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Head and neck paragangliomas (HNPGLs), rare neuroendocrine tumors that mainly arise from parasympathetic ganglia along the cranial nerves, are challenging due to anatomic origin, tendency to aggressive neurovascular and skull base infiltration, unpredictable metastatic potential, radio-chemoresistance, and risk of multiplicity. Symptoms range from mild to life threatening depending on location/size, but rarely relate to catecholamine excess. Risk factors include female sex and pathogenic germline variants in genes affecting hypoxia signaling (foremost succinate dehydrogenase genes). Diagnostic work-up relies on imaging, measurements of plasma free metanephrines/methoxytyramine, genetic testing, and pathology/immunohistochemistry. Management is tailored to patient/tumor characteristics and encompasses wait-scan, upfront surgery, debulking surgery, and radiotherapy. Presurgical embolization is recommended, except for small tympanic and tympanomasoid tumors. Presurgical stenting is required for internal carotid artery involvement, and two-stage surgery for intradural extension. Current treatments for metastatic/inoperable HNPGL are non-curative, and long-term follow-up should be recommended for all patients to monitor local recurrence and new tumors., (Copyright © 2024. Published by Elsevier Ltd.)

In total, ~25% of familial breast cancer (BC) is attributed to germline mutations of the BRCA1 and BRCA2 genes, while the rest of the cases are included in the BRCAX group. BC is also known to affect men, with a worldwide incidence of 1%. Epigenetic alterations, including DNA methylation, have been rarely studied in male breast cancer (MBC) on a genome-wide level. The aim of the present study was to examine the global DNA methylation profiles of patients with BC to identify differences between familial female breast cancer (FBC) and MBC, and according to BRCA1, BRCA2 or BRCAX mutation status. The genomic DNA of formalin-fixed paraffin-embedded tissues from 17 women and 7 men with BC was subjected to methylated DNA immunoprecipitation and hybridized on human promoter microarrays. The comparison between FBC and MBC revealed 2,846 significant differentially methylated regions corresponding to 2,486 annotated genes. Gene Ontology enrichment analysis revealed molecular function terms, such as the GTPase superfamily genes (particularly the GTPase Rho GAP/GEF and GTPase RAB), and cellular component terms associated with cytoskeletal architecture, such as 'cytoskeletal part', 'keratin filament' and 'intermediate filament'. When only FBC was considered, several cancer-associated pathways were among the most enriched KEGG pathways of differentially methylated genes when the BRCA2 group was compared with the BRCAX or BRCA1+BRCAX groups. The comparison between the BRCA1 and BRCA2+BRCAX groups comprised the molecular function term 'cytoskeletal protein binding'. Finally, the functional annotation of differentially methylated genes between the BRCAX and BRCA1+BRCA2 groups indicated that the most enriched molecular function terms were associated with GTPase activity. In conclusion, to the best of our knowledge, the present study was the first to compare the global DNA methylation profile of familial FBC and MBC. The results may provide useful insights into the epigenomic subtyping of BC and shed light on a possible novel molecular mechanism underlying BC carcinogenesis., Competing Interests: The authors declare that they have no competing interests., (Copyright: © Abeni et al.)

In this review, we propose that paraganglioma is a fundamentally organized, albeit aberrant, tissue composed of neoplastic vascular and neural cell types that share a common origin from a multipotent mesenchymal-like stem/progenitor cell. This view is consistent with the pseudohypoxic footprint implicated in the molecular pathogenesis of the disease, is in harmony with the neural crest origin of the paraganglia, and is strongly supported by the physiological model of carotid body hyperplasia. Our immunomorphological and molecular studies of head and neck paragangliomas demonstrate in all cases relationships between the vascular and the neural tumor compartments, that share mesenchymal and immature vasculo-neural markers, conserved in derived cell cultures. This immature, multipotent phenotype is supported by constitutive amplification of NOTCH signaling genes and by loss of the microRNA-200s and -34s, which control NOTCH1 , ZEB1 , and PDGFRA in head and neck paraganglioma cells. Importantly, the neuroepithelial component is distinguished by extreme mitochondrial alterations, associated with collapse of the ΔΨm. Finally, our xenograft models of head and neck paraganglioma demonstrate that mesenchymal-like cells first give rise to a vasculo-angiogenic network, and then self-organize into neuroepithelial-like clusters, a process inhibited by treatment with imatinib.

