaplastic thyroid cancer (ATC). We tested the effects of a highly selective B-Raf(V600E) inhibitor, PLX4720, on proliferation, migration, and invasion both in human thyroid cancer cell lines (8505c(B-RafV600E) and TPC-1(RET/PTC-1 and wild-type B-Raf)) and in primary human normal thyroid (NT) follicular cells engineered with or without B-Raf(V600E).

EXPERIMENTAL DESIGN

Large-scale genotyping analysis by mass spectrometry was performed in order to analyze >900 gene mutations. Cell proliferation and migration/invasion were performed upon PLX4720 treatment in 8505c, TPC-1, and NT cells. Orthotopic implantation of either 8505c or TPC-1 cells into the thyroid of severe combined immunodeficient mice was performed. Gene validations were performed by quantitative polymerase chain reaction and immunohistochemistry.

RESULTS

We found that PLX4720 reduced in vitro cell proliferation and migration and invasion of 8505c cells, causing early downregulation of genes involved in tumor progression. PLX4720-treated NT cells overexpressing B-Raf(V600E) (heterozygous wild-type B-Raf/B-Raf(V600E)) showed significantly lower cell proliferation, migration, and invasion. PLX4720 treatment did not block cell invasion in TPC-1 cells with wild-type B-Raf, which showed very low and delayed in vivo tumor growth. In vivo, PLX4720 treatment of 8505c orthotopic thyroid tumors inhibited tumor aggressiveness and significantly upregulated the thyroid differentiation markers thyroid transcription factor 1 and paired box gene 8.

CONCLUSIONS

Here, we have shown that PLX4720 preferentially inhibits migration and invasion of B-Raf(V600E) thyroid cancer cells and tumor aggressiveness. Normal thyroid cells were generated to be heterozygous for wild-type B-Raf/B-Raf(V600E), mimicking the condition found in most human thyroid cancers. PLX4720 was effective in reducing cell proliferation, migration, and invasion in this heterozygous model. PLX4720 therapy should be tested and considered for a phase I study for the treatment of patients with B-Raf(V600E) ATC.

Atypical follicular cells with equivocal features of papillary thyroid carcinoma is not a low-risk cytologic diagnosis

OBJECTIVE

To determine whether or not significant differences in the risk of malignancy exist between subgroups of atypical follicular cells in The Bethesda System for Reporting Thyroid Cytology (TBSRTC) in patients who underwent surgical resection.

STUDY DESIGN

Between 2004 and 2009, consecutive thyroid fine-needle aspirates at our institutions with a cytologic diagnosis of 'atypical follicular cells' were retrieved and subclassified using the diagnosis and diagnostic comment as: (1) atypical follicular cells with equivocal features of papillary carcinoma [cannot exclude papillary thyroid carcinoma (PTC)] and (2) atypical follicular cells, other patterns. The risks of malignancy for excised nodules were calculated and comparisons were made between these subgroups. Categorical analysis was performed using a 2-tailed Fisher's exact test, and p < 0.05 was considered statistically significant.

RESULTS

A total of 7,072 thyroid fine-needle aspiration cases were retrieved, with 1,542 (21.8%) having a histologic follow-up. There were 222 (3.1%) cases of 'atypical follicular cells', with 127 (57.2%) having a histologic correlation and 33 having confirmed malignancies. Atypical follicular cells, cannot exclude PTC, have a significantly higher risk of malignancy than atypical follicular cells, other patterns (45.8 vs. 13.9%, p < 0.01).

CONCLUSIONS

Atypical follicular cells with equivocal features of papillary carcinoma is not a low-risk cytologic diagnosis.

Hemosiderin laden macrophages and hemosiderin within follicular cells distinguish benign follicular lesions from follicular neoplasms

Background:

Published criteria to distinguish benign colloid nodules from follicular neoplasms emphasize only three interdependent features: size of follicles, amount of colloid, and cellularity. There is a need for the validation of other independent criteria.

