{'fraction_non_alphanumeric': 0.030837004405286344, 'fraction_numerical': 0.013006083490664988, 'mean_word_length': 5.540466392318244, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 1, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Asymptomatic subcutaneous cervical mass due to Actinomyces odontolyticus infection in a pyriform sinus fistula

A 2-year-old boy presented with a left-sided, anterior cervical subcutaneous mass. The patient had no remarkable family or past history and no other accompanying symptoms. T2-weighted magnetic resonance imaging of the mass at a previous hospital showed an apparently circumscribed mass (Fig. 1a). The patient was referred to Nagano Children’s Hospital with suspected malignant disease. On admission, the mass was hard and minimally mobile. The patient reported no burning sensation or tenderness. Oral hygiene was good. Laboratory results were as follows: white blood cell count, 11.0 9 10/L; C-reactive protein, 0.05 mg/dL; and erythrocyte sedimentation rate, 20 mm/h. Five days after admission, biopsy of the cervical subcutaneous mass was performed under general anesthesia, after which a course of sulbactam/ampicillin was initiated because an infection was suspected on the basis of intraoperative rapid diagnosis. On the final pathology, although a large number of neutrophils were observed, monoclonal cell proliferation was not detected. Moreover, because sulfur granules (druse) were observed in a single field of one specimen (Fig. 1c), Actinomyces infection was suspected. Therefore, the biopsy specimen was analyzed for 16S rRNA gene amplification and sequencing using Actinomyces-specific primers. The final diagnosis was Actinomyces odontolyticus infection. Although the routine bacterial culture did not show Actinomyces infection, co-growth of a-Streptococcus and Eikenella corrodens was observed. Although the detected bacteria are oral inhabitants, there was no evidence of gingival disease, oral trauma, dental caries, or extraction. Symptoms improved with antibiotic treatment, and the patient was discharged 14 days after admission. He continued oral antibiotics therapy with amoxicillin/clavulanate for 6 months, and the symptoms completely resolved. At a later date, barium esophagography showed a pyriform sinus fistula (PSF) in the area of the subcutaneous abscess (Fig. 1b). Actinomyces is a Gram-positive facultative anaerobe and an endogenous flora of the oral cavity. Actinomyces infection, particularly cervicofacial actinomycosis, is rare in children. On the basis of a previous review of 17 pediatric cervicofacial actinomycosis cases, clinical features include disease development at any age in children, a higher frequency in girls, and an association with pain and fever. Clinical diagnosis is reached on histopathological confirmation of typical sulfur granules, positive culture, and/or isolation of Actinomyces species. Although the most predominant organism was A. israelii, only one patient reported A. odontolyticus infection as the cause. Actinomycosis, however, remains a diagnostic challenge. Microbiological identification is often difficult because this organism grows slowly and, thus, careful anaerobic culturing is required. On microscopy the lesions have an outer zone of granulation, consisting of collagen fibers and fibroblasts, and a central purulent focus containing neutrophils that surround the sulfur granules. Diagnosis on radiology is difficult because the findings of actinomycosis are non-specific. Therefore, in clinical practice, lack of responsiveness to empirical antibiotic therapy, presentation of a chronic palpable mass, difficulty in establishing a microbiological diagnosis, and imaging showing a soft-tissue mass make differentiating this mass from a neoplasm, granulomatous disease, or other infectious disease at initial presentation difficult. Although sulfur granules were observed in the present case, which led to suspicion of Actinomyces infection, a diagnosis of A. odontolyticus is considered to be more difficult because granules are usually absent in A. odontolyticus. Therefore, 16S rRNA-specific polymerase chain reaction using specimen or colony extraction may be important for making a correct diagnosis in a shorter period. The clinical utilization of this approach may require further validation. Pyriform sinus fistula represents an anomaly of the opening of the third and fourth branchial pouches in the pyriform sinus. PSF is often found in association with suppurative thyroiditis, recurrent neck abscess, odynophagia, and, occasionally, dyspnea. One report indicated that Streptococcus mitis was most commonly associated with PSF in pediatric patients, whereas Klebsiella pneumoniae was most commonly Correspondence: Ryu Yanagisawa, MD PhD, Division of Blood Transfusion, Shinshu University Hospital, 3-1-1 Asahi, Matsumoto 390-8621, Japan. Email: ryu@shinshu-u.ac.jp Received 2 November 2016; revised 21 April 2017; accepted 1 May 2017. doi: 10.1111/ped.13321