Tumours can be viewed as aberrant tissues or organs sustained by tumorigenic stem-like cells that engage into dysregulated histo/organogenetic processes. Paragangliomas, prototypical organoid tumours constituted by dysmorphic variants of the vascular and neural tissues found in normal paraganglia, provide a model to test this hypothesis. To understand the origin of paragangliomas, we built a biobank comprising 77 cases, 18 primary cultures, 4 derived cell lines, 80 patient-derived xenografts and 11 cell-derived xenografts. We comparatively investigated these unique complementary materials using morphofunctional, ultrastructural and flow cytometric assays accompanied by microRNA studies. We found that paragangliomas contain stem-like cells with hybrid mesenchymal/vasculoneural phenotype, stabilized and expanded in the derived cultures. The viability and growth of such cultures depended on the downregulation of the miR-200 and miR-34 families, which allowed high PDGFRA and ZEB1 protein expression levels. Both tumour tissue- and cell culture-derived xenografts recapitulated the vasculoneural paraganglioma structure and arose from mesenchymal-like cells through a fixed developmental sequence. First, vasculoangiogenesis organized the microenvironment, building a perivascular niche which in turn supported neurogenesis. Neuroepithelial differentiation was associated with severe mitochondrial dysfunction, not present in cultured paraganglioma cells, but acquired in vivo during xenograft formation. Vasculogenesis was the Achilles' heel of xenograft development. In fact, imatinib, that targets endothelial-mural signalling, blocked paraganglioma xenograft formation (11 xenografts from 12 cell transplants in the control group versus 2 out of 10 in the treated group, P = 0.0015). Overall our key results were unaffected by the SDHx gene carrier status of the patient, characterized for 70 out of 77 cases. In conclusion, we explain the biphasic vasculoneural structure of paragangliomas and identify an early and pharmacologically actionable phase of paraganglioma organization.

The given and family names of two co-authors were incorrect in the published article. The correct spelling should read as: Sampath Chandra Prasad and Vinagolu K Rajasekhar.

In melanoma, a number of specific genetic and genomic aberrations have been identified to be important in tumorigenesis. In particular, the mutant B-Raf proto-oncogene, Serine/Threonine kinase (BRAF) gene is the target of tailored therapy with kinase inhibitor molecules. Identification of the array of mutations in patients with melanoma will be useful in determining a genetic profile of the tumor with potential implications for treatment decisions. A rare aminoacidic insertion in codon 599 of the BRAF gene (c.1797_1798insACA, T599insT) was detected by using both direct (Sanger) sequencing and pyrosequencing techniques in a metastatic melanoma of a female elderly patient. As suggested in other clinical contexts including pilocytic astrocytoma, papillary thyroid carcinomas and anaplastic thyroid carcinomas, this unusual mutation may be associated with a modified spatial structure of activated P-loop, resulting in a constitutional activation of the BRAF protein. The patient died shortly following the test, thus no biological therapy was performed. Comparable data regarding treatment of melanoma patients with rare BRAF mutations is lacking, and the response to BRAF inhibitors requires further investigation.

Background: Primary squamous cell carcinoma (SCC) of the breast is a rare and aggressive neoplasm that constitutes approximately 0.1% of all breast carcinomas. Before the tumor can be classified as a true SCC of the breast, certain criteria need to be fulfilled. These are: i) more than 90% of the malignant cells must be of squamous cells origin; ii) tumor is independent from the overlying skin and nipple; iii) other sites of primary SCC have been excluded., Case Report: We describe a case of pure SCC of the breast that arose 15 years after local radiation for a primary adenocarcinoma of the breast in a 54-year-old woman with history of bilateral breast cancer. The tumor was triple-negative with a high Ki-67 index. The patient underwent adjuvant chemotherapy with docetaxel and oral fluorouracil., Conclusion: There are no specific guidelines for the treatment of primary SCC of the breast. Larger series are necessary to determine if different strategies of treatment and follow-up are necessary and if prognosis is really comparable to other histotypes of cancers of the breast., (Copyright © 2014 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)

