Cytologic appearances in invasive lobular carcinoma of the breast. A study of 21 cases

OBJECTIVE: To examine the fine needle aspiration cytologic features of invasive lobular carcinoma of breast and to discuss problems that may occur in cytodiagnosis. STUDY DESIGN: Fine needle aspiration cytologic smears from 21 cases of invasive lobular carcinoma (ILC) of breast were subjected to detailed cytomorphologic analysis. Features studied included pattern of cells, size of cells, nuclear placement, pleomorphism, presence of intracytoplasmic lumina (ICL) and signet ring cells. RESULTS: Cellularity was generally moderate or high, and the pattern was predominantly or partly dissociated in 86% of cases. Rosettelike pattern was discerned in alveolar-type ILC. Cell size was usually small or intermediate, with nuclei placed eccentrically in most cases. ICLs with or without signet ring cells were present in 12 cases (57%). CONCLUSION: A cytologic picture consisting of predominantly dissociated small or intermediate-sized tumor cells with eccentric nuclei, with some of the cells showing ICLs, is highly suggestive of ILC. Indian file pattern, another characteristic feature of ILC, is, however, focal and inconsistent. Variant patterns of ILC may show other cytologic features, such as rosettelike pattern (alveolar variant of ILC) or large cell pattern (pleomorphic variant of ILC) and may consequently be difficult to categorize on cytologic smears.     

Hepatic metastases from the spindle cell variant of medullary thyroid carcinoma: report of a case with diagnosis by fine needle aspiration biopsy.

BACKGROUND: The liver is a common site of neuroendocrine tumors (NTs) metastatic from primaries in the gastrointestinal tract, pancreas, biliary system and lungs. Medullary thyroid carcinoma (MTC) is also a potential source of metastases of NTs. Their metastases to the liver are frequent and can appear several years after the primitive tumor. Although a wide variety of cytomorphologic features are normally exhibited by MTC in smears, a spindle-shaped cell pattern can predominate, complicating the correct interpretation of a metastasis. CASE: A 63-year-old man presented with multiple liver nodules two years after a total thyroidectomy for MTC. Fine needle aspiration biopsy smears of the liver revealed neoplastic cells occurring in loose groupings or lying singly, most of them with a spindle shape and elongated nucleus with the characteristic "salt and pepper" chromatin pattern of a neuroendocrine tumor. Cytoplasmic dendritic processes and intranuclear inclusions were frequently seen. The cytomorphologic features of the tumor were essentially the same as those of the primary MTC. Immunoreactivity for calcitonin confirmed the diagnosis. CONCLUSION: In fine needle aspiration biopsy of liver masses, knowledge of the spindle pattern of the NT is important in order to achieve a correct diagnosis when metastases are the first manifestation of an occult primary tumor. Among neuroendocrine tumors, MTC must be included in the differential diagnosis.     

Cytomorphologic patterns in papillary cystic variant of acinic cell carcinoma of the salivary gland

OBJECTIVE: To study the cytomorphologic profile of the papillary and cystic variant of acinic cell carcinoma (ACC-PCV) of the salivary glands. STUDY DESIGN: We studied 6 aspirates from 5 cases of ACC-PCV. RESULTS: All the cases had varied cytomorphologic features depending upon the degree of vacuolation of cells. However, common to all was a papillary pattern and a cystic fluid background with or without mucin blobs; that led to misdiagnosing the tumor as mucoepidermoid carcinoma on 2 occasions. The smears showed papillary fragments, sheets or clusters of vacuolated/histiocyte like cells and granular cells. The histiocytelike cells resembled macrophages, with finely vacuolated cytoplasm and an eccentrically placed nucleus with frequent binucleation. Vascular cores were seen in a few aspirates. The granular cells were similar to those seen in the usual acinic cell carcinoma but were smaller. The tumor did not show any acinar pattern and lacked naked nuclei in the background. In 4 aspirates finely distributed, brown hemosiderin pigment was detected in the vacuolated cells. CONCLUSION: ACC-PCV is papillary and cystic and hence is often not recognized as acinic cell carcinoma. However, papillary fragments of vacuolated cells or histiocytelike cells and granular cells are clues to the diagnosis.     

