Electron Microscopy Renders the Diagnostic Capabilities of Cytopathology More Precise: An Approach to Everyday Practice

Cytology is a powerful diagnostic tool but to make definitive diagnoses, the use of ancillary techniques is imperative. By combining immunohistochemistry (IHC) and electron microscopy (EM), cytologic diagnoses can be as precise as those of surgical pathology. In the authors' daily practice of cytopathology they use all ancillary techniques available to them: histochemistry, IHC, EM, flow cytometry, and molecular pathology. IHC is frequently used as an ancillary technique in their daily practice but EM is many times their technique of choice. By the use of EM the authors can make specific final diagnoses, make the diagnosis more definitive, narrow the differential diagnosis, or determine the origin of a neoplasm with unknown primary site. Specimens obtained by fine-needle aspiration as well as all body fluids are suitable for EM. The limiting factor is to obtain the appropriate material with the diagnostic cells for ultrastructural examination. The common diagnostic dilemmas in the everyday practice of cytology are the following: mesothelioma vs. adenocarcinoma, neuroendocrine differentiation or not, the distinction of melanoma from adenocarcinoma and sarcoma, hepatocellular carcinoma vs. adenocarcinoma, and the origin of adenocarcinomas of unknown primary. The authors discuss how they approach these diagnostic problems in their everyday practice and how they incorporate EM in solving them.     

The use of electron microscopy to refine diagnoses in the daily practice of cytopathology

Conceived as a screening tool, cytology is a field that since the 1980s has become more diagnostic in its scope. The advent of the fine-needle aspiration biopsy (FNAB) is responsible for cytology's new place in pathology. In the everyday practice of cytopathology, about 85-90% of the nongynecologic cases can be diagnosed with the use of routine stains (i.e., Papanicolaou and Diff Quik). The other 10-15% of the cases require the use of ancillary diagnostic techniques for a precise diagnosis. Immunohistochemistry helps solve approximately 50% of these cases, and the other half of these challenging cases are best approached and diagnosed by using electron microscopy (EM). In their practice, the authors obtain cytologic samples for EM routinely in difficult cases. Unfortunately, a percentage of these cases collected for ultrastructural evaluation do not have enough cells after processing, and others only have a few diagnostic cells available. In the cases in which at least a handful of cells are available, EM is almost invariably helpful in one way or another, either making a definitive diagnosis or refining the diagnosis. A sampling of FNAB cases from the authors' everyday practice is prevented to illustrate the use of EM in the practice of cytopathology. The cases have been selected from among the most common diagnostic challenges to highlight the important role that ultrastructural evaluation plays in a busy cytology practice. In our practice ultrastructural evaluation is a piece of the puzzle, which, along with the clinical history, clinical impression, light microscopic/cytologic features, and other ancillary techniques (IHC, flow cytometry, and molecular pathology), help compile an accurate diagnosis. Many times EM is the most important component of the diagnostic algorithm.     

An algorithmic approach to diagnostic cytopathology specimens

The key principles of optimal cytological evaluation include firstly, to make a morphological assessment and secondly, to collect adequate material for ancillary tests including immunohistochemistry and molecular analysis, if appropriate. “Rapid On Site Evaluation (ROSE)” is recommended by the RCPath Tissue pathways for Diagnostic Cytopathology given the benefits it offers which include the ability to control and manage the specimen to ensure adequate and high quality and triaging for ancillary tests. In this review, we will present our diagnostic algorithms for some specimens typically encountered by cytopathologists in day to day practice.     

Multidisciplinary approach to deep-seated lesions requiring radiologically-guided fine-needle aspiration

Fine-needle aspiration (FNA) is a diagnostic modality that continues to improve in accuracy as training and experience accumulate. With increasing operator expertise and improved localization techniques, greater numbers of patients are able to benefit from FNAs performed on sites that are otherwise difficult or dangerous to reach by conventional surgery. We present a retrospective review of a 2-yr experience with radiologically-guided deep-seated FNA. In 115 cases involving transthoracic and transabdominal sites, we achieved the following overall figures: 91.9% sensitivity, 100% specificity, 93.9% diagnostic accuracy, 100% positive predictive value, and 80.6% negative predictive value. Our results are compared to those in other series. When properly applied, FNA of deep-seated lesions through image guidance is equivalent to tissue diagnosis obtained by laparotomy or surgical procedures. The benefits of FNA with or without core biopsy vs. scalpel biopsy are readily apparent when one considers the morbidity, cost, turnaround time, and trauma to the patient. Diagn. Cytopathol. 1998;18:338–342. © 1998 Wiley-Liss, Inc.     

