Metastatic Tonsil Squamous Cell Carcinoma: An Important Consideration in the Differential Diagnosis of Malignant Basaloid Neoplasms in the Skin: Case Report and Review of the Literature.

ABSTRACT: Malignant basaloid neoplasms of the skin are frequent, and their accurate diagnosis holds paramount importance for treatment and prognosis. However, these neoplasms can present diagnostic challenges because of their extensive differential diagnosis, which encompasses cutaneous metastasis among many other possibilities. We present a case of a 74-year-old man with a history of p16-positive palatine tonsil squamous cell carcinoma (SCC) treated with surgery and adjuvant radiation with no prior evidence of recurrence who presented to the dermatologist with 2 chin papules. The initial histopathologic evaluation of these lesions showed poorly differentiated malignant basaloid neoplasms. Subsequently, these biopsies were compared with the previous biopsies from his tonsil and lymph node, which showed similar findings including positive p16 staining and positive molecular testing for human papillomavirus-16, confirming the diagnosis of cutaneous metastasis from his previously diagnosed human papillomavirus-related tonsil SCC. Additional imaging studies found metastases to internal organs including the brain, and he was started on chemotherapy, immunotherapy, and radiation therapy. Cutaneous metastases from tonsil SCC are exceedingly rare, and only 5 cases have been described. Furthermore, this is the first case confirming the presence of high-risk human papillomavirus by molecular studies within the cutaneous metastases. The presented case underscores the importance of recognizing this unusual manifestation of tonsil SCC metastatic to the skin along with a good clinical patient history, ensuring accurate and prompt diagnosis and treatment of this condition.

Proton pencil beam scanning radiotherapy in the postoperative treatment of p16 positive squamous cell tonsillar cancer - evaluation of toxicity and effectivity.

PURPOSE: Patients with p16 positive tonsillar cancer (p16 + TC) have an excellent prognosis and long-life expectancy. Deintensification of therapy is a prevalent topic of discussion. Proton radiotherapy is one way to reduce radiation exposure and thus reduce acute and late toxicity. The aim is to evaluate treatment outcomes and toxicity of postoperative treatment with intensity-modulated proton therapy (IMPT). METHODS: Between September 2013 and November 2021, 47 patients with p16 + TC were treated postoperatively with IMPT. Median age was 54.9 (38.2-74.9) years, 31 were males and 16 were females. All patients had squamous cell carcinoma and underwent surgery as a primary treatment. Median dose of radiotherapy was 66 GyE in 33 fractions. Bilateral neck irradiation was used in 39 patients and unilateral in 8. Concomitant chemotherapy was applied in 24 patients. RESULTS: Median follow-up time was 4.2 (0.15-9.64) years. Five-year overall survival, relapse free survival and local control were 95.7%, 97.8% and 100%. The most common acute toxicities were dermatitis and mucositis, with grade 2 + in 61.7% and 70.2% of patients. No acute percutaneous gastrostomy insertion was necessary and intravenous rehydration was used in 12.8% of patients. The most common late toxicity was grade 1 xerostomia in 70.2% of patients and grade 2 in 10.6% of patients. Subcutaneous fibrosis of grades 2 and 3 occurred in 17.0% and 2.1% of patients, respectively. One patient developed late severe dysphagia and became PEG-dependent. CONCLUSION: IMPT for the postoperative treatment of p16 + TC is feasible with excellent efficiency and acceptable acute and late toxicity.

[Analysis on the ultrasonic characteristics of tonsillar lymphoma].

Objective: To analyze the ultrasonic features of tonsillar lymphoma to improve the diagnostic accuracy. Methods: The clinical, pathological and ultrasonic data of nine patients with tonsillar lymphoma confirmed by pathology at Tianjin Medical University Cancer Institute and Hospital during June 2015 and June 2022 were analyzed retrospectively, and the characteristics of their ultrasonic images were summarized. Results: All 9 cases of tonsil lymphoma were unilateral tonsil disease, including 4 cases on the left side and 5 cases on the right side. The average maximum diameter of tonsil lymphoma in 9 cases was 4.32 cm. There were 3 cases with simultaneous involvement of tonsil and cervical lymph nodes, all of which were ipsilateral lymph nodes. Gray scale ultrasound showed that the lesions were hypoechoic, with clear boundaries in 7 cases and unclear boundaries in 2 cases. The shape was full and irregular in 5 cases and oval in 4 cases. The echo was uniform in 7 cases and uneven in 2 cases. Color Doppler ultrasonography showed abundant internal blood flow signal in 1 case, a little dotted linear internal blood flow signal in 5 cases, and no obvious internal blood flow signal in 3 cases. Conclusions: The ultrasonic features of tonsillar lymphoma include hypoechoic area, clear boundary, full shape, irregular and uniform internal echo, no or low linear signal of internal blood flow. Ultrasonography is of great value in the diagnosis of this disease and can help clinical decision-making.