Choristoma of the middle ear is a rare condition characterized by the presence of normal salivary gland tissue in the middle ear space. Salivary gland choristomas are benign lesions that are frequently associated with ossicular chain and facial nerve anomalies. Total surgical excision is indicated when there is no risk of damaging the facial nerve. We describe a new case of salivary gland choristoma of the middle ear, and we discuss the etiology, histologic features, and management of such lesions. Our patient was a 22-year-old woman in whom we surgically removed a whitish retrotympanic mass. Intraoperatively, we also detected an ossicular chain malformation. Histologic examination of the choristoma revealed the presence of salivary gland tissue. Furthermore, the lesion contained an extensive and previously undescribed component: a well-defined pseudostratified respiratory-type epithelium, similar to that of a normal eustachian tube. Ten months after removal of the choristoma, we surgically repaired the ossicular chain anomalies. No recurrence was noted on follow-up.

Objective: To study the clinical features, tumor characteristics and outcomes of giant cell tumors (GCTs) in the skull base based on long-term follow-up. We also report the largest series of GCTs in the temporal bone and the lateral skull base., Materials and Methods: A retrospective study was conducted of all GCTs managed at the Gruppo Otologico, a quaternary referral skull base institute, in Italy from 1993 to 2013. The clinical features, investigations, surgical management and follow-up were recorded. The surgical approaches used were infratemporal fossa approach (ITFA) type B and D and middle cranial fossa (MCF) approaches., Results and Observations: A total of 7 patients with GCTs of the skull base were treated at our institution. The principal complaints were hearing loss reported in 6 (85.71%) patients, tinnitus in 5 (71.43%) and swelling in 3 (42.9%). Pure-tone audiometry showed conductive hearing loss in 5 (71.43%) patients. High-resolution CT scan and MRI with gadolinium enhancement were done in all patients. Radiology showed involvement of the ITF and middle ear in 6 (85.71%) patients each, temporomandibular joint in 4 (57.14%) patients, invasions of the squamous part of the temporal bone, mastoid, MCF and greater wing of sphenoid in 3 (42.9%) patients each and the petrous bone in 2 (28.6%) patients. ITFA type B was applied as an approach for tumor removal in 5 (71.43%) patients, including a case where an additional MCF approach was employed, and ITFA type D and the transmastoid approach were applied in 1 (14.3%) patient each. Total tumor removal and successful cure was achieved in 6 (85.71%) patients. Subtotal removal leading to recurrence and eventual mortality was the result in 1 (14.3%) patient., Conclusions: A thorough knowledge of the anatomy of the skull base and the various skull base approaches is necessary to tackle GCTs. ITFA type B and D combined with MCF approaches provide good exposure of the tumor with minimal postoperative sequelae and good locoregional control. Recurrence due to either subtotal removal or suboptimal treatment may have disastrous consequences for the patient.

Objective: Endolymphatic sac tumor (ELST) is a rare low grade adenocarcinoma of the skull base. During the past decade the number of the reported cases has increased. This study exposes our experience in the management of ELST with a review of the literature., Study Design: Retrospective study of patients with ELST at a quaternary referral otology and skull base center., Methods: A review of the records from the Gruppo Otologico revealed 7 patients treated for ELST. All papers containing series of three or more cases of ELST published in the English literature were selected for analysis., Results: Hearing loss and tinnitus were present in almost all our cases. All of them were evaluated with audiometric tests, computed tomography and magnetic resonance imaging. All the patients were treated surgically with preservation of the facial nerve and preoperative embolization was performed in 5 patients. Genetic study was performed on all our cases and revealed the presence of von Hippel-Lindau syndrome in one patient who had the tumor as the initial manifestation of his syndrome. None of the patients received postoperative radiotherapy and one of them had recurrence of the tumor 13 years following surgery., Conclusions: Complete surgical resection with preoperative embolization of large tumors is the mainstay treatment for ELST. The facial nerve should not be sacrificed unless it is totally invaded by the tumor. A long term follow up is recommended and the role of postoperative adjunctive radiotherapy is still controversial., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Objectives/hypothesis: A relation between conventional radiotherapy and the development of intracranial neoplasma is well known, but radiation-associated tumor following stereotactic radiotherapy of vestibular schwannoma is underestimated. In this article we will study this relation by doing a complete literature review on all the malignant intracranial tumors that appeared following radiosurgery and adding a case of malignant vestibular schwannoma following stereotactic radiotherapy in a Neurofibromatosis type 2 patient., Methods: Literature review and discussion., Results: We found 26 cases of malignant brain tumor following stereotactic radiotherapy including our case. In 13 cases the tumor occurred in context of Neurofibromatosis type 2. None of the patients had a tumor size less than 2.5 cm. and the mean latency period between the radiotherapy and malignant tumor development was 5.8 years., Conclusion: Patients with vestibular schwannoma should be made aware of the low incidence of the radiation-induced malignant changes and long-term follow-up is mandatory., (Copyright © 2011 The American Laryngological, Rhinological, and Otological Society, Inc.)