Fine-needle aspiration of basaloid squamous carcinoma: A case report with review of differential diagnostic considerations

Basaloid squamous carcinoma is a distinct variant of squamous carcinoma with a particularly poor prognosis. To our knowledge, there are only two papers in the cytopathology literature which describe this entity. We report the fine-needle aspiration findings of an additional case of metastatic basaloid squamous carcinoma in a cervical lymph node and compare its cytomorphologic features to those observed on touch imprints of the subsequent surgical specimen. Smears of the aspirate showed a mixed lymphoid background with interspersed cohesive clusters of small cells roughly 3 times the size of small mature lymphocytes. Some cells were angulated and others exhibited irregular nuclear contours. The cells were generally hyperchromatic with evenly staining dense chromatin or irregularly distributed coarse chromatin. Focally there was evidence of nuclear molding. On Diff-Quik staining, irregular globules of magenta-stained extracellular dense material were noted within or adherent to the periphery of some clusters or as somewhat linear formations with small epithelial cells clinging to the edges. Abundant mitotic figures and clumps of necrotic tumor were more apparent on touch preps of the subsequent surgical specimen. The differential diagnosis by fine-needle aspiration includes adenoid cystic carcinoma, basal-cell adenocarcinoma, adenosquamous carcinoma, and small-cell carcinoma. If a fine-needle aspirate of a cervical lymph node shows the features described above and the primary tumor is unknown, suggesting the possibility of metastatic basaloid squamous carcinoma may aid clinicians in the search for a primary site, as basaloid squamous carcinoma occurs most frequently at the base of the tongue, hypopharynx, and supraglottic larynx. Diagn. Cytopathol. 1998;19:210–215. Published 1998 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Contribution of transmission electron microscopy to fine-needle aspiration biopsy diagnosis: Comparison of cytology and combined cytology and transmission electron microscopy with final histological diagnosis

This report evaluates 74 fine-needle aspiration biopsies processed for transmission electron microscopy with subsequent surgical procedure. The specificity of diagnosis obtained by cytology alone was compared to that obtained by cytology and electron microscopy, using histologic diagnosis as the gold standard. When cytology gave a diagnosis of malignancy but could not give tumor category or type, electron microscopy could correctly give both. When cytology could give tumor category but not type, electron microscopy correctly identified type in the majority of cases. When cytology gave tumor category and type, electron microscopy confirmed the diagnosis. Transmission electron microscopy is very helpful when the cytopathologist can diagnose malignancy but cannot give tumor category and/or type. When the cytopathologist is specific in his/her diagnosis, TEM is not as helpful. Diagn Cytopathol 1996;15: 282–287. © 1996 Wiley-Liss, Inc.     

Electron Microscopy in the Diagnosis of Percutaneous Fine Needle Aspiration Specimens

Five years experience in the application of electron microscopy to fine needle aspiration biopsy specimens is reviewed. In an initial evaluation, 200 consecutive unselected specimens were examined; 89 proved diagnostic and, in a third of these, electron microscopy gave additional information that was often essential to diagnosis. Negative specimens resulted almost entirely from failure to obtain an adequate amount of material. Results were improved by the adoption of a preparation technique involving concentration of the cells in bovine serum albumin and by the inspection of a rapidly stained smear at the time of the aspiration procedure, with a further needle pass for electron microscopy being performed if necessary. Despite the small size of specimens, adequate examination was usually possible and electron microscopy has proved of value in the diagnosis of tumor samples acquired by fine needle aspiration in the same way as has been established with the larger sized specimens obtained by conventional biopsy and surgical resection.     

