Clonal analysis of solitary follicular nodules in the thyroid.

Accumulated data using functional, morphologic, and histochemical analysis suggests that follicular proliferations in the thyroid include polyclonal and monoclonal patterns with encapsulated follicular adenomas most frequently monoclonal, and other nodules generally polyclonal. However, examples of polyclonal carcinomas or adenomas raise the possibility that histologically similar lesions may arise through different pathogenetic mechanisms. The authors have performed a clonal analysis of histologically benign and malignant thyroid nodules in seven women using HPRT (hypoxanthine phosphoribosyl transferase) and PGK (phosphoglycerate kinase) restriction fragment length polymorphisms (RFLPs) on the X chromosome. These RFLPs used in concert with methylation-sensitive restriction endonucleases HpaII and HhaI permit distinction of active and inactive X chromosomes. DNA from a multinodular goiter showed equal sensitivity of both X chromosome RFLP alleles to a methylation-sensitive restriction endonuclease, consistent with a polyclonal origin. In contrast, three solitary follicular nodules and three carcinomas displayed predominant sensitivity of a single RFLP allele, consistent with a monoclonal origin. Although further detailed studies will be necessary to understand polyclonal origins reported for some adenomas, our data from a limited number of samples supports a predominantly monoclonal origin, and possible neoplastic pathogenesis, for many solitary adenomatous nodules in the thyroid.     

Immunopathology of follicular lymphomas. A model of B-lymphocyte homing.

To investigate whether follicular lymphoma has a monoclonal origin, we stained frozen tissue sections from 22 afflicted patients for kappa and lambda light chains with an immunofluorescence technic. F(ab')2 antibody fragments were used to avoid binding by Fc receptors. In 20 cases the lymphoma nodules comprised a monoclonal population of immunoglobulin-producing cells. The nodules were usually surrounded by a normal, polyclonal population of B lymphocytes. Reactive lymphoid follicles were easily differentiated from lymphoma nodules on the basis of clonality. Eight cases contained multiple immunoglobulin heavy chains. All the lymphoma nodules in the same tissue or in multiple tissues in the same patient showed identical light-chain and heavy-chain staining even if different histologic subtypes were identified. Follicular lymphoma is the outgrowth of a single clone of immunoglobulin-bearing cells that retain the tissue-homing characteristics of B lymphocytes.     

Lung Carcinoma Metastatic to Microfollicular Adenoma of the Thyroid A Case Report

A 75-year-old woman with lung adenocarcinoma in whom autopsy revealed metastasis to microfollicular adenoma of the thyroid is described. A thyroid tumor specimen from this patient was initially interpreted as representing primary encapsulated follicular carcinoma of the thyroid associated with a component of poorly differentiated carcinoma of follicular cell origin. The widespread involvement of the lungs and other sites was also interpreted as metastases from the poorly differentiated carcinoma component within the encapsulated follicular carcinoma of the thyroid. Subsequent meticulous histologic examination revealed that the thyroid tumor was a microfollicular adenoma, and that the component of poorly differentiated carcinoma within it was the same as the lung carcinoma. Immunohistochemical investigation revealed that the poorly differentiated carcinoma cells within the thyroid tumor were stained positively with polyclonal and monoclonal antibodies against carcinoembryonic antigen (CEA) and negative for thyroglobulin and calcitonin. The carcinoma cells from the lungs and other sites also showed positive staining for CEA. These findings support the view that the component of poorly differentiated carcinoma was a metastatic lesion from the primary lung carcinoma to the microfollicular adenoma of the thyroid. The present study emphasizes that attention should be directed to thyroid metastasis, even if it is within a thyroid primary neoplasm.     

Lung carcinoma metastatic to microfollicular adenoma of the thyroid. A case report

A 75-year-old woman with lung adenocarcinoma in whom autopsy revealed metastasis to microfollicular adenoma of the thyroid is described. A thyroid tumor specimen from this patient was initially interpreted as representing primary encapsulated follicular carcinoma of the thyroid associated with a component of poorly differentiated carcinoma of follicular cell origin. The widespread involvement of the lungs and other sites was also interpreted as metastases from the poorly differentiated carcinoma component within the encapsulated follicular carcinoma of the thyroid. Subsequent meticulous histologic examination revealed that the thyroid tumor was a microfollicular adenoma, and that the component of poorly differentiated carcinoma within it was the same as the lung carcinoma. Immunohistochemical investigation revealed that the poorly differentiated carcinoma cells within the thyroid tumor were stained positively with polyclonal and monoclonal antibodies against carcinoembryonic antigen (CEA) and negative for thyroglobulin and calcitonin. The carcinoma cells from the lungs and other sites also showed positive staining for CEA. These findings support the view that the component of poorly differentiated carcinoma was a metastatic lesion from the primary lung carcinoma to the microfollicular adenoma of the thyroid. The present study emphasizes that attention should be directed to thyroid metastasis, even if it is within a thyroid primary neoplasm.     