Background: CD4(+) regulatory T cells are a specialized subset of T cells that actively control immune responses. Several experimental protocols have been used to expand natural regulatory T cells and to generate adaptive type 1 regulatory T cells for regulatory T-cell-based therapies., Design and Methods: The ability of exogenous recombinant human interleukin-10 to induce alloantigen-specific anergy in T cells was investigated and compared to that of interleukin-10 derived from tolerogenic dendritic cells, in mixed lymphocyte cultures. A detailed characterization of the effector functions of the resulting anergized T cells is reported., Results: Interleukin-10, whether exogenous or derived from tolerogenic dendritic cells, induces a population of alloantigen-specific T cells (interleukin-10-anergized T cells) containing type 1 regulatory T cells, which are anergic and actively suppress alloantigen-specific effector T cells present within the mixed population. Interleukin-10-induced anergy is transforming growth factor-β independent, and is associated with a decreased frequency of alloantigen-specific cytotoxic T lymphocyte precursors, but interleukin-10-anergized T cells are still responsive to third-party, bacterial, and viral antigens. Tolerogenic dendritic cells are more powerful than exogenous interleukin-10 in generating type 1 regulatory T-cell precursors, and are also effective in the context of HLA-matched donors., Conclusions: Based on these studies, we have developed an efficient and reproducible in vitro method to generate antigen-specific type 1 regulatory T-cell precursors starting from total peripheral blood cells with minimal cell manipulation and suitable for generating type 1 regulatory T cells for regulatory T-cell-based therapies.

All of the members of the peripheral primitive neuroectodermal tumor family (Ewing sarcomas, neuroectodermal tumors of bone, peripheral neuroepitheliomas, and Askin tumors) have similar morphologic and immunophenotypical features (ie, the proliferation of small and medium-sized round cells in a fibrous background showing strong and diffuse immunohistochemical positivity for CD99), and the common cytogenetic abnormality of a nonrandom translocation involving the EWS gene and one of several members of the erythroblastosis virus transforming sequence family of transcription factors. The combination of clinical information and morphologic/immunophenotypical characteristics is usually sufficient for a correct diagnosis, but there are rare cases in which an unusual predominant or multidirectional immunophenotypical differentiation makes diagnosis a challenge and requires the use of molecular cytogenetic or molecular techniques. We describe 3 such cases in which we employed fluorescence in-situ hybridization analysis to detect translocation involving the EWS gene and reverse transcription polymerase chain reaction followed by sequencing to detect the fusion transcript EWS-FLI1.

In the era of antiretroviral therapy, liver disease has emerged as an important cause of morbidity and mortality in HIV/hepatitis C virus (HCV) coinfected patients. It is believed that HCV is a non-cytopathic virus and that T-cell-mediated events (including the production of pro-inflammatory cytokines) have an important role in promoting both liver damage and viral clearance. Whether HIV coinfection or antiretroviral therapies influence such events is still unclear. In the current study, we compared the expression of NKp46 (a natural killer cell marker), CD3 (a T-cell marker), interferon-gamma (IFN-gamma), tumour-necrosis factor-alpha (TNF-alpha; pro-inflammatory cytokines) and interleukin-10 (IL-10; an anti-inflammatory cytokine) mRNA in the liver of naive HIV/HCV-coinfected patients (group one, n=14), coinfected patients treated with antiretroviral therapy (group two, n=23) and naive HCV mono-infected patients (group three, n=24). All three groups had comparable HCV viremia, with coinfected patients showing similar and relatively high CD4+ T-cell counts and significantly different HIV vireamia. Interestingly, when compared to groups two and three, group one showed significantly higher intrahepatic mRNA levels for CD3, IFN-gamma and TNF-alpha, whereas the expression of NKp46 and IL-10 were comparable in all three groups. Further, higher histopathological grading scores within each group were independently associated with higher mRNA contents for CD3 and IFN-gamma and higher serum alanine aminotransferase levels at the time of liver biopsy. Together, these results suggest that HIV infection may exacerbate the immune-mediated inflammatory response in the liver of patients chronically infected with HCV and antiretroviral therapy may prevent this effect.

