Clinical characteristics and outcomes of null-cell versus silent gonadotroph adenomas in a series of 1166 pituitary adenomas from a single institution.

OBJECTIVE: Nonfunctioning pituitary adenomas present without biochemical or clinical signs of hormone excess and are the second most common type of pituitary adenomas. The 2017 WHO classification scheme of pituitary adenomas differentiates null-cell adenomas (NCAs) and silent gonadotroph adenomas (SGAs). The present study sought to highlight the differences in patient characteristics and clinical outcomes between NCAs and SGAs. METHODS: The records of 1166 patients who underwent transsphenoidal surgery for pituitary adenoma between 2012 and 2019 at a single institution were retrospectively reviewed. Patient demographics and clinical outcomes were collected. RESULTS: Of the overall pituitary adenoma cohort, 12.8% (n = 149) were SGAs and 9.2% (n = 107) NCAs. NCAs were significantly more common in female patients than SGAs (61.7% vs 26.8%, p < 0.001). There were no differences in patient demographics, initial tumor size, or perioperative and short-term clinical outcomes. There was no significant difference in the amount of follow-up between patients with NCAs and those with SGAs (33.8 months vs 29.1 months, p = 0.237). Patients with NCAs had significantly higher recurrence (p = 0.021), adjuvant radiation therapy usage (p = 0.002), and postoperative diabetes insipidus (p = 0.028). NCA pathology was independently associated with tumor recurrence (HR 3.64, 95% CI 1.07-12.30; p = 0.038), as were cavernous sinus invasion (HR 3.97, 95% CI 1.04-15.14; p = 0.043) and anteroposterior dimension of the tumor (HR 2.23, 95% CI 1.09-4.59; p = 0.030). CONCLUSIONS: This study supports the definition of NCAs and SGAs as separate subgroups of nonfunctioning pituitary adenomas, and it highlights significant differences in long-term clinical outcomes, including tumor recurrence and the associated need for adjuvant radiation therapy, as well as postoperative diabetes insipidus. The authors also provide insight into independent risk factors for these outcomes in the adenoma population studied, providing clinicians with additional predictors of patient outcomes. Follow-up studies will hopefully uncover mechanisms of biological aggressiveness in NCAs and associated molecular targets.

Endothelial cell-specific molecule-1 as an invasiveness marker for pituitary null cell adenoma.

BACKGROUND: Endothelial cell-specific molecule-1 (ESM-1) is a biomarker associated with tumor progression in pituitary adenoma. We specifically focused on one type of pituitary adenoma, namely null cell adenoma (NCA) and evaluated the relationship between invasion and ESM-1 expression in both vascular endothelial and adenoma tissues. METHODS: Tissue samples from 94 patients with pituitary NCA were obtained through microscopic transsphenoidal resection. Tumor size and invasion were determined through preoperative magnetic resonance imaging. Immunohistochemical staining was performed to detect ESM-1 expression. ESM-1 index of ≥3 was defined as high expression. RESULTS: Signs of invasion were observed in 46 (47.9%) of the 94 patients. Significant differences were observed in the invasion state and maximum tumor diameter between high and low expression of ESM-1 in vascular endothelial tissues (both P < 0.05). Significant positive associations were noted between ESM-1 expression in vascular endothelial tissues and tumor invasion (P = 0.002) and tumor size (P = 0.020). However, only tumor size was associated with ESM-1 expression in adenoma tissues (P = 0.016). CONCLUSION: In NCA, a significant positive association between tumor invasion and ESM-1 expression was observed only in vascular endothelial tissues, suggesting that tumor progression occurs mainly through ESM-1-associated mechanism.

Clinical, pathologic, and imaging characteristics of pituitary null cell adenomas as defined according to the 2017 World Health Organization criteria: a case series from two pituitary centers.

