Head Lymph Nodes Research Articles

Computed tomographic appearance of masticatory myositis in dogs: 7 cases (1999–2006)

To document computed tomography (CT) features in dogs with masticatory myositis. Retrospective case series. 7 dogs with an immunologic diagnosis of masticatory myositis and an absence of clinical abnormalities of any skeletal muscles other than the masticatory muscles. History; clinical, hematologic, biochemical, immunologic, cytologic, and histologic findings; and pre- and postcontrast CT imaging features of masticatory muscles and head and neck lymph nodes were extracted from medical records. On CT images, changes in size (atrophy or swelling) were common for all masticatory muscles except the digastricus muscles, which were involved only in 1 dog. Pre-contrast attenuation changes, most often hypoattenuation with varied distribution patterns, were seen in masticatory muscles of 4 dogs. Contrast enhancement with a predominantly inhomogeneous distribution pattern was seen in the temporalis, masseter, and pterygoid muscles of all dogs. Head and neck lymph nodes were enlarged in all but 1 dog and had contrast enhancement with predominantly central or homogeneous distribution patterns. Muscle biopsy was performed in 6 dogs, with biopsy specimens obtained from areas that had the most obvious contrast enhancement on CT images. For all 6 dogs, biopsy specimens had histologic features indicative of masticatory myositis. Results suggested that CT may be a useful adjunct in the diagnosis of masticatory myositis in dogs, including selection of sites for diagnostic muscle biopsy.

Pathology and FDG PET Correlation of Residual Lymph Nodes in Head and Neck Cancer After Radiation Treatment

This study determines if postradiotherapy [18F]fluorodeoxyglucose positron emission tomography (FDG PET) can predict the pathology status of residual cervical lymph nodes in patients undergoing definitive radiotherapy for head and neck squamous cell carcinoma (HNSCC). Patients with stage N2 or higher HNSCC underwent PET and CT imaging after definitive radiotherapy. Patients with radiographically persistent lymphadenopathy underwent either neck dissection or fine needle aspiration (FNA) of the lymph nodes under ultrasound guidance. PET scan results were correlated with the pathologic findings of the residual lymphadenopathy. Twenty-four hemi-necks in 23 patients with residual lymphadenopathy had neck dissection or FNA. The pathology correlated strongly with the post-RT FDG PET studies. All patients with a negative post-RT FDG PET and those with a maximum standardized uptake value (SUVmax) of less than 3.0 in the post-RT FDG PET were found to be free from residual viable tumor. Using a SUVmax of less than 3.0 as the criterion for a negative FDG PET study, the sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 84.2%, 62.5%, and 100%, respectively. A negative post-RT FDG PET is very predictive of negative pathology in the residual lymph node after definitive radiotherapy for advanced HNSCC. A prospective clinical trial is warranted to determine if neck dissection can be withheld in these patients.

Head and Neck Cancer: Dedicated FDG PET/CT Protocol for Detection—Phantom and Initial Clinical Studies

To retrospectively compare the sensitivity of a dedicated fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) protocol versus a standard whole-body PET/CT protocol for detection of head and neck cancer, with biopsy and follow-up as reference standards. Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. Dedicated and standard PET/CT protocols were performed in a phantom and in 55 patients suspected of having head and neck cancer (28 men, 27 women; age range, 21-79 years). The neck phantom contained four 4.4-9.8-mm-diameter spheres. Standard protocol consisted of a midcranium to proximal thigh emission scan of 2-4 minutes per bed position. Dedicated protocol was an 8-minute head and neck scan. Reconstructed field of view and pixel size, respectively, were 30 cm and 2.34 mm for the dedicated and 50 cm and 3.91 mm for the standard protocol. FDG uptake was evaluated visually and semiquantitatively by using standardized uptake values (SUVs). Mean SUV was compared between dedicated and standard protocols with a t test modified for clustered sampling. Receiver operating characteristic (ROC) curves were calculated. A two-tailed P value was used. In the phantom study, a larger percentage difference (20%-27%) in sphere-to-background ratios with the dedicated than with the standard protocol was observed for 6.0-9.8-mm spheres. In the clinical study, a total of 149 lymph nodes were identified. Five malignant and six benign lymph nodes (mean diameter, 7.1 mm) were visually identified with the dedicated protocol only. SUVs with the dedicated protocol were significantly higher than those with the standard protocol (P<.001). Area under the ROC curve was 0.94 for the dedicated and 0.92 for the standard protocol (P=.56). FDG PET with either the standard or dedicated protocol was more sensitive than CT for evaluating head and neck lymph nodes. The dedicated protocol improved the detectability of smaller nodes.