Extranodal natural killer/T-cell lymphoma with tonsil involvement: a case report.

BACKGROUND: Extranodal natural killer/T-cell lymphoma (ENKTL) with tonsil involvement is not common, especially in children. CASE PRESENTATION: A 13-year-old girl presented with an unexplained sore throat for more than 2 months, together with intermittent fever and suppurative tonsilitis. Nasopharyngoscopy revealed a pharyngeal mass. Enhanced computed tomography (CT) scan showed tonsillar hypertrophy and punctate calcification. Chronic pyogenic granulomatous inflammation with pseudoepithelial squamous epithelial hyperplasia was observed in left tonsil, and pyogenic granulomatous inflammation and a small number of T-lymphoid cells were detected in the right tonsil. The immunohistochemical results showed CD2+, CD3+, CD4+, CD5+, CD8+, granzyme B+, and TIA-1+. The Ki-67 proliferation index was 20%. The case showed T cell receptor gene rearrangement. Finally, the case was diagnosed as ENKTL of stage II with tonsil involvement. The patient received 6 cycles of chemotherapy with SMILE regimen, and showed complete response with no recurrence in the follow-up. CONCLUSION: We presented a rare case of ENKTL with tonsil involvement in a child. The patient showed complete response to the SMILE chemotherapy with no recurrence.

A Submucosal Tumor-like Lesion of the Cervical Esophagus Similar to the Tonsillar Structures of Waldeyer's Ring: A Case Report.

Esophageal submucosal tumors are rare, but their pathological types are diverse. In addition to the relatively common leiomyomas, some rare submucosal lesions are occasionally reported. Waldeyer's ring is described as a unique subtype of mucosa-associated lymphoid tissue, located in the naso-oropharynx. Studies have reported that Waldeyer's ring is the most common site of primary extranodal lymphoma in the head and neck. Interestingly, we encountered an esophageal submucosal tumor-like lesion similar to the tonsillar structures of Waldeyer's ring. A 38-year-old man underwent esophagoscopy after experiencing swallowing discomfort for 3 months. A protruding submucosal mass with slightly rough mucosa was found at the cervical esophagus approximately 20 cm from the incisors. Considering the possibility of the coexistence of a submucosal tumor and a mucosal lesion, as well as the continuous symptoms of swallowing discomfort, the patient underwent endoscopic submucosal dissection. The lesion was removed en bloc. However, histology revealed a lesion similar to the tonsillar structure of Waldeyer's ring between the lamina propria and submucosa. The patient was followed up for 6 months without recurrence or complaints. We report a new submucosal lesion and discuss its origin and treatment. Diagnostic ESD might be an effective option until its malignant potential is clarified.

Epidermotropic metastasis of squamous cell carcinoma of the tonsil: A case report with molecular confirmation.

Metastasis of oropharyngeal squamous cell carcinoma (SCC) to skin is uncommon and portends a poor prognosis. Clinical history and histopathology are key to discerning between metastatic disease vs de novo SCC of the skin. We describe a case of an HPV+ tonsillar SCC in a 77-year-old male, with metastasis to the neck skin. This case is unique because of prominent in situ epidermal involvement on skin biopsy specimen, complicating the distinction between primary and secondary disease. The nature of the lesion was resolved using next-generation sequencing of both the primary oropharyngeal SCC and skin lesion biopsy specimens. Both tumors showed identical ATR D1639G somatic mutations, while the skin lesion contained an additional POLE F1366L mutation. Clonal evolution of metastatic lesions is a well-described phenomenon; comparing the genetic profiles of primary and metastatic specimens can be useful in evaluating the tumor origin as well as identifying targetable genetic aberrations.

Prevalence and prognosis of synchronous distant metastatic tonsil squamous cell carcinomas.