Electron Microscopy in the Diagnosis of Percutaneous Fine Needle Aspiration Specimens

Five years experience in the application of electron microscopy to fine needle aspiration biopsy specimens is reviewed. In an initial evaluation, 200 consecutive unselected specimens were examined; 89 proved diagnostic and, in a third of these, electron microscopy gave additional information that was often essential to diagnosis. Negative specimens resulted almost entirely from failure to obtain an adequate amount of material. Results were improved by the adoption of a preparation technique involving concentration of the cells in bovine serum albumin and by the inspection of a rapidly stained smear at the time of the aspiration procedure, with a further needle pass for electron microscopy being performed if necessary. Despite the small size of specimens, adequate examination was usually possible and electron microscopy has proved of value in the diagnosis of tumor samples acquired by fine needle aspiration in the same way as has been established with the larger sized specimens obtained by conventional biopsy and surgical resection.     

Fine-needle aspiration cytology of chondromyxoid fibroma: a case report

The cytologic presentation of a case of chondromyxoid fibroma studied by fine-needle aspiration in a 17-yr-old black male is described. The cytologic features of chondromyxoid fibroma are presented, and the differential diagnosis of intraosseous cartilaginous neoplasms is reviewed, emphasizing the cytomorphologic differentiation of chondromyxoid fibroma from chondrosarcoma, enchondroma, and chondroblastoma.     

Fine-needle aspiration cytology of pleuropulmonary blastoma: Case report and review of the literature

This report describes the fine-needle aspiration (FNA) cytology of a case of pleuropulmonary blastoma in a 3-yr-9-mo-old male. Pleuropulmonary blastoma is considered by most authors to be distinct from pulmonary blastoma and is a rare malignant tumor of the intrathoracic cavity. FNA smears were cellular with numerous small ovoid to spindled cells with oval to elliptical nuclei exhibiting finely granular chromatin and inconspicuous nucleoli. The cytoplasm was scant and cosinophilic with indistinct borders. Focal chondroid material and blastema-like cells were noted. The differential diagnosis suggested by the cytologic findings included rhabdomysosarcoma, teratoma, neuroblastoma, malignant mesenchymoma, pleuropulmonary blastoma, and metastatic tumor. To our knowledge, this is the first report of the cytology of this tumor. Diagn. Cytopathol. 16:336–340, 1997. © 1997 Wiley-Liss, Inc.     

Fine-needle aspiration cytology of soft-tissue calcinosis presenting as an enlarging mass in the chest wall

Calcinosis cutis is an uncommon condition, and calcific deposits in patients with end-stage renal disease are now somewhat rare, due to improvement in management. Since calcific deposits may clinically resemble a tumor, it is feasible to investigate them by fine-needle aspiration cytology (FNAC). A 52-yr-old male with a history of end-stage renal failure presented with a 2-cm mass in the left chest wall. Within 6 mo the mass enlarged to nearly four times its original size. In view of clinical suspicion of malignancy, FNAC was performed. Cytopreparations showed abundant calcium, indicative of soft-tissue calcinosis. The case is interesting, since the known history of end-stage renal failure enabled the FNAC diagnosis of soft-tissue calcinosis. Diagn. Cytopathol. 1998;19:465–467. © 1998 Wiley-Liss, Inc.     