O161 Regional lymph nodes in head and neck squamous cell cancer (H&NSCC) and changes induced by IRX-2 Immunotherapy

O161 Regional lymph nodes in head and neck squamous cell cancer (H&NSCC) and changes induced by IRX-2 Immunotherapy

O49 FLT-PET does not distinguish between metastatic and reactive lymph nodes in head and neck cancer patients

O49 FLT-PET does not distinguish between metastatic and reactive lymph nodes in head and neck cancer patients

18F-FLT PET Does Not Discriminate Between Reactive and Metastatic Lymph Nodes in Primary Head and Neck Cancer Patients

Repopulation of clonogenic tumor cells is inversely correlated with radiation treatment outcome in head and neck squamous cell carcinomas. A functional imaging tool to assess the proliferative activity of tumors could improve patient selection for treatment modifications and could be used for evaluation of early treatment response. The PET tracer 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) can image tumor cell proliferation before and during radiotherapy, and it may provide biologic tumor information useful in radiotherapy planning. In the present study, the value of (18)F-FLT PET in determining the lymph node status in squamous cell carcinoma of the head and neck was assessed, with pathology as the gold standard. Ten patients with newly diagnosed stage II-IV squamous cell carcinoma of the head and neck underwent (18)F-FLT PET before surgical tumor resection with lymph node dissection. Emission (18)F-FLT PET and CT images of the head and neck were recorded and fused, and standardized uptake values (SUVs) were calculated. From all 18 (18)F-FLT PET-positive lymph node levels and from 8 (18)F-FLT PET-negative controls, paraffin-embedded lymph node sections were stained and analyzed for the endogenous proliferation marker Ki-67 and for the preoperatively administered proliferation marker iododeoxyuridine. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated for (18)F-FLT PET. Primary tumor sites were oral cavity (n=7), larynx (n=2), and maxillary sinus (n=1). Nine of the 10 patients examined had (18)F-FLT PET-positive lymph nodes (SUV(mean): median, 1.2; range, 0.8-2.9), but only 3 of these patients had histologically proven metastases. All metastatic lymph nodes showed Ki-67 and iododeoxyuridine staining in tumor cells. In the remaining 7 patients, there was abundant Ki-67 and iododeoxyuridine staining of B-lymphocytes in germinal centers in PET-positive lymph nodes, explaining the high rate of false-positive findings. The sensitivity, specificity, positive predictive value, and negative predictive value of (18)F-FLT PET were 100%, 16.7%, 37.5%, and 100%, respectively. In head and neck cancer patients, (18)F-FLT PET showed uptake in metastatic as well as in nonmetastatic reactive lymph nodes, the latter due to reactive B-lymphocyte proliferation. Because of the low specificity, (18)F-FLT PET is not suitable for assessment of pretreatment lymph node status. This observation may also negatively influence the utility of (18)F-FLT PET for early treatment response evaluation of small metastatic nodes.

Lesions associated with Mycobacterium tuberculosis complex infection in the European wild boar

Information on lesion distribution and characteristics is essential to determine the significance of a species as a reservoir host for tuberculosis (TB). Herein, we describe the extension and distribution of lesions in 127 Mycobacterium tuberculosis Complex culture positive European wild boars (Sus scrofa), and use this information to discuss the role of this wildlife species in TB epidemiology in Mediterranean Spain. Macroscopic TB-compatible lesions were detected in 105 of 127 wild boars (82.68%). Only microscopic lesions were found in 11 wild boars (8.66%). Lesions were not evident in 11 wild boars (8.66%). A total of 49 wild boars had lesions confined to one anatomical region (42.2%, localized TB), while 67 animals had lesions in more than one anatomical region (57.8%, generalized TB). Head lymph nodes (LNs), particularly the mandibular LNs, were most frequently affected (107/116, 92.24%), and 43 wild boar had only mandibular LN lesions. Histopathology evidenced TB lesions in 38.1% of the lungs, 23% of the livers and 13% of the spleens examined. Mammary gland lesions were observed in three cases. When TB lesions were localized, granulomas characterized by a mixed inflammatory cell population were more predominant, whereas strongly necrotic-calcified granulomas were more prevalent in generalized cases of TB infection. Large lesions in more than one anatomical region were more frequent among juveniles. The histopathological characteristics of the tuberculous reaction and the associated tissue damage in various organs, together with the gross pathology, indicate that at least those wild boar with large lesions and generalized infections have the potential to excrete mycobacteria by several routes. This finding, in the context of unusually high densities of wild boar and fencing and feeding, reinforces the suggestion that wild boar can act as a true TB reservoir under the particular circumstances of Mediterranean Spain. Further studies on the routes of excretion as well as the effect of altering management methods would be of interest to confirm the role of wild boar in TB epidemiology in Spain.