Methods:

This study quantified the significance of cystic change, defined as presence of macrophages, and the presence of hemosiderin in either the macrophages or follicular cells. The cohort consisted of 165 patients with fine needle aspiration (FNA) and histologic follow-up of either goiter (101), follicular adenoma (47), or follicular carcinoma (17). Papillary thyroid carcinomas and Hürthle cell neoplasms were excluded from the cohort, because these categories are known to show cystic change and hemosiderin. FNAs were reviewed blindly with the most cellular slide scored for the presence of macrophages and/or hemosiderin.

Results:

Hemosiderin within macrophages were seen in 67% (68 of 101) of the goiters and only 6% (four of 64) of follicular neoplasms (P<.0001). All four follicular neoplasms with hemosiderin in macrophages were adenomas. Three of these four had equivocal features of a benign colloid nodule histologically. None of the 17 follicular carcinomas had hemosiderin in macrophages (P<.12). Macrophages without hemosiderin also strongly distinguished goiters from neoplasms (83% vs 17%) but appears less useful as a criterion since macrophages were present within 3 of 17 follicular carcinomas. Hemosiderin within follicular epithelial cells was present in 18% (18 of 101) of goiters, whereas none of the 64 follicular neoplasms had intraepithelial hemosiderin (P<.0003).

Conclusions:

If papillary thyroid carcinoma and Hürthle cell neoplasm are ruled out, our findings indicate that the presence of hemosiderin virtually excludes a clinically significant follicular neoplasm.

Cryosectioning tissues

INTRODUCTIONCryosections are rapidly and relatively easily prepared prior to fixation, and they provide a good system for visualizing fine details of the cell. Although cryosections are physically less stable than paraffin- or resin-embedded sections, they are generally superior for the preservation of antigenicity and therefore the detection of antigens by microscopy. The preparation of cryosections does not involve the dehydration steps typical of other sectioning methods, and, furthermore, sectioning, labeling, and observation of specimens can usually be carried out in one day. In general, the sample is frozen quickly in either isopentane or liquid nitrogen. (Small samples such as cells and small tissues may be mixed in a slurry of an inert support medium such as optimal cutting temperature [OCT] compound before freezing). Rapid freezing reduces ice crystal formation and minimizes morphological damage. Frozen sections may be used for a variety of procedures, including immunochemistry, enzymatic detection, and in situ hybridization. A protocol for cryosectioning is presented here.

Fixation and permeabilization of cells and tissues

INTRODUCTIONFluorescence microscopy is used to visualize specific cellular components in as native a state and organization as possible. This article describes some of the main issues that must be considered when cells and tissues are fixed and permeabilized. To preserve cellular structure, the specimen is fixed chemically to retain the cells or tissue in a state as near to life as possible by rapidly terminating all enzymatic and other metabolic activities to minimize post-fixation changes. Sample fixation is one of the most crucial steps in assuring the accuracy of detection protocols and is therefore decisive in determining the subsequent success or failure of a given experiment. Underfixation of the sample leads to poor morphological preservation and/or loss of signal, whereas overfixation may lead to fixation artifacts, loss of signal, and/or increased nonspecific background signals ("noise"). An ideal fixative should preserve a given antigen in a fashion that reflects the in vivo situation with respect to its distribution (no diffusion or rearrangement). Ideally, cell morphology should be preserved, the antigen of interest should remain accessible to the probe, and the fixation should cause minimal denaturation of the antigen. However, several of these goals are mutually incompatible, and therefore, a compromise must be attained.

Paraffin embedding tissue samples for sectioning

INTRODUCTIONThis protocol describes a method for embedding tissues in paraffin blocks for sectioning. Paraffin sections require extensive fixation and processing steps, but provide superior morphology compared with other sectioning methods.

Decalcifying tissues for paraffin embedding

INTRODUCTIONParaffin sections of bone usually require a decalcification step after fixation before sectioning. This protocol describes a method for decalcifying fixed tissue.

