1. Confident recognition is often possible even in scanty samples.

2. Small cells, slightly larger than lymphocytes, in loosely associated groups in sputum, or dispersed in liquid-based preparations, washings and lavages.

3. Scanty cyanophilic cytoplasm, leading to nuclear moulding.

4. Coarse “salt and pepper” or dense chromatin. Nucleoli inconspicuous.

5. Small foci of necrosis.

6. Cells are larger in bronchial brushings and may show crush artefact.

7.Squamous metaplasia is often present (smoking association).

                

Distinguishing carcinoid tumor from small cell carcinoma of the lung: correlating cytologic features and performance in the College of American Pathologists Non-Gynecologic Cytology Program.Arch Pathol Lab Med. 2005 May;129(5):614-8. CONTEXT: The cytologic features of carcinoid tumor of the lung are well described. Nevertheless, some carcinoids may be difficult to distinguish from small cell carcinomas. OBJECTIVE: To correlate the cytologic features of individual cases of carcinoid tumor of the lung in fine-needle aspiration specimens in the College of American Pathologists Non-Gynecologic Cytology Program with the frequency of misclassification as small cell carcinoma. DESIGN: We reviewed 1100 interpretations from 26 different cases of carcinoid tumor in lung fine-needle aspiration specimens in the College of American Pathologists Non-Gynecologic Cytology Program and correlated the cytologic features with the performance in the program. RESULTS: Cases were divided into those that were frequently misclassified as small cell carcinoma (at least 20% of the responses, 19 cases) and those that were infrequently misclassified as small cell carcinoma (<10% of all responses, 7 cases). All cases had areas with classic features of carcinoid tumor. Cases were reviewed independently by 3 cytopathologists specifically looking for cytologic features that might be responsible for misclassification as small cell carcinoma. All 7 cases that were infrequently misclassified consisted of numerous monotonous well-preserved tumor cells that were either entirely round or were a mixture of round and spindle-shaped cells. Six of 7 cases showed a prominent streaming vascular pattern with tumor cells attached to the endothelial cell core. In contrast, cases that were frequently misclassified had 1 of 6 patterns that were not seen in cases that were rarely misclassified. These 6 patterns were: (1) poorly preserved and pale-staining cells with fine chromatin and a suggestion of molding (5 cases); (2) numerous large, well-preserved, spindle-shaped cells (2 cases); (3) numerous cells varying markedly in both size and shape (both round and spindle-shaped cells), with a common finding of degenerated, smudgy, small round and spindle-shaped cells (9 cases); (4) hypocellular specimens (8 cases); (5) obscuration of cells by blood (2 cases); and (6) tumor cells present predominantly in groups, with few isolated cells (8 cases). In none of these cases were mitoses or true necrosis identified. CONCLUSIONS: Frequent misclassification of carcinoid tumor as small cell carcinoma in lung fine-needle aspiration specimens in this program correlates strongly with specific cytologic features, some of which are common in small cell carcinoma (fine chromatin, molding, smudgy chromatin) and others that are not (spindle-shaped cells). In addition, hypocellular specimens or specimens with cellular obscuration performed poorly, along with specimens exhibiting absence of the commonly described carcinoid feature of streaming vascularity. Awareness of these patterns may aid in avoiding misdiagnosis. Small cell carcinoma versus other lung malignancies: diagnosis by fine-needle aspiration cytology.Cancer. 2000 Oct 25;90(5):279-85 BACKGROUND: When a diagnosis of small cell carcinoma is reached in a patient with a lung mass, a surgical treatment approach is no longer considered and chemotherapy becomes the treatment of choice. The aim of this study is to compare the diagnostic accuracy of fine-needle aspiration cytology in the diagnosis of small cell carcinoma with the diagnoses of other lung malignancies. The capacity of this technique to distinguish between these two categories is assessed. METHODS: Two hundred fifty-nine consecutive transthoracic fine needle aspirations of lung tissue from 235 patients with histologic diagnosis of malignancy were reviewed. The aspirates were performed over a 10-year period at the University of Miami/Jackson Memorial Medical Center, Miami, Florida. Two hundred and forty-two fine-needle aspirations from 221 patients yielded satisfactory smears and were included in the study. Fourteen patients were excluded. The cytologic diagnoses were classified into 5 categories: 1) small cell carcinoma (18 smears, 7%); 2) other lung malignancies (158 smears, 65%); 3) suspicious for malignancy (19 smears, 8%); 4) inflammatory process (7 smears, 3%); and 5) negative for malignancy (40 smears, 17%). RESULTS: The histologic diagnoses were divided into two groups: small cell carcinomas (29 smears, 12%), and other lung malignancies (213 smears, 88%). The efficiency of fine-needle aspiration cytology in the diagnosis of these two groups was 96% versus 88%, respectively, with an equal specificity of 100%, and a sensitivity of 67% versus 81%. Once the diagnosis of malignancy was established, fine-needle aspiration cytology was found to be highly accurate in distinguishing small cell carcinoma from other neoplasms. CONCLUSION: We conclude that fine-needle aspiration cytology of the lung is an accurate diagnostic tool for the diagnosis of lung malignancies and is an excellent technique for distinguishing small cell carcinoma from other malignant neoplasms. It can be used with confidence to select treatment modalities and to avoid unnecessary surgeries in patients with lung malignancies. Detection of large cell component in small cell lung carcinoma by combined cytologic and histologic examinations and its clinical implication.Cancer. 1992 Aug 1;70(3):599-605. BACKGROUND. In the classification recently proposed by the Pathology Committee of International Association for the Study of Lung Cancer, small cell lung carcinoma (SCLC) was divided into three subtypes: pure SCLC, mixed small cell/large cell carcinoma (mixed SC/LC), and combined SCLC. METHODS. To examine the clinical utility of this classification, histologic specimens, cytologic specimens obtained by brushing or fine-needle aspiration, and sputum cytologic specimens from 430 patients with SCLC were reviewed. RESULTS. When the subtype of SCLC was determined from the biopsy specimen, cytologic specimen obtained by brushing or fine-needle aspiration, and sputum cytologic specimen, the frequency of mixed SC/LC was 25 of 299 (8.4%), 75 of 400 (18.8%), and 8 of 232 (3.4%), respectively. Whatever the diagnostic method, patients with mixed SC/LC showed a poorer response to treatment and worse prognosis than those with pure SCLC: a median survival of 144 days versus 285 days when classified with the use of biopsy specimens; 160 days versus 275 days with cytologic specimens obtained by brushing or fine-needle aspiration; and 47 days versus 259 days with sputum cytologic specimens, respectively. CONCLUSIONS. These findings showed that mixed SC/LC should be separated from pure SCLC as a distinctive group and that cytologic studies of specimens obtained by brushing or fine-needle aspiration were sensitive and useful procedures for this purpose. Small-cell carcinoma of the lung. Cytological, roentgenologic, and clinical findings in a consecutive series diagnosed by fine-needle aspiration biopsy.Radiology. 1976 Nov;121(2):269-74. Small-cell anaplastic carcinoma was diagnosed cytologically in 54 of 2,726 consecutive transthoracic fine-needle aspiration biopsies. Histological material was available in 31 cases (28 anaplastic small-cell carcinomas, 1 carcinoid tumor, 1 adenocarcinoma, and 1 reticulum-cell sarcoma). Fine-needle aspiration cytology is reliable enough to permit a definite diagnosis of small-cell carcinoma, especially when combined with the roentgenograms and clinical findings.