Comparison of the efficacy of clinical examination, ultrasound neck and computed tomography in detection and staging of cervical lymph node metastasis in head and neck cancers

There are many modalities, which are being used for detection of cervical lymph nodes in head and neck cancers clinical examination, computed tomography, ultrasound, magnetic resonance imaging and radionuclide scintigraphy. Various studies in past have highlighted their benefits and drawbacks used singly or in comparison with others. Here we present the study of 100 patients comparing the result of clinical examination, computed tomography and ultrasound.

Imaging of Lymph Nodes in the Head and Neck Region

SummaryThis paper describes the modern imaging methods, techniques, ability and performance in detecting and staging head and neck lymph nodes. Furthermore, the imaging morphologies of benign and malignant lymph nodes according to the different imaging techniques are shown. The imaging techniques of ultrasonography, computed tomography and magnetic resonance imaging (MRI) including diffusion‐weighted imaging and contrast‐enhanced iron oxide MRI are explained. Imaging examples of the different modalities of benign‐ and malignant‐transformed lymph nodes are shown. Additionally, the diagnostic sensitivity of each modality are delineated and further aspects of modern lymph node staging of the head and neck region, such as those with special contrast agents are described. These modern imaging modalities have sensitivity rates of 70–80% depending on the technical equipment and ability and on the experience of the investigator. The value of biopsy techniques including recently developed ultrasonography guided needle biopsy with molecular analysis of the cells of about 97–100% accuracy in diagnosing benign from malignant lymph nodes are mentioned. Overall, the reader gets an overview of the present imaging modalities to potentially stage correctly lymph nodes in the head and neck region to facilitate the therapeutic procedure.

Modern imaging lymph node staging of the head and neck region

The aim of this paper is to describe the modern imaging methods, their techniques, ability, and performance in staging head and neck lymph nodes. Also, the imaging morphologies of benign and malignant lymph nodes according to the different imaging techniques will be delineated.

Mycobacterial and Rhodococcus equi infections in pigs in the Czech Republic between the years 1996 and 2004: the causal factors and distribution of infections in the tissues