Adenomatoid nodules are the main cause for discrepant histology in 234 thyroid fine-needle aspirates reported as follicular neoplasm

According to several large studies, the surgical pathologist renders a non-neoplastic diagnosis in ～20-40% of thyroid fine-needle aspiration (FNA) cases reported as follicular neoplasm. This study analyzes the cause of this poor correlation between cytology and histology. Cases consisting of oncocytic (Hurthle) cells were excluded from study. During the study period from January 1996 to April 2010, histologic follow-up was available for 234 of 670 cases (34.9%) reported as follicular neoplasm on ultrasound-guided thyroid FNA. Sonographic and Doppler data were available in all cases and included nodule location, size, echogenicity, and vascularity. Of the 234 aspirates with follow-up, surgical pathology reported 130 cases (55.6%) of follicular adenoma, 15 cases (6.4%) of follicular carcinoma, 14 cases (6.1%) of follicular variant of papillary carcinoma, and 75 cases (32.3%) of nodular goiter. Recuts of those index nodules reported as nodular goiter were examined independently by two pathologists using the 2× objective lens. Adenomatoid nodule was defined as an insufficiently encapsulated "blue" nodule of increased nuclear density when compared with the surrounding thyroid. Of the 75 cases reported as nodular goiter, 60 index nodules (80%) fulfilled the described criteria for adenomatoid nodule, while 15 did not. In conclusion, adenomatoid nodules are the main cause of poor histologic correlation with follicular neoplasm reported by FNA. If "increased nuclear density at scanning magnification" were adopted by surgical pathologists as the major diagnostic criterion for follicular adenoma rather than encapsulation, noncorrelated cases would be reduced from 32 to 6.4%.     

“Cellular adenomatoid nodules” of the thyroid: Review of 219 fine-needle aspirates

We reviewed 219 consecutive thyroid aspirates previously diagnosed as “cellular adenomatoid nodule.” applying the criteria presented in this paper and reclassifying them as 146 adenomatoid nodules (AN), 31 cellular adenomatoid nodules (CELL-AN), 29 cellular adenomatoid nodules vs. follicular neoplasms (CELL-AN vs. FN), 5 follicular neoplasms (FN), 2 FN of oxyphilic cell type, 4 papillary carcinomas, and 2 chronic lymphocytic (Hashimoto's) thyroiditis. Of the 146 adenomatoid nodules, 14 occurred in multinodular goiters on histologic examination. Of the 31 CELL-AN, five had surgery: two were follicular adenomas, one was papillary carcinoma, and two were multinodular goiters. Of the 29 CELL-AN vs. FN, 11 had surgery: six were follicular adenomas, two were follicular carcinomas, two were multinodular goiters, and one was Hashimoto's thyroiditis. Surgery on four FN showed follicular adenomas (a fifth patient was lost to follow-up). Of the two FN of oxyphilic cell type, one was a multinodular goiter and the other a follicular adenoma with oxyphilic cells. Three of the four papillary carcinomas were confirmed histologically (one patient was lost to follow-up). Of the two cases showing Hashimoto's thyroiditis, one was diagnosed as FN on repeat aspiration and follicular carcinoma at surgery. After review, we identified 40 patients at higher risk of harboring a neoplasm and 31 with cellular adenomatoid nodules. Twenty-five underwent surgery with the above results. In the classification of follicular lesions of the thyroid by FNA, adherence to strict cytologic criteria helps identify those patients who will benefit most from surgery.     

The clonal origin of thyroid nodules and adenomas.