Fine-needle aspiration cytology of soft tissue lesions: diagnostic challenges

Clinical and radiographic data provide important information in the evaluation of soft tissue lesions/neoplasms. Morphologic tissue and cytologic examination is considered to be a necessary part of the diagnostic work-up. The standard procedure for obtaining tumor tissue for morphologic evaluation has been incisional (open) or core needle biopsy. An increasing use of minimally invasive diagnostic procedures has resulted in better acceptance of fine-needle aspiration cytology (FNAC) in the diagnosis of soft tissue lesions. This article discusses challenges in FNAC of soft tissue lesions based on the experience at a multidisciplinary referral sarcoma center. Obtaining sufficient specimens from deeply seated small and necrotic/cystic lesions is technically a potential pitfall and misdiagnosis of cells from reactive zones surrounding the tumor as well as the correct evaluation of spindle cell lesions, rare soft tissue neoplasms, and "new entities" lacking reproducible cytological criteria are other important challenges in FNAC of soft tissues. The successful cytological evaluation of soft tissue lesions requires the application of strict, reproducible morphological criteria in the context of the clinical findings as well as ancillary techniques. The minimal criteria for diagnostic intervention in various clinical settings and the relative advantages and disadvantages of FNAC must be understood. FNAC of soft tissue lesions is facilitated when limited to specialized orthopedic-oncologic centers with a well-integrated multidisciplinary team and experience in the evaluation and therapy of soft tissue lesions.     

Fine-needle aspiration cytology of basal cell adenoma of the parotid gland: characteristic cytological features and diagnostic pitfalls

We retrospectively studied the cytological features of aspiration cytology in 12 cases of basal cell adenoma (BCA) and 5 cases mistakenly diagnosed as BCA. On macroscopic findings, the 12 cases of BCA included 7 cases of solid type and 5 cases of cystic type. The characteristic cytological features of solid type BCA were three-dimensional clusters in 71%, sharp-angle small clusters in 86%, basement membrane- like material in 71%, and cell crush in 86%. In contrast, 3 of the 5 cystic type BCA cases showed inadequate cellular components or no basaloid tumor cells, and the cytological diagnosis of BCA could not be determined. In the 5 cases misdiagnosed as BCA, there were 2 cases of pleomorphic adenoma, 2 cases of benign lymphoepithelial cyst, and 1 case of basal cell adenocarcinoma. Accurate differential cytological diagnosis of BCA is relatively easy to determine the solid type BCA, but is more difficult for cystic type BCA.     

Salivary neoplasia cytopathology: a logical diagnostic approach to cytological interpretation using histopathology knowledge

Fine needle aspiration cytology (FNAc) plays a vital investigative tool in the diagnostic and management pathway of the benign and malignant salivary pathologies. The current practice guidelines dictate acquirement of the nature of the salivary gland disease prior to embarking on definitive surgery. FNAc is a rapid, relatively easy, non-invasive diagnostic tool with minimal complications that achieves this goal. The diagnostic adequacy and the accuracy of FNAc sampling depends on a variety of factors including the operator aptness, lesional characteristics and patient factors. Hence the reported sensitivity of salivary cytology is variable and broad. However, the reported specificity is >90%. The diagnostic accuracy of benign salivary gland lesions is very high globally, but the figures for malignant lesions are comparatively low. This may be attributed to the inherent complexity of the salivary malignant pathologies, mostly related to their heterogeneous histological make-up. Certainly, the rarer entities would provide further diagnostic challenges. This article aims to provide a thorough but concise account of the challenges in routine salivary cytology in obtaining a near precise diagnosis and explores how the understanding of salivary histology can play an important role in increasing the diagnostic accuracy of the routine salivary FNAc reporting.     

Fine-needle aspiration cytology of mammary fibromatosis: Report of two cases

The purpose of this study is to evaluate cytologically two cases of mammary fibromatosis (MF). Prior to FNAC, clinical and mammographic suspicion of carcinoma and fibroadenoma were present. In both cases cytology disclosed the presence of numerous spindle cells admixed with epithelial cells. In the first case, carcinoma was excluded and the diagnosis of “spindle-cell proliferative lesion” was established. The second case was erroneously diagnosed as “cellular fibroadenoma” due to the presence of monolayered ductal epithelial groups and stromal tissue. In both cases local excision of the lesion was recommended. Although in a strict sense fibromatosis is a pure stromal lesion, the frequent presence of epithelial groups in the smears should raise a differential diagnosis with other more frequent mixed (epithelial and stromal) lesions such as fibroadenoma, cystosarcoma phyllodes, and metaplastic carcinoma. Due to the fact that clinically and mamographically MF is frequently confused with malignancy, preoperative recognition is essential since in many cases it would avoid unnecessary radical surgery. In this sense cytology offers very important preoperative information. Diagn. Cytopathol. 1997;17:363–368. © 1997 Wiley-Liss, Inc.     