Between 1996 and 2004, tissue samples from 3&amp;nbsp;630 slaughtered pigs were examined by gross examination, microscopy after the Ziehl-Neelsen (ZN) staining of homogenised tissues for the detection of acid-fast rods (AFR) and by culture for the presence of mycobacteria and Rhodococcus equi: 1&amp;nbsp;781 head lymph nodes (ln), 1&amp;nbsp;123&amp;nbsp;mesenteric ln, 54 pulmonary ln, 32 inguinal ln, 562 non-identified ln and 78 samples of tissues from parenchymatous organs (liver, spleen and kidneys). Tuberculous/tuberculoid lesions were not detected in 249 (6.9%) animals slaughtered due to a positive response to avian tuberculin. Various gross lesions were detected in 3&amp;nbsp;381 (93.1%) animals as follows: adenopathy in 150 (4.1%), tuberculous lesions with caseation in 2&amp;nbsp;026 (55.8%) and tuberculous lesions with calcification in 1&amp;nbsp;205 (33.2%) of them. AFR were found in tissues from 2&amp;nbsp;047 (56.4%) animals: in 36&amp;nbsp;(14.5%) animals free from gross lesions, in 28 (18.7%) animals with adenopathy, in 801 (39.5%) animals with caseation and in 913 (75.8%) animals with calcified tuberculous lesions. Mycobacteria were isolated from the tissues of 289 (15.8%) of 1&amp;nbsp;852 animals without detected AFR and from the tissues of 1 290 (72.5%) of the 1&amp;nbsp;778 animals with detected AFR of various intensities. Of 1&amp;nbsp;579 mycobacterial isolates 1&amp;nbsp;493 (94.6%) were classified as M.&amp;nbsp;avium complex (MAC) members: 469 (29.7%) M.&amp;nbsp;a.&amp;nbsp;avium (IS901+, serotypes 1, 2, and 3) and 891&amp;nbsp;(56.4%) M.&amp;nbsp;a.&amp;nbsp;hominissuis (IS901&amp;ndash;) isolates of serotypes 4 (n&amp;nbsp;=&amp;nbsp;1), 8 (n&amp;nbsp;=&amp;nbsp;643), 9 (n&amp;nbsp;=&amp;nbsp;74) and non-typed (n&amp;nbsp;=&amp;nbsp;173). The other 52 (3.3%) isolates were members of other mycobacterial species: M.&amp;nbsp;chelonae (n&amp;nbsp;=&amp;nbsp;35), M.&amp;nbsp;smegmatis (n&amp;nbsp;=&amp;nbsp;4), M.&amp;nbsp;xenopi (n&amp;nbsp;=&amp;nbsp;3), M.&amp;nbsp;terrae (n&amp;nbsp;=&amp;nbsp;7), M.&amp;nbsp;aurum (n&amp;nbsp;=&amp;nbsp;1), M.&amp;nbsp;scrofulaceum (n&amp;nbsp;=&amp;nbsp;1), M. fortuitum (n = 1) and biochemically non-identified mycobacteria (n&amp;nbsp;=&amp;nbsp;34). By examination of ZN stained homogenised tissues, AFR were detected significantly more frequently (P &amp;lt; 0.01) in samples from animals with caseated and/or calcified tuberculous lesions than in tissues from animals without tuberculous lesions. The detection rate of isolates from tissues with tuberculous lesions was likewise significantly higher (P &amp;lt; 0.01) than from tissues without tuberculous lesions.

Experimental Vesicular Stomatitis Virus Infection in Horses: Effect of Route of Inoculation and Virus Serotype

Horses were inoculated with Vesicular stomatitis New Jersey and Indiana viruses by routes simulating contact and vector transmission. Clinical signs, lesions, antibody development, viral shedding and persistence, and viremia were monitored. Horses were infected with both viruses by all routes as confirmed by seroconversion. Salivation, primary lesions at inoculation sites, and secondary oral lesions were the most common clinical findings. Viral shedding was most often from the oral cavity, followed by the nasal cavity; titers were highest from oral cavity samples. Virus was rarely isolated from the conjunctival sac and never from feces or blood. Development of neutralizing antibody coincided with cessation of lesion development and detection of virus by isolation. Circulating virus-specific IgM, IgG, IgA, and neutralizing antibodies developed in most animals postinoculation (PI) days 6 to 12, depending on the route of inoculation. At postmortem (PI days 12 to 15), lesions were healing, were not vesicular, and did not contain detectable virus by isolation, reverse transcriptase polymerase chain reaction, or immunohistochemistry. Numerous infiltrating lymphocytes and plasma cells suggested that lesion resolution was partially due to local immunity. Detection of viral RNA from tonsil and lymph nodes of head at necropsy suggests that these tissues play a role in the pathogenesis of the disease; molecular techniques targeting these tissues may be useful for confirming infection in resolving stages of disease. The routes of inoculation used in this study reflect the diversity of transmission routes that may occur during outbreaks and can be used to further study contact and vector transmission, vaccine development, and clarify pathogenesis of the disease in horses.

Reappraisal of metastatic lymph node topography in head and neck squamous cell carcinomas

To analyze the lymphatic distribution of metastatic carcinomatous cells in cervical lymph nodes in head and neck squamous cell carcinoma (HNSCC). We retrospectively reviewed 119 patients treated in our hospital for HNSCC (1999-2004). Topography of the neck dissection specimens was prospectively classified according to the classification of Robbins. The 4000 lymph nodes were analyzed by optical microscopy using hematoxylin-eosin-safran (HES) staining. In cases of negative results in level II, cytokeratin (AE1/AE3) immunodetection was performed. Metastases were visualized using HES in 6.4% of lymph nodes for oral cavity, and 4.7% of oropharyngeal, 4.4% of hypopharyngeal, and 1.3% of endolaryngeal cancers. The highest incidence of nodal metastasis was observed in level IIa (P < 0.01). In eight patients (6.7%) with lymph node metastases, level II was spared. In these patients, all 134 nodes histologically negative on HES were confirmed to be negative by IHC. Level IIa is the main level involved in regional metastases of HNSCC, regardless of the primary site of cancer. However, in eight (6.7%) patients, level II was spared, as confirmed by IHC. In these cases, level II did not represent the first step of drainage from the tumor. The sentinel lymph node technique in HNSCC is discussed in light of these results.