BACKGROUND: To analyze the prevalence proportions and prognostic factors of synchronous distant metastases in patients with tonsil squamous cell carcinomas (TSCC). METHODS: TSCC patients were extracted from the Surveillance, Epidemiology and End Results (SEER) database between 2010 and 2014. We examined the association between clinical manifestations and distant metastases using Chi-squared tests. Predictors of 5-year survival were assessed using univariate and multivariate analyses. RESULTS: A total of 6193 patients were analyzed and lung was the most common site of distant metastases. Poorly/undifferentiated differentiation was found to be significantly correlated with lung metastasis (p=0.033) and liver and bone metastases were associated with African American (p=0.000 and p=0.000, respectively). A higher T classification was associated with higher prevalence of lung, liver, bone and brain metastasis (p=0.000, p=0.000, p=0.000 and p=0.007, respectively). The same results were found in N classification in lung, liver, and bone metastasis (p=0.000, p=0.000, and p=0.000, respectively). Worse prognosis was associated with older age, Blacks, lower grade, higher T and N classification, no surgery therapy and more metastatic sites. CONCLUSION: Lung was the most frequent lesion of synchronous distant metastases and liver and bone metastases were associated with African American. Higher T and N classification were independent prognostic parameters for higher prevalence of lung, bone, liver and brain metastasis. Worse prognosis was associated with older age, African Americans, lower grade, higher T and N classification, no surgery therapy and more metastatic sites.

Establishment and Validation of a Nomogram for Tonsil Squamous Cell Carcinoma: A Retrospective Study Based on the SEER Database.

This study aimed to establish and validate a comprehensive nomogram for predicting the cause-specific survival (CSS) probability in tonsillar squamous cell carcinoma (TSCC). We screened and extracted data from the SEER (Surveillance, Epidemiology, and End Results) database for the period 2004 to 2016. We randomly divided the 7243 identified patients into a training cohort (70%) for constructing the model and a validation cohort (30%) for evaluating the model using R software. Multivariate Cox stepwise regression was used to select predictive variables. The concordance index (C-index), the area under the time-dependent receiver operating characteristics curve (AUC), the net reclassification improvement (NRI), the integrated discrimination improvement (IDI), calibration plotting, and decision-curve analysis (DCA) were used to evaluate the model. The multivariate Cox stepwise regression analysis successfully established a nomogram for the 1-, 3-, and 5-year CSS probabilities for TSCC patients. The C-index, AUC, NRI, and IDI were all showed that the model has good discrimination. The calibration plots were very close to the standard lines, indicating that the model has a good degree of calibration, and the DCA curve further illustrated that the model has good clinical validity. We have established the first nomogram for predicting the 1-, 3-, and 5-year CSS probabilities for TSCC based on a large retrospective sample. Our rigorous validation and evaluation indicated that the model can provide useful guidance to clinical workers making clinical decisions about individual patients.

Comparative cost of transoral robotic surgery and radiotherapy (IMRT) in early stage tonsil cancer.

PURPOSE: To compare treatment costs and cost-effectiveness for transoral robotic surgery (TORS) and definitive intensity-modulated radiotherapy (IMRT) in managing early stage tonsil cancer. MATERIALS AND METHODS: Direct treatment costs for surgery and IMRT were calculated from SEER-Medicare data for a cohort with clinically early stage (cT1/2N0) p16+ tonsillar squamous cell carcinoma from Kaiser Permanente Southern California Health Plan between 2012 and 2017. A Markov decision tree model with a 5-year time horizon was then applied to the cohort which incorporated costs associated with treatment, surveillance, and recurrence. RESULTS: IMRT cost up to $19,000 more (35%) than TORS in direct treatment costs. When input into the Markov model, TORS dominated IMRT with lower cost and better effectiveness over a range of values. CONCLUSION: TORS is a more cost-effective treatment method than IMRT in early stage (cT1/2N0) tonsil cancer.

Radical Tonsillectomy and Superior Pharyngeal Constrictor Anatomy: A Cadaveric and Oncologic Specimen Assessment.