Nuclear DNA content, cytomorphologic features and clinical characteristics of small cell carcinoma of the lung

The relationship between the cytomorphologic features, the nuclear DNA patterns and the clinical prognosis of patients with small cell carcinoma of the lung was studied. In cases in the long-survival group (greater than or equal to 24 months), bronchial brushing smears contained a relatively high frequency of nuclei with large, irregular shapes and finely granular chromatin patterns, in comparison with patients in the short-survival group (less than or equal to 9 months); the correlation was not statistically significant, however. The incidence of cells with round or oval nuclei and finely granular chromatin patterns was higher in patients whose cells had hyperdiploid DNA patterns than for patients whose cells had near-diploid patterns; again, the difference was not statistically significant. Patients whose tumor cells had hyperdiploid DNA patterns had significantly shorter survival times than did patients whose tumor cells had near-diploid patterns. These results indicate that (1) judging the nuclear DNA pattern from the cytomorphologic features of small cell carcinoma is unreliable and (2) the nuclear DNA patterns are related to the clinical prognosis of patients with small cell carcinoma of the lung.     

The positive pleural effusion. A retrospective study of cytopathologic diagnoses with autopsy confirmation.

We performed an investigation focusing on the distribution of tumor types responsible for positive pleural effusions in 143 patients who died of malignancy and underwent autopsy. The principal malignant tumors were lung carcinoma (41 cases, 51.2%) and pleural mesothelioma (23 cases, 28.7%) in males and breast carcinoma (24 cases, 38.2%) and lung carcinoma (13 cases, 20.6%) in females. Histologically, most of the cases belonged to the adenocarcinoma category. The first morphologic diagnosis was a cytologic one in 86 cases (60.1%), especially regarding lung cancer. In breast cancer a positive pleural effusion always preceded recurrent disease with a rapidly progressive course, even a long time after the initial surgery. The results of this study, based on both cytomorphologic features and postmortem data on the tumor sites, may be a useful working framework for the cytologist dealing with a positive pleural effusion.     

Cytomorphologic features of a polymorphous low grade adenocarcinoma of the palate. A report of 2 cases with immunocytochemistry

BACKGROUND: Polymorphous low grade adenocarcinoma (PLGA) is a histologically low grade tumor of minor salivary gland origin. It is important to differentiate PLGA from other salivary gland tumors with myoepithelial differentiation, such as pleomorphic adenoma, adenoid cystic carcinoma and epithelial myoepithelial carcinoma. Here we report 2 cases of PLGA originating in the palate and describe the cytomorphologic and immunocytochemical features. CASES: The patients were a 55-year-old woman and a 63-year-old man. Both presented with a mass in the palate. Clinically the mass appeared malignant, and resection was performed. Cytologically the tumor cells were composed of sheet clusters, pseudopapillary epithelial clusters, naked cells and stromal components. Immunocytochemically the tumor cells showed strong expression of carcinoembryonic antigen (CEA) and vimentin. CONCLUSION: PLGA may be difficult to distinguish from other salivary gland tumors with myoepithelial differentiation. However, the cytopathologist should be aware of the distinctive cytomorphologic features of PLGA, demonstrating immunopositivity to CEA and vimentin.     

Glassy cell carcinoma of the uterine cervix. Cytologic features and expression of estrogen and progesterone receptors

OBJECTIVE: To identify the cytomorphologic features and investigate the expression of estrogen receptor (ER) and progesterone receptor (PR) in glassy cell carcinoma (GCC) of the uterine cervix. STUDY DESIGN: A retrospective analysis of nine GCCs encountered at Korea Cancer Center Hospital between January 1990 and April 1999 was undertaken. The cervical smears were obtained prior to histologic diagnosis of GCC. The cytomorphologic and clinical features were reviewed, and the expression of ER and PR was investigated immunohistochemically on histologic sections. RESULTS: Smears of GCC were hypercellular and remarkably cohesive. The tumor cells were large and characterized by abundant granular cytoplasm, distinct cell membranes and round to polygonal, large nuclei with prominent nucleoli. In the background tumor diathesis and numerous inflammatory cells containing eosinophils were present. The inflammatory cells (mainly eosinophils) were intimately associated with tumor cells to form "granuloepithelial complex." Immunohistochemically, ER was identified in two of the nine cases and PR in one of them. CONCLUSION: Cytology of GCC has characteristic features that differ from those of other carcinomas or atypical reparative cells. Although there are deceptive mimics of GCC, the characteristic cytologic findings should prompt a diagnosis of GCC. ER and PR positivity was found in two cases (22%) and one case (11%), respectively, of GCC, suggesting that this tumor might be hormonally responsive.     