Thymic epithelial cells as a diagnostic pitfall in the fine-needle aspiration diagnosis of primary mediastinal lymphoma

The cytologic diagnosis of primary mediastinal lesions is challenging due to the large number of lesions which may arise (i.e., lymphoma, thymoma, germ cell tumor), often with overlapping cytomorphologic features. We present an instructive case of primary mediastinal non-Hodgkin's large-cell lymphoma with sclerosis, entrapping thymic epithelium. Preoperative fine-needle aspiration yielded predominantly epithelial fragments and few lymphoid cells, leading to the cytologic misdiagnosis of thymoma. The entity of primary mediastinal large-cell lymphoma (LCL) is discussed and correlated with the cytologic features seen. In addition, histologic sections from 15 additional cases of primary mediastinal LCL were evaluated to determine the frequency with which significant numbers of epithelial fragments may be observed. Diagn. Cytopathol. 16:460–465, 1997. © 1997 Wiley-Liss, Inc.     

Fine-needle aspiration cytology of renal angiomyolipoma: Report of a case with immunocytochemical and electron microscopic findings

A case is presented in which the diagnosis of renal angiomyolipoma was made by computed tomography (CT)-guided, fine-needle aspiration cytology and the examination of a cell block. The tumor was characterized by epithelioid smooth muscle cells, blood vessels and fat in the cytologic material. The cytodiagnosis was further substantiated by positive staining of the epithelioid muscle cells for markers of muscle-specific actin, HMB45, and trace positivity for vimentin but not with S100 protein, desmin, or cytokeratin. Further studies for the recently described crystalloids were also performed by using the periodic-acid Schiff stain with and without diastase treatment and electron microscopy on the cytologic material. However, no such crystalloids were found. A preoperative cytologic diagnosis of renal angiomyolipoma was considered to be of value due to the difference in management between angiomyolipoma and a renal carcinoma, both of which can present as a renal mass on imaging. Diagn. Cytopathol. 1998;18:297–300. © 1998 Wiley-Liss, Inc.     

Fine-needle aspiration cytology and immunocytochemistry in the diagnosis of 24 gastrointestinal stromal tumors: a quick,reliable diagnostic method

The diagnosis of gastrointestinal stromal tumors (GISTs) is generally established on histopathologic examination of surgical specimens. Fine-needle aspiration (FNA), performed under the guidance of ultrasound or computed tomography, is being used with increasing frequency in an attempt to diagnose primary and/or metastatic GISTs before surgery. The present study was undertaken to characterize the cytological appearance of these tumors and to assess the role of cytology, together with immunocytochemistry (ICC), in the diagnosis of GISTs. Twenty-four GISTs diagnosed by FNA cytology at our institution have been reviewed. Immunocytochemical studies with c-kit and CD34 were performed in all cases on current or archival Papanicolaou-stained smears. All cases stained with c-kit, and 19 reacted with CD34. Cytomorphology and immunocytochemical characteristics are discussed. Our results confirm the utility of FNA together with ICC in the diagnosis of primary and/or metastatic GISTs.     

Poorly-differentiated adenoid cystic carcinoma: Cytologic appearance in fine-needle aspirates of distant metastases

Adenoid cystic carcinoma (ACC) is a primary salivary-gland neoplasm which typically yields characteristic cytomorphology upon fine-needle aspiration (FNA). We report on the FNA findings of a case of ACC metastatic to the liver which demonstrated a predominantly solid, poorly-differentiated pattern, an unusual but well-recognized subtype associated with a poor clinical outcome. The FNA findings in 7 additional cases of ACC metastatic to distant sites were also reviewed, with 4 cases displaying a prominent poorly-differentiated component. These findings suggest that, although not commonly recognized in salivary-gland FNAs, the poorly-differentiated pattern of ACC does occur in metastatic deposits and should be recognized as such, thereby preventing a needless search for a second primary malignancy. Diagn Cytopathol 1996;15: 296–300. © 1996 Wiley-Liss, Inc.