PURPOSE: The 2017 World Health Organization classification of pituitary tumors redefined pituitary null cell adenomas (NCAs) by restricting this diagnostic category to pituitary tumors that are negative for pituitary transcription factors and adenohypophyseal hormones. The clinical behavior of this redefined entity has not been widely studied, and this is a major shortcoming of the classification. This study evaluated the imaging and clinical features of NCAs from two pituitary centers and compared them with those of gonadotroph adenomas (GAs). METHODS: Imaging, pathologic, and clinical characteristics of NCAs and GAs were retrospectively reviewed. Tumor immunohistochemistry was performed to confirm absence of adenohypophyseal hormones and pituitary transcription factor expression. RESULTS: Thirty-one NCAs were compared with 38 GAs. NCAs were more likely to invade the cavernous sinus (15/31 [48%] vs. 5/38 [13%], P = .003) and had a higher proliferative index (i.e., MIB-1 > 3%, 11/31 [35%] vs. 5/38 [13%], P = .04). Gross total resection was less likely in the NCA group (19/31 [61%] vs. 33/38 [87], P = .02). Progression-free survival was worse in the NCA cohort (5-year progression-free survival, 0.70 vs. 1.00; P = .011, by log-rank test). CONCLUSIONS: Compared with GAs, NCAs are more invasive at the time of presentation and have a more aggressive clinical course. This study provides evidence that NCAs represent a distinct clinicopathologic entity with behavior that differs adversely from that of GAs. This may inform clinical decision-making, including frequency of postoperative tumor surveillance and timing of adjunctive treatments.

Ikaros promotes rearrangement of TCR α genes in an Ikaros null thymoma cell line.

Ikaros is important in the development and maintenance of the lymphoid system, functioning in part by associating with chromatin-remodeling complexes. We have studied the functions of Ikaros in the transition from pre-T cell to the CD4(+) CD8(+) thymocyte using an Ikaros null CD4(-) CD8(-) mouse thymoma cell line (JE131). We demonstrate that this cell line carries a single functional TCR ß gene rearrangement and expresses a surface pre-TCR. JE131 cells also carry nonfunctional rearrangements on both alleles of their TCR α loci. Retroviral reintroduction of Ikaros dramatically increased the rate of transcription in the α locus and TCR Vα/Jα recombination resulting in the appearance of many new αßTCR(+) cells. The process is RAG dependent, requires switch/sucrose nonfermentable chromatin-remodeling complexes and is coincident with the binding of Ikaros to the TCR α enhancer. Furthermore, knockdown of Mi2/nucleosome remodeling and deacetylase complexes increased the frequency of TCR α rearrangement. Our data suggest that Ikaros controls Vα/Jα recombination in T cells by controlling access of the transcription and recombination machinery to the TCR α loci. The JE131 cell line should prove to be a very useful tool for studying the molecular details of this and other processes involved in the pre-T cell to αßTCR(+) CD4(+) CD8(+) thymocyte transition.

Long non-coding RNA C5orf66-AS1 is downregulated in pituitary null cell adenomas and is associated with their invasiveness.

Pituitary null cell adenoma is a challenging clinical condition, and its pathogenesis remains to be elucidated. We performed this study to determine the roles of C5orf66-AS1, NORAD, and TINCR in the pathogenesis and invasion of pituitary null cell adenomas. Expression of the three long non-coding RNAs in pituitary null cell adenoma tissues of 11 patients and normal pituitary tissues from four donors was examined by performing quantitative reverse transcription-polymerase chain reaction. We found that C5orf66-AS1 expression was lower in pituitary null cell adenoma tissues than in normal pituitary tissues. Moreover, C5orf66-AS1 expression level was significantly lower in invasive pituitary null cell adenomas than in non-invasive ones. After transfection of C5orf66-AS1 into pituitary adenoma cells, assessment of cell viability and invasion suggested that overexpressed C5orf66-AS1 inhibited cell viability and cell invasion. In silico algorithms predicted several cis- and trans-acting target genes of C5orf66-AS1, including PITX1 and SCGB3A1. In addition, expression of some of the predicted target genes was determined using microarray data of another cohort with pituitary null cell adenomas. It showed that some of these target genes were differentially expressed between pituitary null cell adenoma tissues and normal pituitary tissues as well as between invasive and non-invasive tumors. Co-expression analysis in RNA sequencing data showed that PAQR7 was the most correlated gene of C5orf66-AS1 and that several predicted trans-acting target genes, including SCGB3A1, were highly correlated with C5orf66-AS1. NORAD and TINCR expression was not statistically significant in the complete cohort; however, a negative correlation was observed between NORAD expression and maximum tumor diameter in some subgroups. These results indicate that C5orf66-AS1 suppresses the development and invasion of pituitary null cell adenomas. However, our results do not provide enough statistical evidence to support the roles of NORAD and TINCR in the development and invasion of pituitary null cell adenomas.

Subclinical adenomas in postmortem pituitaries: classification and correlations to clinical data.