Background: Gefitinib, a specific epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, has activity against approximately 10% of unselected non-small-cell lung cancer (NSCLC) patients. Phosphatidylinositol 3'-kinase (PI3K)/Akt and Ras/Raf/mitogen-activated protein kinase (MAPK), the two main EGFR-signaling pathways, mediate EGFR effects on proliferation and survival. Because activation of these pathways is dependent on the phosphorylation status of the components, we evaluated the association between phosphorylation status of Akt (P-Akt) and MAPK (P-MAPK) and gefitinib activity in patients with advanced NSCLC., Methods: Consecutive patients (n = 106) with NSCLC who had progressed or relapsed on standard therapy received gefitinib (250 mg/day) until disease progression, unacceptable toxicity, or patient refusal. P-Akt and P-MAPK positivity was determined with immunohistochemistry using tumor tissues obtained before any anticancer treatment. Association of P-Akt and time to progression was determined by univariable and multivariable analyses. All statistical tests were two-sided., Results: Of the 103 evaluable patients, 51 (49.5%) had tumors that were positive for P-Akt, and 23 (22.3%) had tumors that were positive for P-MAPK. P-Akt-positivity status was statistically significantly associated with being female (P<.001), with never-smoking history (P =.004), and with bronchioloalveolar carcinoma histology (P =.034). Compared with patients whose tumors were negative for P-Akt, patients whose tumors were positive for P-Akt had a better response rate (26.1% versus 3.9%; P =.003), disease control rate (60.9% versus 23.5%; P<.001), and time to progression (5.5 versus 2.8 months; P =.004). Response rate, disease control rate, and time to progression did not differ according to P-MAPK status. The multivariable analysis showed that P-Akt positivity was associated with a reduced risk of disease progression (hazard ratio = 0.58, 95% confidence interval = 0.35 to 0.94)., Conclusions: Patients with P-Akt-positive tumors who received gefitinib had a better response rate, disease control rate, and time to progression than patients with P-Akt-negative tumors, suggesting that gefitinib may be most effective in patients with basal Akt activation.

Purpose: To evaluate the correlation between HER2 expression and gefitinib (ZD 1839, Iressa; AstraZeneca, London, United Kingdom) efficacy in terms of response rate, time to progression (TTP), and overall survival (OS) time., Patients and Methods: Patients with pretreated advanced non-small-cell lung cancer (NSCLC) received gefitinib at a daily dose of 250 mg until disease progression. Tumor tissue specimens obtained at the time of primary diagnosis were collected to determine HER2/epidermal growth factor receptor (EGFR) status by immunohistochemistry., Results: From February 2001 to June 2002, 63 consecutive patients were enrolled onto the study. The overall disease control rate was 58.7% (partial response [PR], 15.9%; stable disease [SD], 42.8%), median TTP was 3.3 months, and median OS was 4.1 months. Among the 43 patients in whom EGFR/HER2 status was determined, we observed six PRs (14%) and 18 SDs (42%). Disease control, including PR and SD, was 40% in the 15 patients overexpressing HER2 and 64.3% in the 28 patients not overexpressing HER2 (P =.126). No difference was found between the two groups in terms of TTP (3.5 v 3.7 months, respectively) and OS (5.7 v 6.8 months, respectively). In addition, we did not find any difference in TTP, OS, toxicity, and symptom outcome in the group of patients overexpressing both HER2 and EGFR compared with patients who had no overexpression of HER2, Conclusion: According to these data, efficacy, toxicity, and symptom outcome in patients with NSCLC treated with gefitinib do not seem to be related to HER2 expression.