Hematoxylin and eosin staining of tissue and cell sections

INTRODUCTIONHematoxylin and eosin (H&E) stains have been used for at least a century and are still essential for recognizing various tissue types and the morphologic changes that form the basis of contemporary cancer diagnosis. The stain has been unchanged for many years because it works well with a variety of fixatives and displays a broad range of cytoplasmic, nuclear, and extracellular matrix features. Hematoxylin has a deep blue-purple color and stains nucleic acids by a complex, incompletely understood reaction. Eosin is pink and stains proteins nonspecifically. In a typical tissue, nuclei are stained blue, whereas the cytoplasm and extracellular matrix have varying degrees of pink staining. Well-fixed cells show considerable intranuclear detail. Nuclei show varying cell-type- and cancer-type-specific patterns of condensation of heterochromatin (hematoxylin staining) that are diagnostically very important. Nucleoli stain with eosin. If abundant polyribosomes are present, the cytoplasm will have a distinct blue cast. The Golgi zone can be tentatively identified by the absence of staining in a region next to the nucleus. Thus, the stain discloses abundant structural information, with specific functional implications. A limitation of hematoxylin staining is that it is incompatible with immunofluorescence. It is useful, however, to stain one serial paraffin section from a tissue in which immunofluorescence will be performed. Hematoxylin, generally without eosin, is useful as a counterstain for many immunohistochemical or hybridization procedures that use colorimetric substrates (such as alkaline phosphatase or peroxidase). This protocol describes H&E staining of tissue and cell sections.

Cutting sections of paraffin-embedded tissues

INTRODUCTIONThis protocol describes the sectioning of tissues embedded in paraffin blocks. Paraffin sections require extensive fixation and processing steps but provide superior morphology compared with other sectioning methods. Sectioning paraffin blocks requires experience and should be learned from an experienced researcher, if possible.

Preparation of slides and coverslips for microscopy

INTRODUCTIONIt is imperative that the slides and coverslips used in fluorescence microscopy procedures be extremely clean. Although coverslips look clean, especially when a new box is first opened, they may have a thin film of grease on them that will not allow tissue culture cells to adhere well and that may interfere with some processing steps in certain protocols. Therefore, coverslips should routinely be washed with acid or base solutions to rid them of this film. Commercial precleaned slides are also likely to be dirty and must be washed prior to use. This protocol describes various approaches for cleaning slides and coverslips and sterilizing them for cell culture, as well as methods for subbing slides. In the subbing procedure, slides are coated with gelatin, aminoalkylsilane, or poly-L-lysine solution to promote the adhesion of cells or tissues to the glass surface. Gelatin or aminoalkylsilane is usually used for tissue sections or small organisms, whereas poly-L-lysine is routinely used for cultured cells.

Media for mounting fixed cells on microscope slides

INTRODUCTIONAfter a specimen is labeled, coverslips containing cells or tissues are mounted onto microscope slides, or slides containing sections are overlaid with a coverslip. A number of recipes for commonly used mounting media are presented in this article, each with particular recommendations.

Use of IMP3 in identification of carcinoma in fine needle aspiration biopsies of pancreas

OBJECTIVE

To evaluate insulin-like growth factor-II mRNA binding protein 3 (IMP3), which is an oncofetal RNA-binding protein expressed in pancreatic carcinomas and detectable by immunohistochemistry, in diagnosis of pancreatic cancer.

STUDY DESIGN

We retrospectively identified 25 consecutive pancreatic endoscopic ultrasound-guided fine needle aspiration biopsies with available cell blocks, including 12 invasive pancreatic ductal carcinomas and 13 cases of chronic pancreatitis. Immunostains were performed on 4-microm tissue sections using standard techniques. Cytoplasmic staining of the lesional cells and nonneoplastic pancreatic tissue was evaluated, and the intensity of staining was recorded as absent, weak, moderate or strong.