INTRODUCTION: The rise in primary surgical management of oropharyngeal squamous cell carcinoma has led to varying interpretations of the histopathologic evaluation following a radical tonsillectomy. The oncologic margin may be significantly influenced by the morphologic relations and anatomic dimensions of the palatine tonsil and superior pharyngeal constrictor (SPC) muscle. OBJECTIVE: The aim of this study was to characterize the gross and histologic anatomic features of the palatine tonsil and SPC muscle following an en bloc radical tonsillectomy. METHODS: Radical tonsillectomy specimens were collected from cadaveric and oncologic subjects. Specimens were processed using standard histopathologic techniques and were analyzed by a board-certified head and neck pathologist. The thickness of the SPC muscle and relationship to the tonsillar carcinoma were assessed. RESULTS: Six cadaveric and 10 oncologic specimens were analyzed. The mean minimum SPC width for all cadaveric specimens was 1.02 ± 0.50 mm. The mean minimum width for oncologic specimens was 0.76 ± 0.46 mm. The mean distance from tonsil carcinoma to the lateral specimen margin was 1.79 ± 1.39 mm. CONCLUSION: Due to the limited width of the SPC muscle, a margin in excess of 2 mm may not be attainable in a transoral radical tonsillectomy. Margin status may be ideally determined by the integrity of the SPC muscle in future oncologic studies, rather than an adequate distance measurement.

Lacrimal sac primary squamous cell carcinoma with synchronous tonsillar primary squamous cell carcinoma.

A gentleman with recurrent epiphora after two failed endonasal dacryocystorhinostomies was found to have a squamous cell carcinoma of the lacrimal sac at his third operation via an external approach. CT showed contralateral nodal involvement; however, biopsy of the node found it to be histologically distinct from the lacrimal sac lesion. A PET-CT revealed a second primary lesion located at the contralateral palatine tonsil. We discuss the histological features of squamous cell carcinomas and the impact on prognosis. This case highlights the importance of nasoendoscopy prior to lacrimal surgery. There should be a low threshold for lacrimal sac biopsy, and any anatomical or histological inconsistency should prompt further investigation.

Spontaneous hematoma of the thigh associated with antiproteinase-3 antibody in a patient with metastatic squamous cell carcinoma treated with nivolumab.

We report an unusual case of spontaneous intramuscular hematoma associated with antiproteinase 3 antibody in a patient with metastatic squamous cell carcinoma receiving nivolumab and the medical literature is reviewed.

Transoral Robotic Surgery With Transoral Retropharyngeal Lymph Node Dissection in Patients With Tonsillar Cancer: Anatomical Points, Surgical Techniques, and Clinical Usefulness.

OBJECTIVE: The purpose of this study was to evaluate the clinical usefulness of TORS and transoral robotic retropharyngeal lymph node (RPLN) dissection in tonsillar cancer patients with suspicious RPLN metastasis. METHODS: From April 2008 to March 2014, 71 patients with tonsillar cancer underwent transoral robotic surgery and standard neck dissection at the Yonsei Head and Neck Cancer Center. RESULTS: Three patients underwent transoral robotic ropharyngectomy with transoral robotic RPLN dissection because of suspicious RPLN metastasis. The mean age of the patients was 42 years (range, 31-50 years). There were no cases of wound infection or serious complications related to wound healing. Mild nasal regurgitation was observed during an oral diet immediately after surgery, but all patients spontaneously resolved without surgical treatment. There was no significant bleeding due to great vessel injury during surgery or swallowing difficulty due to cranial nerve IX injury. CONCLUSION: Although the oncologic stability and usefulness of this technique should be confirmed based on large-scale research, RPLN can be easily accessed and resected through our approach with less morbidity compared to the conventional surgical approach. In addition, because RPLN metastasis can be performed pathologically based on obtained specimens, it will be helpful to explore whether to perform adjuvant radiation.

Treponema denticola chymotrypsin-like proteinase may contribute to orodigestive carcinogenesis through immunomodulation.

