Cytopathologic diagnosis of neuroendocrine neoplasia can be made by examining a variety of specimens obtained from several body sites that represent both exfoliative and aspiration cytopathology. Frequently received specimens include fine needle aspiration (FNA) biopsies and the specimens from the respiratory tract, especially for the diagnosis of pulmonary small cell neuroendocrine carcinomas. Table 2.1 lists various types of nongynecologic specimens with possible diagnostic entities pertaining to neuroendocrine neoplasia. Table 2.2 lists common sites for aspiration biopsy specimens.
Regardless of the specimen type, proper handling, optimal cytopreparatory techniques, and staining are absolutely essential and critical for rendering a meaningful diagnosis in the best interest of the patient. Cytopreparation is the crux of cytopathology. Its importance cannot be overemphasized. Expertise of the cytopathologists or the skills of cytotechnologists are of no use if they have to evaluate poorly prepared and poorly stained preparations. It leads to sheer frustration, especially when the cellular material is more than adequate but definite diagnosis cannot be offered as a result of suboptimal preparation. Poor cytopreparations may also lead to misinterpretations resulting in both false-positive and false-negative diagnosis.
Unlike surgical pathology, where the histologic preparation (fixation, processing, and staining) is standardized, cytopathology laboratories utilize several different modalities for cytopreparatory techniques. There are considerable variations involving each and every step of cytopreparatory technique, from specimen submission to the final product (stained smear).
Specimens for cytologic evaluation include fine needle aspirates, body cavity fluids, specimens obtained by various endoscopic procedures such as bronchoscopy (smears from brushings, washings, or bronchoalveolar lavage), cervical smears, urines, urinary bladder washings, etc.
The specimens may be submitted, fresh and unfixed, fresh but collected in non-alcohol-based fluid medium such as balanced salt solution, or fixed in various grades of alcohols, or in commercial liquid fixatives such as Saccomanno or Cytolyte and Cytorich.
The specimens may also be submitted as prepared smears, either from the fine needle aspirates prepared at the site of procedure or the direct smears prepared from the endoscopic brushings or from scrapings of the lesions. The smears (cell spreads) are also prepared from the sediments of centrifuged liquid specimens such as bronchial brush rinsings, bronchial washings, bronchoalveolar lavage, body cavity fluids, cyst aspirates, or needle rinses following fine needle biopsy procedures.
Monolayered thin cell spreads are ideal for cytopathologic evaluation. Thick, bloody, uneven smears are unsatisfactory. Several techniques are described for preparing the smears; personal preference dictates the technique used, quality of which is extremely variable.
Liquid specimens such as body cavity fluids may be processed by conventional methods or with liquid-based technology. Specimens collected in alcohol-based fixatives are difficult to smear. Specimens collected in Saccomanno fixative have produced good results in terms of cell block preparations. Smears are difficult to make, as the fixed cellular material cannot be spread evenly if at all. The exception is sputum collected in Saccomanno fixative, which is processed by an entirely different technique.
The prepared smears are subsequently fixed either by air-drying or fixed in alcohols of various strengths or by using commercial spray fixatives depending on the choice of stains. Prompt wet fixation is required for Papanicolaou stain to bring about the nuclear details, for example, the salt-pepper chromatin of neuroendocrine tumor cell nuclei (Fig. 2.1A). In the author’s experience, this nuclear pattern is best demonstrated with spray-fixed, Papanicolaou-stained preparations. Slightest delay in fixing the smears for Papanicolaou staining will result in pale, swollen nuclei making the cytologic interpretation difficult (see Fig. 3.59). Compact dark-staining nuclear chromatin, karyorrhexis, and nuclear molding are also best visualized in spray-fixed Papanicolaou-stained preparations (Fig. 2.1B).
TABLE 2.1. TYPES OF CYTOLOGIC SPECIMENS FOR THE DIAGNOSIS OF NEUROENDOCRINE TUMORS: EXFOLIATIVE CYTOPATHOLOGY
The cell blocks are usually prepared, specimen permitting. The term cell block refers to the examination of the sediment, blood clots, or grossly visible flecks of tissue from cytologic specimens that are processed by paraffin embedding and staining by hematoxylin and eosin. Small tissue flecks must be wrapped in tissue paper and then placed in the cassette. Cell blocks are complementary to the smears and allow extra slides to be cut for ancillary tests when special stains are anticipated. When submitting a cell block for processing, it is prudent to place a note in the cassette for the histotechnologist to cut extra sections for immunostains, especially when neuroendocrine neoplasia is suspected.
Several techniques exist for processing the cell blocks including the commercial cell block processor. Most neuroendocrine neoplasms require confirmation of the diagnosis via immunostains. Cell blocks are best suited for the purpose. In the absence of the cell blocks, Papanicolaou-stained smears can certainly be processed for immunostains.
The staining methods used in cytopathology laboratories are varied as well. In general, Papanicolaou stain is utilized for exfoliative cytopathology, for example, nongynecologic specimens. However, Papanicolaou, hematoxylin and eosin, and Romanowsky stains are all used for fine needle aspirates. The choice of stain depends on personal preference. Several variations of Romanowsky stains are available. The most commonly used one is commercially available Diff-Quik. Papanicolaou stain is relatively standardized. However, its quality control must be carried out on a daily basis.
TABLE 2.2. TYPES OF CYTOLOGIC SPECIMENS FOR THE DIAGNOSIS OF NEUROENDOCRINE TUMORS: FNA BIOPSY