OBJECTIVE: The aim of this study was to examine pituitary adenomas in a series of postmortem pituitaries by use of modern technologies of immunostaining, to classify the adenomas according to the current WHO classification and to analyse the possible associations to the available clinical data. METHODS: In this study, pituitaries of 3048 autopsy cases obtained from autopsy series of the years 1991-2004 were examined. RESULTS: A total of 334 pituitary adenomas were found in 316 pituitaries. One hundred and thirty-two sparsely granulated prolactin cell adenomas (39.5%), 75 null cell adenomas (22.5%) and 31 oncocytomas were diagnosed. Forty-six ACTH cell adenomas (13.8%, 27 densely granulated, 19 sparsely granulated) and one adenoma composed of Crooke's cells were detected. Twenty-two gonadotroph cell adenomas (6.6%), seven GH cell adenomas (four sparsely granulated, three densely granulated), one mixed GH cell-PRL cell adenoma, two TSH cell adenomas, five plurihormonal adenoma type I, four plurihormonal adenoma type II and two alpha-subunit-only adenomas were seen. Six adenomas remained unclassified because the tissue was not contained in all sections for immunohistochemistry. Seventeen pituitaries included multiple tumours. The overall tumour size ranged from 0.1 to 20 mm in diameter. Among 76 adenomas (22.7%), which had a tumour size of > or = 3 mm, only three tumours were macroadenomas corresponding to a tumour size of more than 10 mm. The evaluation of the available clinical data showed 99 cases of hypertension, 65 cases of diabetes mellitus, six patients with hyperthyroidism and four with hypothyroidism. No symptoms of adenohypophyseal hormone hypersecretion were reported. The statistical correlations to clinical data were discussed. CONCLUSIONS: Adenomas in postmortem pituitaries differ from those in surgical series in proportion of adenoma types and biological behaviour.

Proliferation of infected lymphoid precursors before Moloney murine leukemia virus-induced T-cell lymphoma.

NFS/N mice inoculated with Moloney murine leukemia virus (M-MuLV) developed T-cell lymphoma after a 10-week latent period. Expression of lymphoid differentiation antigens, appearance of M-MuLV-encoded cell surface antigens, and rates of cellular proliferation were measured in splenic and bone marrow subpopulations during this latent period. At 2 weeks of age, Thy-1-and surface immunoglobulin-negative null cells of spleen and bone marrow expressed M-MuLV antigens whereas T- and B-lymphocytes did not. During the 3d and 4th weeks, the number of splenic null cells increased to six times the number found in uninfected controls. These null cells included the precursors of lymphocytes and hematopoietic cells. For the remainder of the latent period, the percentage of null cells undergoing proliferation was three times greater in the infected mice, while the total number of null cells remained constant. This proliferation was not accompanied by terminal differentiation or emigration of mature cell types from the spleen. Proliferation was substantially delayed in CBA mice, which are resistant to lymphoma induction.

Generation of phenotypic diversity in the B16 mouse melanoma relative to spontaneous metastasis.

Serial s.c. transplantation of the B16 melanoma in syngeneic mice for nearly 30 monthly generations effected gradual changes in the incidence of spontaneous pulmonary metastasis. Cell lines derived from s.c. tumors and from secondary tumor growths in the lungs were comparably variable in metastatic predilection and also differed in ability to produce tumor colonies in the lungs following i.v. injection of cultured cells. Some lines metastasized to the lungs from s.c. tumors and also colonized the lungs; others were metastatic but noncolonizing, colonizing and nonmetastatic, or nonmetastatic and noncolonizing ("null"). Metastatic and colonizing activities of all cell lines except the most potent colonizers were unstable in culture and during s.c. growth. Over 150 clones and subclones were obtained from B16 melanoma cell lines, and four distinct categories were defined on the basis of dissemination-related phenotypic characteristics: slow-growing null (Ns); rapid-growing null; metastatic; and colonizing. No single cell belonged to more than one category at the same time, but interconversions occurred rapidly and consistently during growth in vitro and in vivo. Progenitor Ns cells generated metastatic cells in culture and in tumors and became rapid-growing null cells and colonizers solely within tumors. Metastatic activity was transient, with cells reverting back to an Ns phenotype in culture and s.c. or converting to rapid-growing null cells and colonizers in vivo. Only potent colonizers were stable, an apparent end result of phenotypic diversification, but formation or proliferation of these cells within tumors was somehow regulated. Comparable heterogeneity was generated within lung metastases, except that reversion of metastatic cells to Ns cells and regeneration of metastatic activity were not demonstrated; the result was a progressive loss of metastatic cells within developing metastases.