BACKGROUND: Periodontal pathogens have been linked to oral and gastrointestinal (orodigestive) carcinogenesis. However, the exact mechanisms remain unknown. Treponema denticola (Td) is associated with severe periodontitis, a chronic inflammatory disease leading to tooth loss. The anaerobic spirochete Td is an invasive bacteria due to its major virulence factor chymotrypsin-like proteinase. Here we aimed to investigate the presence of Td chymotrypsin-like proteinase (Td-CTLP) in major orodigestive tumours and to elucidate potential mechanisms for Td to contribute to carcinogenesis. METHODS: The presence of Td-CTLP within orodigestive tumour tissues was examined using immunohistochemistry. Oral, tonsillar, and oesophageal squamous cell carcinomas, alongside gastric, pancreatic, and colon adenocarcinomas were stained with a Td-CTLP-specific antibody. Gingival tissue from periodontitis patients served as positive controls. SDS-PAGE and immunoblot were used to analyse the immumodulatory activity of Td-CTLP in vitro. RESULTS: Td-CTLP was present in majority of orodigestive tumour samples. Td-CTLP was found to convert pro MMP-8 and -9 into their active forms. In addition, Td-CTLP was able to degrade the proteinase inhibitors TIMP-1, TIMP-2, and α-1-antichymotrypsin, as well as complement C1q. CONCLUSIONS: Because of its presence within tumours and regulatory activity on proteins critical for the regulation of tumour microenvironment and inflammation, the Td-CTLP may contribute to orodigestive carcinogenesis.

Pediatric Tonsil Cancer: A National and Institutional Perspective.

OBJECTIVE: To evaluate childhood and adolescent tonsil cancer incidence and to identify the clinical characteristics indicative of those patients who would benefit from urgent operative intervention. STUDY DESIGN: The Surveillance, Epidemiology and End Results 18 database, inclusive of national cancer statistics from 1973 to 2013, provided quantitative tonsil cancer incidence data. An institutional retrospective chart review of pediatric patients diagnosed with tonsil malignancy from January 2013 to January 2017 identified supplementary qualitative clinical presentation information. RESULTS: The Surveillance, Epidemiology and End Results 18 database included 138 pediatric patients with tonsil cancer with an age-adjusted incidence rate of 0.021/100 000 patients per year. The majority of cases were unilateral (79.7%), and there was both a male and Caucasian predominance. Non-Hodgkin lymphoma (84.1%) was the most common malignancy, of which Burkitt lymphoma (31.1%), diffuse large B-cell lymphoma (26.8%), and follicular lymphoma (10.1%) were the most common subtypes. Five tonsillar malignancy patients were identified upon institutional chart review. The majority likewise had non-Hodgkin lymphoma and all shared a history of rapid tonsillar enlargement over ≤12 weeks. Significant tonsillar asymmetry was present in 4 patients. Four patients additionally exhibited prominent cervical lymphadenopathy. CONCLUSIONS: Pediatric tonsil cancer is rare, with non-Hodgkin lymphoma accounting for the majority of pediatric tonsillar malignancies. A high index of suspicion is appropriate in children who present with relatively rapid tonsil enlargement, tonsillar asymmetry characterized by a difference in tonsillar size of ≥2 degrees on the Brodsky scale, or concurrent prominent cervical lymphadenopathy.

Mucosal and skin HPV types in tumour-free tonsils and tonsillar tumours.

Human papillomavirus (HPV) infection is associated with tonsillar cancer (TC) whose incidence in humans is increasing. Tonsillar tumours are not ordinarily preceded by clinically apparent precancerous lesions, and no markers of the early stage disease are available. Therefore, we evaluated the presence of an active HPV infection also in tumour-free tonsillar tissue. Formalin-fixed paraffin-embedded (FFPE) tonsillar specimens from 114 patients with TC and 114 age and gender matched controls were screened for the presence of HPV DNA, expression of HR-HPV E6 mRNA, and p16 overexpression. HPV DNA was identified in 3.5% of tumour-free tissues, HR-HPV16 and 58 and LR-HPV111 and 17 were each detected in a single sample. No HR HPV E6 mRNA and p16 overexpression was found. The prevalence of HPV DNA in TC was 69.3%, with HPV16 being the most common (94.9%). Eighty-four percent of HPV16-positive tumours expressed HR HPV E6 mRNA, while no E6 mRNA was present in samples positive for HPV52 and 58. The overexpression of p16 correlated well with HPV DNA in TC, but in tumour-free tonsils no overexpression of p16 was detected.Our data provide further evidence of the etiological role of HPV16 in TC. In tumour-free tissue, the presence of HR-HPVs was rare and silent, as shown by direct and indirect markers.

Atypical Metastasis of p16-Positive Tonsillar Squamous Cell Carcinoma to the Pleura: A Case Report.