Acute renal failure due to idiopathic tubulo-interstitial nephritis associated with bilateral uveitis (TINU syndrome) is a rare clinical event, contracted mainly by girls or women. Here we report the clinical follow-up regarding a 22-year-old woman with acute renal failure (creat. clearance 13.5 ml/min) due to idiopathic tubulo-interstitial nephritis documented by renal biopsy, after bilateral uveitis which healed with local prednisone. The clinical history and the clinical follow-up of our patient were typical of the TINU syndrome. We were able to exclude all diseases causing acute tubulo-interstitial nephritis such as systemic infection, hypersensitivity to drugs, Behcet's disease, Sjogren syndrome, sarcoidosis, systemic lupus or vasculitides. The patient recovered after systemic prednisone.

This paper is a report on a case of gastric carcinoma of diffuse type in a young female patient aged 38. The patient was still asymptomatic at hospital admission, her only pathological sign being the finding of malignant cells of indeterminate origin at a routine Pap-test examination. Subsequent investigations showed the presence of a poorly differentiated gastric carcinoma, with metastatic diffusion to uterus, ovaries and peritoneum. Only a few cases of gastric carcinomas without cervical localization, detected by Pap-test, are reported in literature. A few other cases with cervical localization have been described. The aim of this work is to point out that a Pap-test smear may reveal the presence of extragenital tumors still unappreciated.

Objective: The aim of this study was to evaluate the usefulness of RF interstitial thermal ablation for treating hepatic cancer., Subjects and Methods: Fifty patients, 39 who had 41 hepatocellular carcinoma nodules and 11 who had 13 hepatic metastatic nodules, underwent RF interstitial thermal ablation. In all but one, a thermal necrosis volume greater than the tumoral nodule volume was created to obtain total tumor destruction. One large tumor was treated for debulking purposes., Results: Hepatocellular carcinoma nodule destruction was achieved in a mean of 3.3 sessions of RF interstitial thermal ablation. During a mean follow-up of 22.6 months (range, 3-66 months), 16 (41%) of 39 patients had recurrences; two (5%) of these patients showed local recurrences and the remaining 14 (36%) had new lesions. Nine of these 16 patients underwent further RF interstitial thermal ablation that proved effective. RF interstitial thermal ablation was also successfully repeated in four patients who had a second recurrence. With RF interstitial thermal ablation, we treated 54 hepatocellular carcinoma nodules in 39 patients. Eleven (28%) of the 39 patients died: five from hepatic failure due to advanced cancer and six from causes other than cancer. Autopsy was performed on three patients who died from causes other than cancer, one had had two new courses of RF interstitial thermal ablation for two new lesions. Gross examination failed to detect two treated tumor nodules; histologic examination of three other treated tumor nodules showed total necrosis in two nodules and a 3-mm focus of viable cancer cells in the other nodule. Cumulative survival curves showed the median survival time to be 44 months. The survival rate for the first year was 0.94, 0.86 for the second year, 0.68 for the third year, and 0.40 for the fourth and fifth years. In the patients treated for metastatic nodules, posttreatment imaging studies showed necrosis that varied from 80% to 100% in all cases. Pathologic studies performed on two patients who underwent surgery after RF interstitial thermal ablation showed 100% necrosis in one case and 80% necrosis in the other., Conclusion: RF interstitial thermal ablation is a useful percutaneous treatment for hepatic cancer.

An unusual case of multiple relapsing Spitz nevus (SN) in a patient with pseudohypoparathyroidism is described. It arose initially as a single lesion, and recurred twice as multiple agminated lesions that maintained the same histological pattern as the original SN. Nevertheless, the clinical behavior led to a diagnosis of metastasis from malignant melanoma at another medical institution. This case emphasizes the need for relying on accurate histopathological criteria to distinguish SN from malignant melanoma if inappropriate and detrimental therapeutic procedures are to be avoided.

The second known case of sporotrichosis caused by Sporothrix schenckii var. luriei in a patient living in Piacenza, Italy is described. In the absence of cultures, the diagnosis was based on histologic studies. Stained tissue sections (Hematoxylin and eosin, & Gomori methenamine silver) revealed hyaline, large, thick walled tissue form cells that had divided by septation or a budding process. These forms, along with the striking "eyeglass" configuration of incompletely separated cells that were also present, are the diagnostic features of this apparently rare variety. The use of a fluorescent antibody reagent, specific for S. schenckii, confirmed the identity of the etiologic agent.