RESULTS

Eleven (92%) adenocarcinomas demonstrated staining of tumor cells with IMP3. The staining reaction was weak in 2 of 11 (18%), moderate in 5 of 11 (45%) and strong in 4 of 11 (36%) of the cases. Nonneoplastic pancreatic tissues, present in 8 of 12 carcinomas and 13 cases of chronic pancreatitis, were negative for IMP3.

CONCLUSION

IMP3 is a promising new marker with high specificity and sensitivity for pancreatic adenocarcinoma.

Mounting live cells attached to coverslips for microscopy

INTRODUCTIONThis article describes the mounting of coverslips containing live cells onto microscope slides.

Expression of a novel oncofetal mRNA-binding protein IMP3 in endometrial carcinomas: diagnostic significance and clinicopathologic correlations

Insulin-like growth factor-II mRNA-binding protein 3 (IMP3) is a newly identified oncofetal mRNA-binding protein that is involved in embryogenesis and carcinogenesis of some malignant neoplasms. To investigate the diagnostic and clinicopathologic significance of this protein in endometrial carcinomas, we evaluated immunohistochemical expression of IMP3 in the two most common forms of endometrial malignancies, endometrioid adenocarcinoma and serous carcinoma. We selected 167 endometrial adenocarcinoma cases including 122 cases of endometrioid adenocarcinoma and 45 cases of serous carcinoma. Twenty samples of benign endometrium obtained from 20 patients with nonmalignant uterine lesions were used as controls. Positive immunohistochemical stain for IMP3 was identified in all serous carcinoma cases, among which, 39 (86%) and 3 (7%) cases showed IMP3 immunoreactivity in >50%, and 21-50, or 6-20% of tumor cells, respectively. Immunohistochemical reaction intensity for IMP3 was identified to be strong in 38 (84%) and intermediate in 7 (16%) cases of serous carcinoma. Fifty-four (44%) cases of endometrioid adenocarcinoma were negative for IMP3. Thirty (25%), 20 (16%), 10 (8%), and 8 (7%) cases of endometrioid adenocarcinoma demonstrated positive immunoreactivity for IMP3 in 1-5, 6-20, 21-50, and >50% of the tumor cells. Strong IMP3-staining intensity was noted in 34 (28%), intermediate in 26 (21%), and weak in 8 (7%) cases of endometrioid adenocarcinoma. All 20 control cases were negative for IMP3. To compare p53 with IMP3 expressions, we found that 35 (78%) of the serous carcinoma cases showed strong p53 immunohistochemical activity in >50% of the tumor cell nuclei. In contrast, 11 of 112 (10%) endometrioid adenocarcinoma cases demonstrated strong p53 positivity in >50% of the tumor cell nuclei. In conclusion, our findings demonstrate significant expression of IMP3 in serous carcinoma as compared to endometrioid adenocarcinoma (P<0.0001). Expression of IMP3 and p53 may be helpful biomarkers in the distinction of endometrial serous carcinoma from endometrioid adenocarcinoma. In addition, expression of IMP3 in endometrioid adenocarcinoma correlates with higher nuclear and architecture grades of the tumor (P=0.0000 and P=0.0002, respectively).

Cell blocks of breast FNAs frequently allow diagnosis of invasion or histological classification of proliferative changes

Two major limitations of breast fine needle aspiration (FNA) compared with core needle biopsies (CNB) are the inability to determine whether a cancer is invasive and to classify proliferative lesions. We studied 40 consecutive "rapid cell blocks" from breast FNAs with surgical pathology follow-up to test whether cell blocks can overcome these limitations. Of 25 carcinomas, invasion could be identified in the cell block sections in 11 (44%). One cystosarcoma phyllodes was suspected based on the cell block sections. Cell blocks from 12 of 14 benign breast FNAs showed sufficient cells to assign a histologic diagnosis of no hyperplasia (1 case, confirmed on follow-up) and usual hyperplasia (11 cases; confirmed in eight of 11 on follow-up). Specific histologic diagnoses included intraductal papilloma (2 cases), and in situ lobular neoplasia (2 cases). Cell blocks complement smears and monolayers and appear to overcome major limitations of breast FNA.