Incidence rates and patterns of distant metastases of head and neck malignancies are well documented in the literature, such that focused management strategies are routinely practiced in anticipation of their likely behavior. Head and neck tumors are known to most commonly metastasize to the lungs, skeletal system, and liver, generally within 2 years of definitive treatment and in the context of poor locoregional control of the primary lesion. Recent studies, however, have shown that human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma (SCCa) tumors display different patterns of distant metastases than those traditionally described for head and neck HPV-negative SCCa tumors. This finding has substantial implications for how patients undergoing treatment of these cancers should be surveilled after therapy. This report describes a case of p16-positive tonsillar SCCa with metastasis to a highly unusual secondary site in the pleura to show an example of the unconventional patterns of distant metastases reported for HPV-positive oropharyngeal SCCa in the recent literature. We aim to provide a more thorough understanding of this case by discussing the pathogenesis of metastatic spread to the pleura and the clinical progression generally observed in patients with secondary pleural malignancy. This report goes on to investigate how behaviors of distant metastases exhibited by HPV-positive oropharyngeal SCCa differ from those of more conventionally described head and neck HPV-negative SCCa and the implications thereof for strategies of post-treatment surveillance of these tumors going forward.

The incidence of malignancy in clinically benign cystic lesions of the lateral neck: our experience and proposed diagnostic algorithm.

AIM: Solitary cystic masses of the lateral neck in an adult patient can pose a diagnostic dilemma. Malignancy must be ruled out since metastases arising from H&N cancers may mimic the presentation of benign cystic masses. Only a small number of studies have investigated the diagnostic management and malignancy rate of clinically benign solitary cervical cystic lesions. There are no established guidelines for the diagnostic evaluation. METHODS: Retrospective review of the clinical, cytological, radiological, and pathological records of all adult patients (> 18 years) operated on for second branchial cleft cysts (BrCC) between 1/2008-2010/2016. Patients with apparent primary H&N malignancy, history of H&N cancer or irradiation, preoperative fine needle aspiration (FNA) of highly suggestive or confirmed malignancy, missing pertinent data, or age less than 18 years were excluded from analysis. RESULTS: 28 patients were diagnosed as having BrCC. The diagnosis was based on clinical findings, FNA cytology, and typical sonographic features. The histologic analysis determined an overall rate of malignancy of 10.7% (3/28): two patients had metastatic papillary thyroid carcinoma, and one patient had metastatic tonsillar squamous cell carcinoma. Purely cystic features on pre-operative ultrasound was the only significant predictor for true BrCC on final histology (p = .02). CONCLUSIONS: Occult malignancy is not rare among adult patients presenting with a solitary cystic mass of the lateral neck. A diagnostic algorithm is proposed. Further studies are needed to establish the appropriate workup and management of an adult patient presenting with a solitary cystic mass of the lateral neck.

Computed tomographic appearance of canine tonsillar neoplasia: 14 cases.

The palatine tonsil is an uncommon site of oral canine neoplasia. For affected tonsils, squamous cell carcinoma is the most frequent type of neoplasia, followed by melanoma and lymphoma. Computed tomography (CT) is increasingly used for investigation of canine oropharyngeal pathology; however, limited information is available on the CT appearance of tonsillar neoplasms. Objectives of this retrospective descriptive case series were to characterize the CT features of canine tonsillar neoplasia and determine whether specific CT features differentiate nonneoplastic from neoplastic tonsils. Computed tomographic studies of 14 dogs diagnosed with tonsillar neoplasia were retrieved from two referral hospitals and reviewed by two observers. Diagnosis was based on histology or cytology. Carcinoma was diagnosed in 11 dogs, melanoma in two and lymphoma in one dog. Specific CT features of the tonsil and regional lymph nodes did not differentiate neoplastic from nonneoplastic tonsillar diseases, but regional lymph node CT features were useful for diagnosis in some cases. Marked enlargement (width ≥ 18 mm, 12/18), heterogeneity (16/18), and loss of the hypoattenuating hilus (18/18) of the medial retropharyngeal lymph node were common concomitant features of tonsillar neoplasia. The medial retropharyngeal and mandibular lymphadenomegaly was ipsilateral to the neoplastic tonsil in 8/12 and 6/9 dogs, respectively. Five dogs demonstrated little or no enlargement of the tonsil despite the associated metastatic lymphadenomegaly. Tonsillar neoplasia should therefore be considered as a differential diagnosis for dogs with CT evidence of isolated medial retropharyngeal lymphadenomegaly (regardless of normally sized tonsils), or of any enlarged tonsil with no associated lymphadenomegaly.