Cytologic features of pilocytic astrocytoma in cerebrospinal fluid specimens

OBJECTIVE: To illustrate the cytomorphologic features of pilocytic astrocytoma (PA) in cerebrospinal fluid (CSF) samples. STUDY DESIGN: A search of records from 1965 to 2001 was performed to identify all patients with a diagnosis of PA in whom CSF samples were examined. Slides from CSF samples originally reported as atypical, suspicious or positive were reviewed and the cytomorphologic features assessed. RESULTS: Two hundred ninety-three patients with a diagnosis of PA were identified. Of these, 44 had a total of 65 cytologic preparations of CSF. In 34 patients (77.2%) the CSF cytology was negative, in 5 (11.4%) either atypical or suspicious, and in 5 (11.4%) positive for neoplastic cells. The tumors in the 5 positive cases arose in the cerebellar hemispheres (2), cerebellar vermis (1), thalamus (1) and tectum with extension into the fourth ventricle (1). All positive samples were hypercellular, with an average of 5 cell clusters per case (range, 3-11). The clusters were composed of cohesive epithelioid cells with a mean of 8 cells per cluster. In addition, some cases had scattered, isolated, single cells. These single neoplastic cells had prominent, hairlike cytoplasmic processes. The cells in clusters appeared epithelioid, with oval nuclei, mild nuclear pleomorphism, finely or slightly coarsely granular chromatin and cobweblike cytoplasm. CONCLUSION: The cytomorphologic features of PAs recapitulate their histologic characteristics. The tumor cells are recognizable in CSF samples and readily distinguishable from histiocytes and ependymal cells.     

Pheochromocytoma. Cytologic findings on intraoperative scrape smears in five cases

BACKGROUND: There have been few studies describing the cytology of adrenal pheochromocytoma (PC). Although fine needle aspiration (FNA) for a preoperative diagnosis of PC is generally considered a contraindication, this tumor can be an unsuspected finding in adrenal FNA performed for other reasons. STUDY DESIGN: Scrape cytology smears prepared in five cases of PC were examined for different cytomorphologic features. The results were correlated with the corresponding permanent histologic sections. RESULTS: Previously described features, like cellular smears showing cells with abundant, poorly defined fragile cytoplasm, bare nuclei, anisonucleosis, "salt and pepper" chromatin, variable nucleoli and few ganglion cell-like cells, were noted. In addition, several previously unreported cytologic features were observed: (1) loosely cohesive PC cells along a ramifying, delicate central core; (2) intracytoplasmic microvesicular (not hyaline/homogeneous) globules; and (3) different arrangements of capillary-stroma and PC cells (Zellballen pattern; empty capillary rings; stroma with adherent, intact PC cells or fragments of disrupted PC cell cytoplasm). CONCLUSION: The cytologic appearance of PC may resemble that of other neuroendocrine tumors; however, it can be diagnostic when combined with proper clinical data and ancillary tests.     

Adenoid cystic carcinoma of the external auditory canal. A case report with diagnosis by fine needle aspiration

BACKGROUND: Although the cytologic findings of adenoid cystic carcinoma have been reported frequently, fine needle aspiration diagnosis of adenoid cystic carcinoma of the external auditory canal has not been reported before in the English-language literature. CASE: A 70-year-old female presented with a mass occluding the external auditory canal. Fine needle aspiration cytology was performed. The smears showed hyaline globules surrounded by tumor cells. The tumor cells had uniform, round, hyperchromatic nuclei, visible nucleoli and little cytoplasm. Based on these cytomorphologic features, diagnosis of adenoid cystic carcinoma was rendered and then confirmed by histopathologic examination. CONCLUSION: This is the first cytologic report of adenoid cystic carcinoma of the external auditory canal, a rare site for this tumor.     

Cytomorphologic features of the rare epithelial-myoepithelial carcinoma of the salivary gland

The cytomorphologic features of an epithelial-myoepithelial carcinoma arising in the submandibular gland are reported. The aspiration smears were cellular, with two cell types present: dark cells showing attempted gland formation and clear cells with vacuolization. The clear cells frequently formed globular masses and had indistinct cytoplasmic membranes. These globular masses of clear cells were usually adjacent to the fragments of dark cells. A striking feature was the presence of numerous naked nuclei.     