Null cell adenomas of the pituitary gland: an institutional review of their clinical imaging and behavioral characteristics.

The aim of the study was to establish if the null cell adenoma (NCA) forms a distinct subgroup with unique clinicopathological characteristics within the nonfunctioning pituitary adenoma group particularly in relation to the silent gonadotroph adenomas (SGAs). We identified 31 patients with the pathological diagnosis of NCA verified by routine histology and immunohistochemistry with distinct differentiation from SGAs by an established negative testing for SF-1 at the Toronto Western Hospital between December 2004 and August 2010. We reviewed their demographic data, clinical features, magnetic resonance imaging, and the histologic variables: MIB-1, FGFR4, and P27. We compared these to 63 SGAs identified within the same period. All the NCAs were macroadenomas with diameter ranging from 15-57 mm and tumor volumes between 1.95-53.5 mm(3). Preoperative cavernous sinus tumor growth was able to predict the presence of a residual after surgery (p = 0.023). Furthermore, preoperative cavernous sinus extension (p = 0.002) and negative P27 expression (p = 0.035) were able to independently predict the subsequent growth of the postoperative tumor residual. Comparing the NCA to SGA, we found that MIB-1 was higher in NCA (mean ± SD = 3.43 ± 2.76 %) compared to SGAs (mean ± SD = 2.49 ± 1.41 %) (p = 0.044). The preoperative and postoperative tumor volume doubling times (TVDTs) displayed a negative correlation in the SGA (r = -0.855, p = 0.002) while in the NCA, a positive correlation was evident (r = 0.718, p = 0.029). Our study suggests that the NCAs are a distinct group with differing behavioral characteristics from the SGAs. It also appears that the finding of cavernous sinus extension on preoperative imaging and a negative P27 expression on immunohistochemistry in NCAs may be valuable tools in predicting residual tumor growth which may impact on postoperative care.

Terminal lymphoblastic transformation in polycythemia vera.

A patient with polycythemia vera and lymphoblastic transformation is discussed. Phenotypic characterization revealed that the predominant leukemic cells were classic "null" lymphoid cells with a minority component of pre-B cells. This case provides evidence that the stem cell disorder in polycythemia vera may involve the lymphocyte early in development.

The molecular basis for the differential sensitivity of B and T lymphocytes to growth inhibition by thymidine and 5-fluorouracil.

Cultured leukemic lymphocytes originating from patients with T, B and non-T, non-B (null) leukemia were tested for their sensitivity to thymidine and 5-fluorouracil. T cells were found to be 5-7 fold more sensitive to thymidine growth inhibition than B-cells. At 10(-3) M concentration of thymidine, T cells showed a progressive (up to 75%) decline in the populating trypan blue-excluding cells, after 72 h. At this concentration of thymidine B cells showed slight inhibition at 24 and 48 h, then at 72 h the surviving cell level returned almost to the level of unperturbed cells. Thymidine at 10(-5) M concentration, caused 40% cell growth inhibition of T cells, however, at this concentration it had little or no effect on B cells. 5-fluorouracil effects on B and T lymphocytes are opposite to that of thymidine. B cells were on an average 5-7 times more sensitive to 5-FU than T cells. 5-FU at 10(-6) M caused up to 45% inhibition of B-cell growth but at this concentration it had no effect on the growth of T cells. B-, T- and null-lymphocytes sensitivity to thymidine and 5-FU was correlated with the level of the catabolic enzyme thymidine phosphorylase. B cells had, on average, 5-fold more thymidine phosphorylase than T or null cells. Furthermore, the enzyme from the B-cell line (HR1K) chromatographed differently on DEAE-Sephadex than the normal peripheral blood lymphocytes enzyme. The normal enzyme from peripheral blood lymphocytes when adsorbed to DEAE-Sephadex was eluted at a salt concentration of 0.3 M KCI, Enzyme activities of HR1K did not adsorb to the DEAE-Sephadex column but were adsorbed to a phosphocellulose column. Enzyme from normal and leukemic lymphocytes showed similar molecular weights of 130,000 dalton as determined by gel filtration.

Neutrophil-rich Ki-1-positive anaplastic large cell lymphoma: a study by fine-needle aspiration biopsy.