The clonal origin of thyroid tumors in female mice heterozygous for a deficiency of the X-linked enzyme glucose-6-phosphate dehydrogenase (G6PD) was studied. Tumor phenotype was demonstrated by enzyme histochemistry. Because monophenotypia is not synonymous with monoclonality, a method to estimate the degree of mingling of the two cellular phenotypes in normal tissue was devised. Twenty-five point three percent of 624 randomly chosen pairs of adjacent follicular cells were of unlike phenotype, suggesting that if tumors were derived from 2 or more cells at least a quarter would express polyphenotypia. Four hundred fifty-three thyroid lesions induced in 20 GPDX (enzyme-deficient) mice, 20 C3H (normal) mice, and 48 heterozygous (C3HxGPDX) mice by radiation and long-term goitrogen treatment were studied. One hundred twenty-eight adenomas (sharply defined or encapsulated hypercellular lesions) were found in heterozygotes; 108 (84%) were monophenotypic, and 20 (16%) were largely monophenotypic with degenerate areas or included normal cells. None were clearly polyphenotypic. Seventy-five nodules (circumscribed but not encapsulated, largely normocellular lesion with prominent stroma) were found in heterozygotes; 25 (33%) only were monophenotypic. It is concluded that thyroid adenomas are monoclonal and nodules polyclonal. The variegated pattern of polyphenotypia in the nodules together with their prominent stromal component leads to the suggestion that there is a causative role for the stroma in their generation.     

High molecular weight caldesmon positive stromal cells in the capsule of thyroid follicular tumours and tumour-like lesions

AIMS: To investigate the smooth muscle nature of the spindle stromal cells in the capsule of thyroid tumours and tumour-like lesions. METHODS: Immunostaining for high molecular weight caldesmon (HCD), a highly specific marker for smooth muscle differentiation, was performed in 70 primary thyroid tumours and tumour-like lesions (21 hyperplastic nodules, 29 follicular adenomas, five minimally invasive follicular carcinomas, six widely invasive follicular carcinomas, and nine encapsulated papillary carcinomas). RESULTS: HCD positive stromal cells (HCD+ cells) were detected in the capsule of 20 of the 21 hyperplastic nodules, and all of the 29 follicular adenomas and five minimally invasive follicular carcinomas, whereas HCD+ cells were seen in the capsule of only four of the six widely invasive follicular carcinomas and no HCD+ cells were seen in the capsule of the nine encapsulated papillary carcinomas examined. CONCLUSIONS: The presence of HCD+ cells in the capsule is characteristic of thyroid follicular tumours and tumour-like lesions. The stromal cells in the capsule of thyroid follicular tumours and tumour-like lesions are different from those of encapsulated papillary carcinoma.     

Atypical adenoma of the thyroid. A clinicopathologic and flow cytometric DNA study in comparison with other follicular neoplasms.

A clinicopathologic and DNA flow cytometric study was performed on seven patients (three males, four females) with atypical adenoma of the thyroid gland, using formalin-fixed paraffin-embedded tissues. The results were compared with those of 30 follicular adenomas and 13 follicular carcinomas. The patients ranged in age from 32 to 74 years (mean; 55.8 years), and the mean follow-up period was 11.0 years. All patients except two who died of other diseases were free of thyroid disease after initial surgery. It showed that there was no evidence of clinical cancer in this follow-up study of patients operated on for atypical adenomas. Four of the atypical adenomas were diploid, two were aneuploid, and one was tetraploid. Twenty-seven of the 30 follicular adenomas were diploid. Three patients with aneuploid follicular adenoma were free of disease. Of the 13 follicular carcinomas with a mean follow-up period of 6.9 years, five were diploid, seven were aneuploid, and one was tetraploid. Two patients with aneuploid follicular carcinoma and one with diploid carcinoma developed lung metastases, and one patient each with diploid and aneuploid follicular carcinoma died of disease. There was no significant correlation between histologic features, ploidy status and prognosis among follicular carcinomas. The results of this study suggest that DNA flow cytometric analysis is not a useful tool for predicting the clinical behavior of follicular neoplasms.     

Late bone metastasis from an encapsulated follicular carcinoma of the thyroid withoutcapsular and vascular invasion

A unique case of encapsulated follicular carcinoma of the thyroid, which lacked histologic evidence of capsular and vascular Invasion but developed a late bone metastasis, is described. The thyroid tumor was found in a 42-year-old man. It was relatively small (2.5 cm) and totally encapsulated. Histologically, the thyroid tumor showed a microfollicular growth pattern of follicular cells and revealed no histologic evidence of nuclear atypia, mitotic figures or capsular and vascular invasion. The diagnosis of microfollicular adenoma was made and partial thyroidectomy was performed. Bone (rib) metastasis of the thyroid tumor developed 22 years after the thyroidectomy. The present case suggested that capsular and/or vascular invasion is not always sufficient for the diagnosis of encapsulated follicular carcinoma of the thyroid.     