Islet cell tumor of the pancreas: increasing diagnosis after instituting ultrasonography-guided fine needle aspiration

OBJECTIVE: To review the clinical and cytomorphologic features of pancreatic islet cell tumors (ICT). STUDY DESIGN: Computer search identified patients with pancreatic ICT diagnosed by fine needle aspiration biopsy (FNAB) between January 1995 and December 2003. Clinical, radiographic, and cytomorphologic findings were reviewed. RESULTS: Thirty-eight patients (19 men, 19 women; median age 60 years, range 30-82) with ICT were identified; 30 were diagnosed through endoscopic ultrasonography (EUS)-FNAB and 8 through computed tomography (CT)-guided FNAB. Smears of 37 specimens had adequate cellularity. Most were highly cellular with bloody backgrounds. No major differences were observed between specimens obtained by EUS-FNAB or CT-FNAB. Radiographically, 20 tumors measured 1-5 cm, 7 were > 5 cm and 4 < 1 cm. Twenty-two patients underwent tumor resection. CONCLUSION: Newer radiography and biopsy techniques to detect and examine smaller pancreatic masses have increased the number of pancreatic ICT diagnoses at our institution. The distinctive cytomorphologic features of pancreatic ICT make it reliably diagnosable by FNAB.     

Endoscopic ultrasound-guided fine needle aspiration cytology of intraductal papillary mucinous tumor of the pancreas. A case report

BACKGROUND: Intraductal papillary mucinous tumor (IPMT) of the pancreas is a recently proposed pancreatic tumor entity with a peculiar clinical and pathologic profile. It presents with symptoms that are mostly attributed to the mass effect of the tumor. However, a long history of diabetes mellitus and/or chronic pancreatitis is usually noted. It is thought that IPMT has better prognosis than the usual pancreatic ductal adenocarcinoma and its early identification is important. On imaging studies these neoplasms appear usually as multiloculated, cystic tumors that cannot be easily differentiated from other cystic pancreatic neoplasms. CASE: A 73-year-old, white woman with recent symptoms related to bile duct obstruction and diabetes mellitus and a long history of "chronic pancreatitis" was found to have a pancreatic mass on computed tomography. Endoscopic ultrasound-guided fine needle aspiration of the pancreatic mass and dilated pancreatic duct was performed. Cytopathologic examination of the aspirated material revealed large cells with abundant, eosinophilic cytoplasm arranged singly or occasionally in large sheets with complex papillary fragments. Occasional goblet cells or cells with cytoplasmic mucin-containing vacuoles were also noted within the tumor tissue fragments. The nuclei were large, with nuclear size variability and prominent nucleoli. Copious amounts of mucin and numerous muciphages were noted in the background. A diagnosis of "cystic mucinous tumor, cannot rule out invasion," was entertained. The patient underwent partial pancreatectomy. The histologic features of the resected specimen were consistent with IPMT, with focal areas suggestive of early stromal invasion. CONCLUSION: The cytologic features encountered in the aspirate of this tumor are highly suggestive of IPMT and can help differentiate it from other pancreatic tumors with mucin production, such as the classic mucinous cystic neoplasm and the more common ductal carcinoma.     

Cytologic features of islet-cell tumors

Although a number of reports have demonstrated the accuracy of fine needle aspiration (FNA) in the diagnosis of nonendocrine pancreatic carcinomas, the cytomorphology of islet-cell tumors (pancreatic endocrine tumors) is not well defined. This paper describes the cytologic features of three histologically confirmed cases of islet-cell tumors. The three tumors occurred in one man and two women, who were 63, 64 and 70 years of age, respectively. Each patient underwent FNA of pancreatic mass with computed body tomography guidance. The aspirates contained large numbers of tumor cells in two cases and a smaller number in one case. The cells, distributed singly and in small groups, were small and round or polygonal, with scant to more often abundant, dense or granular cytoplasm. The nuclei were often located eccentrically and were round to oval, with smooth nuclear borders and finely stippled chromatin. Many nuclei contained a single nucleolus. Multinucleated cells were present and generally contained two or three nuclei. Although the diagnosis of islet-cell tumors in fine needle aspirates is difficult, the cytomorphologic features of these tumors are sufficiently distinctive to suggest the diagnosis, especially when a relatively monomorphic population composed predominantly of single cells is present.     