Fine-needle aspiration biopsy (FNAB) is an accurate, cost-effective method of evaluating lymphomas. The neutrophil-rich variant of anaplastic large cell lymphoma (NR-ALCL) is a rare non-Hodgkin lymphoma. To our knowledge, we present thefirst study of NR-ALCL by FNAB cytology. Histologic confirmation was available for both patients. Both cases were positive for Ki-1 (CD-30) and were either T-cell or null-cell phenotype. FNAB specimens were highly cellular with a single-cell pattern composed of pleomorphic tumor cells, "hallmark" tumor cells, and a background rich in neutrophils that occasionally obscured tumor cells. Diagnosis on FNAB is difficult owing to the rarity of this tumor, its resemblance to Hodgkin lymphoma and other non-Hodgkin lymphomas that express CD30, its similarity to an infectious process, and its occasional confusion with metastatic carcinoma and melanoma. Reproducible cytologic features usually are present, and the diagnosis can be made conclusively by FNAB in conjunction with ancillary studies.

Changes in subpopulations of lymphocytes in peripheral blood, and supramammary and prescapular lymph nodes of cows with mastitis and normal cows.

Direct immunofluorescence (IF) and indirect IF techniques were employed to analyze the distribution of B and T lymphocyte populations in peripheral blood, and in supramammary (draining), and prescapular (non-draining) lymph nodes of cows with mastitis and normal cows. In the peripheral blood there was a significant decrease in the percent and absolute number of B lymphocytes in mastitic cows (n = 29; 17.1 +/- 10.2%; 3.4 +/- 2.7 X 10(5) cells/ml) as compared to normal cows (n = 38; 25.2 +/- 7.8%; 9.3 +/- 5.4 X 10(5) cells/ml). The percent T lymphocyte count in mastitic cows (71.2 +/- 7.1%) was slightly increased over that of normals (65.8 +/- 7.2%), although the absolute number of T lymphocytes was decreased in mastitic cows (1.49 +/- 0.91 X 10(6) cells/ml vs. 2.47 +/- 1.28 X 10(6) cells/ml). In the prescapular lymph node the percent of B lymphocytes, but not T or "null lymphocytes", decreased significantly in mastitic cows as compared to that of normals. The decrease, i.e. 32%, paralleled the 32.1% decrease found in peripheral blood B lymphocytes. In contrast, in the supramammary lymph node of mastitic cows, the percent B lymphocytes increased over that of normals (35.1 +/- 2.0% vs. 20.4 +/- 9.4%), whereas the percent T lymphocytes decreased to 54.5 +/- 2.8% compared to 70.7 +/- 3.5% in normal cows. There was no significant change in percent "null lymphocytes". The weight of prescapular lymph nodes did not change in mastitic cows when compared to that of normals. As a result, the estimated number of B lymphocytes, but not of T and "null lymphocytes", decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Pituitary tumors in the elderly.

The present study was designed to investigate the incidence and immunohistochemical characteristics of pituitary tumors in the elderly. In our surgical collection of 1925 cases, we examined tumor tissue from 15 patients over 80 years of age. Pituitaries obtained at routine autopsies from 692 subjects over 80 years of age were also investigated. Of the 15 surgical cases studied, the majority of patients presented with chiasmatic syndromes, likely caused by macroadenomas. Gonadotroph adenomas were the most frequently diagnosed tumor type, followed by null-cell adenomas and oncocytomas. There is only one case with GH cell adenoma. Among 692 autopsy cases, 79 (11.4%) pituitaries were found to contain adenomas in the anterior lobe. In one pituitary, two separate adenomas were detected, hence the number of adenomas in our material was 80. All autopsy cases were microadenomas except one. The mean diameter of adenomas was 2.2 mm. ACTH cell adenomas were the most frequently diagnosed tumor type, followed by PRL cell adenomas and null cell adenomas. The occurrence of pituitary adenomas discovered after routine autopsy in the elderly was common, although these tumors were not found frequently in surgical cases over 80 years of age. Our immunohistochemical study revealed that many tumors contained one or more than one anterior pituitary hormone, although almost all pituitary adenomas were considered to be clinically inactive in surgical and autopsy cases.

[Null-cell non-Hodgkin's lymphoma presenting with a mass in the chest wall after tuberculous pyothorax].