Cervical duct cannulation in sheep for collection of afferent lymph dendritic cells from head tissues

Pseudo-afferent cervical lymph-duct cannulation in a sheep model allows large amounts of lymph cells to be collected under physiological conditions, carrying immune signaling information from the head tissues, including oro-nasal mucosae. Importantly, large quantities of dendritic cells (DCs) of several subtypes are obtained (up to 8 million per overnight collection), as well as many other trafficking leukocytes. The technique includes three steps: removal of all head lymph nodes on one side (2 h), catheterization of cervical lymph ducts after 2 months (2-3 h) and collection/purification of lymph-cell subsets (4 h). The approach is challenging (1 in 3 success rate) but fruitful, and can be used to study DC subsets under immunomodulation, in order to assess lymph-cell subset dynamic changes and antigen transportation from oro-nasal tissues. This protocol is directed to experienced postdoctoral researchers.

Modern imaging lymph node staging of the head and neck region

The aim of this paper is to describe the modern imaging methods, their techniques, ability, and performance in staging head and neck lymph nodes. Also, the imaging morphologies of benign and malignant lymph nodes according to the different imaging techniques will be delineated. The imaging techniques of ultrasound including contrast-enhanced ultrasound, computed tomography and magnetic resonance imaging (MRI) including diffusing weighted imaging and contrast-enhanced iron oxide MRI are explained. Imaging examples of the different modalities of benign and malignant transformed lymph nodes will be demonstrated. Furthermore, the diagnostic sensitivity of each modality will be delineated and further aspects of modern lymph node staging of the head and neck region such as those with special contrast agents will be described. These modern imaging modalities have sensitivity rates of 70–80% depending on the technical equipment and ability and on the experience of the investigator. The technique of near-infrared-imaging will be mentioned in another article in this journal. Also the value of biopsy techniques including recently developed ultrasonography guided needle biopsy with molecular analysis of the cells of about 97–100% accuracy in diagnosing benign from malignant lymph nodes will be mentioned. Overall, the reader will get an overview of the present imaging modalities to potentially stage correctly lymph nodes in the head and neck region to facilitate the therapeutic procedure.

Operative surgery. Head and neck and lymph nodes. Edited by Maurice Ewing, M.Sc., F.R.C.S., F.R.C.S. (Edin.), F.R.A.C.S., F.A.C.S., Melbourne. Second edition. Volume 6. 10¾ × 8½ in. Pp. 254 + xiv. Illustrated. London: Butterworth &amp; Co. (Publishers) Ltd. Vols. 1–6, subtitled General Surgery: £50. Full 14-volume set: £97

Operative surgery. Head and neck and lymph nodes. Edited by Maurice Ewing, M.Sc., F.R.C.S., F.R.C.S. (Edin.), F.R.A.C.S., F.A.C.S., Melbourne. Second edition. Volume 6. 10¾ × 8½ in. Pp. 254 + xiv. Illustrated. London: Butterworth &amp; Co. (Publishers) Ltd. Vols. 1–6, subtitled General Surgery: £50. Full 14-volume set: £97

The nodal neck level of sentinel lymph nodes in mucosal head and neck cancer

Sentinel node biopsy is emerging as a successful means of identifying subclinical lymph node disease in mucosal head and neck cancer. Sentinel node studies in melanoma and breast cancer have identified sentinel nodes at unusual sites and the technique is redefining our understanding of dynamic lymphatic flow. In this study, the sentinel nodes in mucosal head and neck malignancies were mapped according to their site within the neck and this was correlated with tumour site within the oral cavity. Fifty-two necks were explored for sentinel nodes from tumours located in the tongue (23 cases), floor of mouth (12 cases), palate (six cases), retromolar trigone (five cases), alveolus (three cases), buccal mucosa (two cases), tonsil (two cases) and lip (one case). In total, 124 sentinel nodes were found in levels I-V. Two hot spots were found in the tonsils and were not excised, two nodes were located in level IIB, four nodes were found in level IV, three in the contralateral neck and one in level V. The sentinel nodes located at unusual sites would not have been excised in a supraomohyoid neck dissection and the study has improved our understanding of dynamic lymph flow from tumours.