Fine needle aspiration cytology of a low grade myxoid renal epithelial neoplasm: a case report

BACKGROUND: Recently, several case reports have described a rare but distinct subtype of renal tumor, referred to as a "low grade renal epithelial neoplasm," that appears to have a better prognosis than conventional renal cell carcinoma does. This report describes the cytologic features of this tumor as determined by fine needle aspiration (FNA) biopsy. CASE: A 53-year-old woman with a history of lymphoma had a renal mass incidentally discovered on an abdominal computed tomographic scan performed for lymphoma restaging. Results of an FNA biopsy showed relatively uniform, medium-sized tumor cells with moderate amounts of finely vacuolated or wispy cytoplasm and indistinct cell borders. The nuclei were primarily round with coarse chromatin and had prominent nucleoli. In the cell block preparation, the tumor cells showed a tubular architecture and an abundant myxoid matrix. The patient underwent a partial nephrectomy. The tumor was classified as a low grade myxoid renal epithelial tumor. CONCLUSION: This unusual kidney tumor appears to have distinctive cytomorphologic features, including a uniform population of epithelial cells with round nuclei, an abundant myxoid matrix and tubular architecture.     

Thin-layer cytology findings of small cell carcinoma of the lower female genital tract. Review of three cases with molecular analysis

OBJECTIVE: To describe the thin-layer cytology findings of small cell carcinoma of the low female genital tract, with histologic correlation and human papillomavirus (HPV) genotyping. STUDY DESIGN: The authors reviewed the clinical findings, thin-layer cytology and histologic features of small cell carcinoma of the lower female genital tract (cervix or vagina) occurring in three postmenopausal Chinese women at Pamela Youde Nethersole Eastern Hospital, Hong Kong, over a four-year period, from January 1998 to December 2001. Molecular techniques for HPV screening and genotyping using the polymerase chain reaction and restriction fragment length polymorphism were employed on the cytologic specimens. RESULTS: The thin-layer preparations were of moderate to high cellularity. There were loose aggregates of or isolated small round cells with a high nuclear/cytoplasmic ratio, thin but irregular nuclear membrane, hyperchromatic nuclei, inconspicuous nucleoli and scanty cytoplasm. Tumor cell cannibalism was commonly found. Small groups of tumor cells with nuclear molding were noted. There was also obvious tumor diathesis in the background. The necrotic debris was admixed with isolated small round cells, apoptotic bodies and nuclear dust. Associated koilocytosis or squamous intraepithelial lesions were not seen. Histologic examination of the tumor biopsies showed classic features of small cell carcinoma associated with squashing artifacts and vascularized stroma. Molecular analysis revealed the presence of HPV DNA (either type 18 or 16) in all the three liquid-based cytology samples. CONCLUSION: While the cytomorphologic features of small cell carcinoma of the cervix or vagina in thin-layer preparations are slightly different from those in conventional smears, due mainly to the absence of smearing effect, recognition of the subtle but characteristic appearance can enhance the accuracy of the cytologic diagnosis. The association between HPV and primary small cell carcinoma of the lower female genital tract was confirmed by this study.     

Cytologic evaluation of low grade transitional cell carcinoma and instrument artifact in bladder washings

OBJECTIVE: To identify key cytologic features for the separation of low grade transitional cell carcinomas (TCCs) from nonneoplastic lesions in bladder washings. STUDY DESIGN: The cytomorphologic features of 95 bladder washing specimens showing papillary fragments, which included 50 low grade TCCs and 45 nonneoplastic lesions, were reviewed retrospectively. RESULTS: Bladder washings from low grade TCCs showed papillary and irregular groups of cells with ragged borders, cytoplasmic homogeneity and subtle nuclear changes, such as increased nuclear/cytoplasmic ratio and irregular nuclear border. Bladder washings after instrumentation from nonneoplastic lesions of the bladder showed cellular specimens with cohesive, ball-shaped and papillary clusters with smooth borders lined with a denser-staining cytoplasmic collar. Reactive urothelial cells often displayed loose aggregates with irregular borders but no cytoplasmic collar. CONCLUSION: In bladder washing cytology, nuclear changes and cytoplasmic homogeneity play a major role in the diagnosis of carcinoma.     

Fine needle aspiration cytology of lobular breast carcinoma. Comparison with other breast lesions