Clonal analysis of micronodules in virus C-induced liver cirrhosis using laser capture microdissection (LCM) and HUMARA assay

Most hepatocellular carcinomas (HCC) arise from malignant transformation of regenerative cirrhotic nodules. Because HCC has a very poor prognosis, detection of these premalignant lesions may improve the management of patients with cirrhosis. In this regard, clonal analysis of liver micronodules should be of particular interest in order to differentiate polyclonal regenerative micronodules from monoclonal neoplastic potentially malignant micronodules. To address this issue, 112 micronodules from 15 cases of explanted liver cirrhosis were carefully microdissected from paraffin-embedded tissue using a laser capture microscopy system. Clonal analysis was performed by analyzing X-chromosome inactivation, as indicated by the methylation status of the human androgen receptor gene (HUMARA). For each microdissected micronodule, a large set of pathological features was evaluated and correlated with their clonal status. Clonal analysis showed that 57 micronodules (51%) were monoclonal and 55 (49%) were polyclonal. Prevalence of monoclonal nodules ranged from 25% to 71% according to cases. In all cases, mono- and polyclonal nodules were randomly distributed in the cirrhotic liver. Although the clonal status was not significantly affected by the presence or absence of macronodules in the adjacent liver, size of monoclonal micronodules was significantly larger than size of polyclonal micronodules (mean size of the monoclonal nodules: 3 + 0.1 mm vs mean size of the polyclonal nodules: 2.5 +/- 0.1 mm, p = 0.007). Among the elementary pathological features evaluated, only the presence of iron overload was correlated with a monoclonal status (p = 0.04). In conclusion, clonal analysis of liver cirrhosis shows that 51% of micronodules are monoclonal lesions, supporting the notion that liver cirrhosis is a multineoplastic lesion. Because monoclonality is a marker of neoplasia, cirrhosis with accumulation of monoclonal nodules may be carefully followed, and monoclonal nodules should be screened for additional markers to assess their biological behavior.     

Atypical Adenoma of the Thyroid: A Clinicopathologic and Flow Cytometric DNA Study in Comparison with Other Follicular Neoplasms

A clinicopathologic and DNA flow cytometric study was performed on seven patients (three males, four females) with atypical adenoma of the thyroid gland, using formalin-fixed paraffin-embedded tissues. The results were compared with those of 30 follicular adenomas and 13 follicular carcinomas. The patients ranged in age from 32 to 74 years (mean: 55.8 years), and the mean follow-up period was 11.0 years. All patients except two who died of other diseases were free of thyroid disease after initial surgery. It showed that there was no evidence of clinical cancer in this follow-up study of patients operated on for atypical adenomas. Four of the atypical adenomas were diploid, two were aneuploid, and one was tetraploid. Twenty-seven of the 30 follicular adenomas were diploid. Three patients with aneuploid follicular adenoma were free of disease. Of the 13 follicular carcinomas with a mean follow up period of 6.9 years, five were diploid, seven were aneuploid, and one was tetraploid. Two patients with aneuploid follicular carcinoma and one with diploid carcinoma developed lung metastases, and one patient each with diploid and aneuploid follicular carcinoma died of disease. There was no significant correlation between histologic features, ploidy status and prognosis among follicular carcinomas. The results of this study suggest that DNA flow cytometric analysis is not a useful tool for predicting the clinical behavior of follicular neoplasms. Acta Pathol Jpn 42: 632–638, 1992.     

Thyroid pathologic findings in patients with Cowden disease

We describe the histologic findings in thyroid glands from six female and five male patients with Cowden disease. The patients were aged 9 to 43 years (mean age, 26 years). The salient thyroid lesions in this syndrome were multicentric follicular adenomas and adenomatous (parenchymatous, hyperplastic) nodules showing a wide range of nonspecific cytoarchitectural patterns. Multiple tiny cellular foci, so-called microadenomas, were also a feature. Specific lesions composed of oxyphil or clear cells, a tumor with features of hyalinizing trabecular adenoma, and an adenolipoma also occurred. Two cases showed a follicular carcinoma in addition to multiple benign follicular cell proliferations. The follicular carcinomas occurred at an older age and were larger in size than the clinically significant benign nodular lesions, suggesting tumor progression. All tumors showed thyroglobulin immunoreactivity and were negative for calcitonin. The histologic findings of a multiple adenomatous goiter or multiple follicular adenomas, particularly in children and young adults, should alert the pathologist and physician to the possibility of an inherited trait, such as Cowden disease, with its implications for family screening. The tumors are usually benign and well demarcated, but, because of multicentricity and increased risk of recurrence or progression to carcinoma, total thyroidectomy should be advocated.     