Treatment results on advanced neck metastasis (N3) from head and neck squamous carcinoma

To analyze the long-term results of patients with N3 neck metastasis from squamous carcinoma of the head and neck. This study is based on the analysis of a retrospective cohort of 224 previously untreated patients with squamous cell carcinoma of the head and neck and lymph node metastasis sized greater than 6 cm (N3) who were evaluated from 1981 to 1996. Fifty-four patients (24.1%) underwent neck dissection, 137 underwent radiotherapy alone (61.2%), and 33 received only supportive care (14.7%). Control of the neck metastasis was achieved in 46 cases among the treated ones (24.1%), varying from 51.9% for the patients who underwent surgery to 13.1% for radiotherapy alone ( P < 0.001). Exclusive distant metastasis occurred in 37.0% of the cases who had control of the neck disease. The 3-year overall survival rates were 17.9% for patients who underwent surgery and 7.0% for radiotherapy alone ( P = 0.003). The multivariate analysis showed as independent predictive factors the treatment approach ( P < 0.001) and tumor site ( P = 0.016). This study confirms the poor prognosis of patients with N3 neck disease, mainly when treated by radiotherapy alone. A radical neck dissection associated with adjuvant radiotherapy is indicated whenever feasible. Because of the high rate of distant metastasis, protocols including adjuvant chemotherapy should be investigated.

Utilization and outcome of radiotherapy among patients with limited stage indolent follicular lymphoma in the United States

6642 Background: Radiotherapy is frequently advocated as a standard therapy for patients with limited stage follicular small cleaved lymphoma (FSC) and follicular mixed small and large cell lymphoma (FM). Long-term analysis of institutional series have demonstrated one-third to one-half of patients have prolonged relapse free survival. Methods: This retrospective review of the SEER-9 database was conducted to determine the frequency and outcome of radiotherapy administration as part of the first course of treatment among a population-based cohort. ICD-O-2 diagnostic morphology codes were used to identify a cohort of patients with limited stage FSC and FM, diagnosed between 1983 and 2001. Results: A cohort of 3,165 patients was identified from nine SEER registries. The cohort was comprised of 1,687 (53.3%) females, 1,822 (57.9%) FSC, and 1,326 (42.1%) FM. The most frequent anatomic sites of presentation included head and cervical lymph nodes (37.2%), inguinal lymph nodes (22.0%), axillary lymph nodes (9.8%...

Distribution of Mycobacterium avium complex isolates in tissue samples of pigs fed peat naturally contaminated with mycobacteria as a supplement.

In early 1999, there was an increased incidence of tuberculous lesions in the lymph nodes of slaughtered pigs in the Czech Republic. In part 1 of this study, tuberculous lesions were detected in 140 (62%) tissue samples collected from pigs coming from 15 farms in 15 districts at routine veterinary meat inspections in abattoirs. Mycobacteria were isolated from 37 (16%) tissue samples: 34 Mycobacterium avium subsp. hominissuis isolates and three environmentally derived mycobacteria. In search of infection sources, M. avium subsp. hominissuis was isolated from 38 (79%) samples of peat used as a feed supplement. In part 2 of our study, the head, mesenteric, and inguinal lymph nodes of 117 randomly selected slaughtered pigs from one farm with young piglets fed peat as a supplement were investigated for mycobacterial infection. From 65 (56%) pigs, a total of 76 mycobacterial isolates were identified (56 M. avium subsp. hominissuis isolates, 5 M. avium subsp. avium isolates, 3 M. intracellulare isolates, and 12 environmentally derived mycobacterial isolates). IS1245 restriction fragment length polymorphism (RFLP) types with >20 bands of 45 distinct RFLP types were found in 49 M. avium subsp. hominissuis isolates from pigs (n = 31) and peat (n = 18). Identical RFLP types were found in only four pig isolates. Five randomly selected isolates from pigs and peat were subcultured to six independent clones or colonies. Among the IS1245 RFLP types of 30 clones, identical RFLP types obtained from pigs and peat were identified, which confirmed the hypothesis that peat contaminated with mycobacteria represents a significant source of mycobacterial infection for pigs.