A 59-year-old male, who was treated with artificial pneumothorax for pulmonary tuberculosis 42 years previously, presented with a painful mass in the left lateral chest wall and lymph node swelling in the left neck. A chest CT-scan revealed a tumor shadow extending from the outer chest wall to the pleural cavity containing pus surrounded by calcified pleura. 67Ga scintigraphy showed accumulation of the radionuclide in the left lateral chest and left neck. Biopsy specimen obtained from both the chest tumor and cervical lymph node revealed diffuse large cell lymphoma. Immunostaining failed to demonstrate CD1, CD3, CD4, CD8, CD13, CD20, immunoglobulin, alpha, gamma, mu, delta, kappa and lambda chains, indicating null cell characteristics. Chemotherapy consisting of cyclophosphamide, doxorubicin, vincristine, prednisolone and bleomycin and irradiation resulted in a temporary decrease of the tumor and lymph nodes, but the patient died of pneumonia 14 months after the onset of disease. Since the levels of serum lactate dehydrogenase and immunosuppressive acidic protein varied in parallel to the disease activity, they appeared to be useful for the assessment of therapeutic effects during the clinical course. Approximately 100 cases of non-Hodgkin's lymphoma developing after tuberculous pyothorax have been reported in this country, among which the incidence of null cell type is exceedingly rare.

Correlation between histological subtypes and MRI findings in clinically nonfunctioning pituitary adenomas.

Clinically nonfunctioning pituitary adenomas (CNFPAs) consist of several histological subtypes, including null cell adenoma (NCA), silent gonadotroph cell adenoma (SGA), silent corticotroph adenoma (SCA), and other silent adenomas (OSA) (i.e., GH, TSH, and prolactin adenomas). To detect possible correlations between MRI findings and the subtypes, we retrospectively studied 390 consecutive patients with CNFPA who underwent surgery between 2008 and 2010. They were classified into three groups: NCA/SGA (313 cases), SCA (39 cases), and OSA (36 cases); in addition there were two unusual cases of plurihormonal adenoma. Three MRI findings were less common in NCA/SGA than in the other groups (P < 0.0001): giant adenoma (>40 mm), marked cavernous sinus invasion (Knosp grade 4), and lobulated configuration of the suprasellar tumor. When these MRI findings were negative in patients older than 40 years old, 91.0% (212/233) were NCA/SGA. These MRI findings were frequently noted despite a low MIB-1 index in SCA. OSA showed a high MIB-1 index and a preponderance in younger patients. In conclusion, although SCA and OSA consisted of only 20% of CNFPAs, their frequency significantly increased when the tumor was large, invasive, and lobulated, and the patient was younger than 40 years old.

Local inflammation is associated with aortic thrombus formation in abdominal aortic aneurysms. Relationship to clinical risk factors.

Intraluminal thrombus formation in aortic abdominal aneurysms (AAA) is associated with adverse clinical prognosis. Interplay between coagulation and inflammation, characterised by leukocyte infiltration and cytokine production, has been implicated in AAA thrombus formation. We studied leukocyte (CD45+) content by flow cytometry in AAA thrombi from 27 patients undergoing surgical repair. Luminal parts of thrombi were leukocyte-rich, while abluminal segments showed low leukocyte content. CD66b+ granulocytes were the most prevalent, but their content was similar to blood. Monocytes (CD14+) and T cells (CD3+) were also abundant, while content of B lymphocytes (CD19+) and NK cells (CD56+CD16+) were low. Thrombi showed comparable content of CD14highCD16- monocytes and lower CD14highCD16+ and CD14dimCD16+, than blood. Monocytes were activated with high CD11b, CD11c and HLA-DR expression. Total T cell content was decreased in AAA thrombus compared to peripheral blood but CD8 and CD3+CD4-CD8- (double negative T cell) contents were increased in thrombi. CD4+ cells were lower but highly activated (high CD69, CD25 and HLA-DR). No differences in T regulatory (CD4+CD25+FoxP3+) cell or pro-atherogenic CD4+CD28null lymphocyte content were observed between thrombi and blood. Thrombus T cells expressed high levels of CCR5 receptor for chemokine RANTES, commonly released from activated platelets. Leukocyte or T cell content in thrombi was not correlated with aneurysm size. However, CD3+ content was significantly associated with smoking in multivariate analysis taking into account major risk factors for atherosclerosis. In conclusion, intraluminal AAA thrombi are highly inflamed, predominantly with granulocytes, CD14highCD16- monocytes and activated T lymphocytes. Smoking is associated with T cell infiltration in AAA intraluminal thrombi.