Comparison of different polymerase chain reaction-based approaches for clonality assessment of immunoglobulin heavy-chain gene rearrangements in B-cell neoplasia.

Several frequently applied polymerase chain reaction strategies for analysis of immunoglobulin heavy-chain gene rearrangements were compared by analyzing 70 B-cell lymphoproliferative disorders and 24 reactive lymphoid lesions. Southern blot analysis was used as the "gold standard" for clonality assessment. For polymerase chain reaction analysis, primers directed against framework (FR) 3 (FR3-A and FR3-B), FR2, and FR1 of the variable gene segments and against joining gene segments of the immunoglobulin heavy-chain gene were used. Polymerase chain reaction products were analyzed by high-resolution fingerprinting analysis using radiolabeled nucleotides, gene scanning using fluorochrome-labeled primers, and heteroduplex analysis. All of the assays generated polyclonal patterns in the reactive tissues. The sensitivity in detecting monoclonality as defined by Southern blotting varied between 60% (heteroduplex analysis with FR3 primers) and 77% (high-resolution fingerprinting analysis with FR2 primers). Comparison of the three FR3 assays revealed that gene scanning had the highest sensitivity (69%), probably because it could detect small aberrant monoclonal amplicons. False-negative results were especially frequent in follicular center lymphoma (n = 20), but also in diffuse large B-cell lymphoma (n = 18), both renowned for having mutated variable gene segments, potentially leading to primer mismatching. For example, in follicular center lymphoma, the FR3, FR2, and FR1 region primer sets detected clonality in only 35 to 40, 65, and 50%, respectively. Combining these techniques, 17 (85%) of 20 follicular center lymphoma samples showed monoclonality. Therefore, especially in follicular center lymphoma, diffuse large B-cell lymphoma, and, to a lesser extent, in other lymphomas, multiple variable gene segment primer sets must be used for a reliable assessment of clonality. Our results also suggest that gene scanning is somewhat more sensitive than other read-out systems. Heteroduplex analysis, however, is a reliable alternative within a diagnostic setting, avoiding the use of radioactivity or expensive automated sequencing equipment and fluorochrome-labeled (oligo)nucleotides.     

Thyroid nodules with FNA cytology suspicious for follicular variant of papillary thyroid carcinoma: follow-up and management

Thyroid nodules diagnosed as follicular neoplasm on fine-needle aspiration biopsy (FNAB) may represent hyperplastic/adenomatous nodules, follicular adenoma or carcinoma, and follicular variants of papillary thyroid carcinoma (FVPTC) on histologic follow-up. In our laboratory, we attempted to identify a subset of cases which showed cellular specimens with focal features (nuclear chromatin clearing, membrane thickening, and rare grooves) suspicious for the follicular variant of papillary thyroid carcinoma. These cases are reported as follicular-derived neoplasms with nuclear features suspicious for FVPTC to distinguish them from those diagnosed as follicular neoplasm. This study documents our experience with 52 cases so diagnosed and followed prospectively with histologic follow-up. A neoplastic nodule was confirmed in 45/52 cases (86%), of which 40 were malignant (77%). FVPTC was identified in 35/52 cases (67%). Four cases were usual papillary carcinoma, 3 were follicular adenoma, 2 were Hürthle-cell adenoma, and 1 was insular carcinoma. In 7 cases, the subsequent histologic findings were nonneoplastic (5 hyperplastic nodules and 2 colloid nodules). Our prospective study shows that in cellular smears from thyroid nodules, a careful search for the nuclear features of papillary carcinoma should be performed, and it is appropriate to diagnose cases as suspicious for FVPTC if the nuclear features of papillary carcinoma are focal. The surgical management of this group may include an intraoperative confirmation of cytologic diagnosis by scrape preparation and/or frozen section in order to avoid a second surgical intervention for completion thyroidectomy.     

Comparison between echo-color Doppler sonography features and angioarchitecture of thyroid nodules

This study compared echo-color Doppler sonography features of thyroid nodules with the 3-dimensional reconstruction to find parameters useful for the preoperative diagnosis. Forty nodules relative to 29 patients were examined with echo-color Doppler before surgery. After histologic diagnosis, blocks were deparaffinized and prepared for 3-dimensional examination using a stereomicroscope. Echo-color Doppler type I nodules (8 nodules) always corresponded to colloid goiter. Type II and III nodules corresponded to colloid goiter with intralesional hemorrhage or were associated with hyperplastic nodules, follicular adenoma, follicular carcinoma minimally invasive, papillary carcinoma, and medullary carcinoma. Of interest was that 9 of 11 follicular lesions were characterized by a large central vessel, which was also evident in echo-color Doppler images. This architectural pattern is not seen in benign nodules or in papillary carcinomas. Comparison with histology suggests that echo-color Doppler images can visualize vessels showing a muscular wall.     