OBJECTIVE: To analyze the detailed cytomorphology of lobular breast carcinoma and to compare the cytologic smears of benign, borderline and infiltrating duct carcinoma. STUDY DESIGN: Fine needle aspiration cytology (FNAC) smears of histopathologically proven infiltrating lobular carcinoma (ILC), infiltrating ductal carcinoma (IDC), borderline lesions and benign breast lesions were selected for study. Detailed cytomorphologic analysis of the smears was carried out on hematoxylin and eosin- and May-Grünwald-Giemsa--stained slides, and a comparison of results was done. The various cytologic features were also graded semi-quantitatively with the numerical score; logistic regression analysis was done. RESULTS: There were 25 cases of ILC, 30 of IDC, and 10 borderline and 18 benign lesions. Cytologic diagnosis of malignancy on FNAC smears of ILC was offered in 19 cases; of them, 2 cases were diagnosed as ILC. The remaining six cases were diagnosed as borderline (four) and benign lesions (two). Overall sensitivity in detection of malignancy in ILC cases was 76%. FNAC smears of ILC showed moderate (52%) to abundant (32%) cellularity. The cells of ILC were arranged both in clusters and in dissociation (72%). Individual cells were monomorphic (40%) to mildly pleomorphic (60%), and the cells were smaller. The cells showed a smooth, regular nuclear margin; bland chromatin; and indistinct nucleoli. Indian file arrangement was frequently observed (28%). Nuclear molding (28%) and intranuclear inclusions (16%) were also noted. Intracytoplasmic lumina were seen in occasional cases. Logistic regression analysis was carried out, and a comparison between lobular carcinoma and ductal carcinoma, and borderline and benign lesions was done. Logistic regression analysis of cytomorphologic features showed that cellularity and nuclear margin irregularities were the two most important features to distinguish ILC from IDC. In comparison to borderline lesions, cell dissociation was more common in ILC. The salient cytologic features that helped to distinguish ILC from benign lesions was cell size, cellularity, cell uniformity and chromatin pattern. CONCLUSION: There are overlapping cytologic features between ILC, IDC and borderline breast lesions on FNAC smears. Logistic regression analysis may be helpful in this regard.     

Cytomorphologic and immunocytochemical characteristics of reactive renal tubular cells in renal glomerular disease

OBJECTIVE: To investigate the morphologic characteristics and immunocytochemical reaction to vimentin of the reactive renal tubular cells (RRTCs) in renal glomerular disease. STUDY DESIGN: We prospectively evaluated the urine cytology of renal glomerular disease in 40 patients who underwent renal biopsy. The cytology and renal biopsy specimens were analyzed for vimentin immunostaining. RESULTS: A total of 40 urine samples from the 40 patients were cytologically analyzed, and RRTCs were found in 25 samples (25 of 40, 62.5%). These RRTCs showed clear or vacuolated cytoplasm, intracytoplasmic pigmented granules (hemosiderin or lipofuscin) and large nuclei with round to irregular nuclear contours and prominent nucleoli. These cells were seen singly and in acinar clusters. Occasionally RRTCs were embedded in a cast (RRTC cast). Immunocytochemicalstudy revealed RRTCs to be positive for vimentin (25 of 25, 100%). CONCLUSION: Frequently observed characteristic cytomorphologic features of RRTCs included RRTC cast, acinar cluster, vacuolated cytoplasm and intracytoplasmic pigmented granules. A diagnosis of RRTCs can be suggested based on these cytomorphologic features. However, a definitive diagnosis will require immunocytochemical confirmation for vimentin.     

Peripheral T-cell lymphoma not otherwise specified vs. Hodgkin's lymphoma on fine needle aspiration cytology

OBJECTIVE: To study the morphologic features of peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS) on fine needle aspiration cytology (FNAC) smears and to identify cytomorphologic features that would delineate them from features of cases of Hodgkin's lymphoma (HL). CONCLUSION: Fourteen cases each of PTCL, NOS, and HL with adequate FNAC smears were retrieved. These cases were analyzed for 12 cytomorphologic features: presence of atypical lymphoid cells, percentage of large lymphoid cells, lymphoid cells with cleaved/indented nuclei, typical Reed-Sternberg (RS) cells, mononuclear cells with prominent eosinophilic macronucleoli, mononuclear cells with prominent nucleoli, histiocytes, eosinophils, plasma cells, polymorphonuclear leukocytes, vessels and perivascular clustering of atypical mononuclear/atypical lymphoid cells. Each of these features was evaluated for its presence or absence and was semiquantitated on a scale from 0 to +3. RESULTS: The presence of atypical lymphoid cells with a spectrum ranging from small to intermediate and large was seen exclusively in cases of PTCL. Lymphoid cells with cleaved or indented nuclei, endothelium-lined vessels with perivascular clustering of tumor cells and absence of typical RS cells, and mononuclear cells with prominent eosinophilic macronucleoli emerged as the parameters significant in not only diagnosing cases of PTCL, NOS, but also in their delineation from cases of HL. CONCLUSION: A careful analysis of cytomorphologic features can be useful in at least suggesting a diagnosis of PTCL and help to distinguish that diagnosis from HL, which the features may mimic. Immunophenotyping and molecular studies are important in arriving at a definitive diagnosis.