The ultimobranchial gland and congenital thyroid abnormalities in man

This study was carried out to investigate the fate of the ultimobranchial contribution to the thyroid in man when the thyroid lobe is not fully descended. Thyroid abnormalities were recorded in 41 of 29,000 autopsies at the London Hospital--a prevalence of 1.41/1000. The 18 major abnormalities included four cases of lingual thyroid, in two of which cystic structures were noted in the neck in the region of the upper parathyroid. Three further cases of lingual thyroid with upper parathyroid cysts were collected from other sources. The multilobulated cystic structures were up to 1.5 cm in diameter and showed a variety of histologic features. In four cases there were glandular nodules of up to 1 mm across lying in the intercystic connective tissue. These nodules showed solid areas of irregularly distributed cells that stained positively for calcitonin and calcitonin gene-related peptide, intermingled with, and sometimes apposed to, follicular structures that showed follicular cells and colloid that stained for thyroglobulin. This study has provided conclusive evidence that the ultimobranchial body contributes both C cells and follicular cells to the thyroid in man, has documented the prevalence of congenital defects of thyroid development, and has described the human ultimobranchial gland as showing a wide developmental potential which may have implications in the histogenesis of thyroid neoplasia.     

Muscular cushions of the vessel wall at the periphery of thyroid nodules.

Insufficient vascular compliance might be the cause of regressive changes commonly observed within long-standing thyroid nodules. This hypothesis induced us to study the morphology of vessels at the periphery of nodular thyroid lesions. A series of 104 consecutive nodular goiters and 10 follicular adenomas were collected and stained for elastic fibers and alpha smooth muscle actin to study the morphology of vessel walls. Ninety carcinomas of different histologic type were reviewed as well. Cases of diffuse thyroid enlargement, such as Grave's disease and Hashimoto's thyroiditis, served as controls. In the peripheral zone of eight follicular adenomas and of about 50% of nodular goiters, muscular cushions, connected with the vessel walls, were merged within the fibrous tissue. Such structures were found only in five out of 90 cases (6%) of carcinomas and only when the tumors developed in a gland affected by long-standing nodular goiter. Muscular cushions were never observed in cases of diffuse thyroid enlargement. Such cushions were stained with anti-smooth muscle actin antibody and showed variable amount of elastic fibers, suggesting an origin either from arterial or vein walls. We suggest that the muscular cushions of the vessel walls are the result of nodular thyroid disease and that they should be considered real anatomical entities with a specific function as sphincteric structures.     

Evidence of clonality in chronic neutrophilic leukaemia

BACKGROUND: Chronic neutrophilic leukaemia (CNL) is a rare myeloproliferative disorder of elderly patients characterised by sustained neutrophilia and splenomegaly. The diagnosis of CNL requires the exclusion of BCR/ABL positive chronic myelogenous leukaemia (CML) and of leukaemoid reactions (LRs). The differentiation between CNL and LR is problematic because both conditions share similar morphological features; it is also important because patients with CNL generally have a poor prognosis. AIMS: To determine whether CNL and LR could be distinguished on the basis of different clonality patterns. METHODS: Blood samples from 52 women were studied using the human androgen receptor gene assay (HUMARA). RESULTS: Monoclonality was found in the neutrophils in all 17 patients with different myeloproliferative syndromes (MPSs), including those with CNL. In four of the patients with CNL, autologous T cells were also monoclonal, suggesting that they belonged to the neoplastic clone. This finding was in contrast to other MPSs in which T cells were almost always polyclonal. Of nine patients with clinically suspected LR, the neutrophils of five were polyclonal, whereas three patients had monoclonal neutrophils, suggesting that they might be in the process of developing an MPS. Among 26 healthy blood donors, 20 had polyclonal neutrophils and five showed skewed clonality patterns. One case of LR and one normal blood donor were scored "not informative" at the HUMARA locus. CONCLUSIONS: Clonality studies of blood neutrophils using HUMARA aid in distinguishing female patients with monoclonal CNL from those with LR. For the diagnosis of CNL, monoclonality of the neutrophils should be demonstrated whenever possible.