Pyoderma gangrenosum (PG) is a rare, non-infectious neutrophilic dermatosis with painful ulcers. It mainly occurs in adult females, however it can affect children. Although it commonly involves the lower extremities, any cutaneous site may be affected. However, involvement of the oral mucosa is very rare. The mode of onset and progression of skin lesions is acute and rapid. Treatments for this condition include pain control, local skin care, and systemic administration of immunomodulators.

　We describe an 8-year-old girl who was transferred to our medical center because of severe ulcers over the entire body, including the lips and gingiva, for 3 weeks. She had no past medical history, and blood tests did not show any specific findings. The histopathological findings with skin biopsy showed non-specific necrotic tissues and infiltration of inflammatory cells. By excluding other possibilities, we diagnosed PG. Treatment with high-dose systemic corticosteroids followed by cyclosporine and infliximab was effective. After treatment began, oral lesions as well as other cutaneous lesions resolved at the same pace. The ulcers healed, and the patient was discharged 3 months after starting treatment.

Plasmablastic lymphoma (PBL) was first reported in 1997 as a non-Hodgkin’s lymphoma with a poor prognosis that occurred in the oral cavity of some human immunodeficiency virus (HIV) -positive patients. In 2008, it was added to the WHO classification as a type of aggressive B-cell lymphoma that can also occur in extranodal sites of elderly or immunocompromised patients. As half of the cases are related to Epstein-Barr virus (EBV) infection and categorized as EBV-associated lymphoproliferative disorders. We report a case of EBV-positive PBL that occurred in the mandibular gingiva of an HIV-negative patient. The patient was an 87-year-old man with a mass in the gingiva surrounding the second left mandibular molar. A biopsy revealed that the lesion was EBV-positive PBL. Serologically, HIV antibody was negative. The patient underwent radiation therapy (50 Gy), which led to a completely positive response. After treatment, no recurrence was detected. Three years one month after treatment, dehydration led to a decrease in the level of consciousness and the resulting deterioration of general condition, and the patient died one month later.

Congenital factor V deficiency is a congenital bleeding disorder, and its frequency is estimated to be 1 per million population. There has been no report regarding the treatment of oral cancer accompanied by congenital factor V deficiency. In this report, we describe the perioperative management of factor V activity in a tongue cancer patient with congenital factor V deficiency. A 68-year-old woman who had congenital factor V deficiency was referred to our hospital because of an ulcer at the left edge of her tongue. A histopathological examination led to a diagnosis of oral squamous cell carcinoma. Preoperative screening examinations revealed prolonged prothrombin time (PT) and activated partial thromboplastin time (APTT). The factor V activity was 11%. After the preoperative transfusion of 6 units of fresh frozen plasma (FFP), factor V activity was corrected to 30% from 12%, and the patient underwent partial glossectomy functional neck dissection, and tracheotomy under general anesthesia. To perioperatively maintain the factor V activity over 30%, 38 units of FFP were given during 4 days after surgery, and no hemorrhagic complications were observed. At 4 years 2 months after the operation, there has been no sign of recurrence or lymph node metastasis.

Epithelial-myoepithelial carcinoma (EMC) is a rare low-grade malignant salivary gland neoplasm that accounts for less than 1% of all salivary gland neoplasms and most commonly occurs in the parotid gland. We report a case of primary epithelial-myoepithelial carcinoma of the left hard palate. The patient was a 76-year-old woman who was referred to our hospital because of a painless mass in the left hard palate. T2-weighted magnetic resonance (MR) imaging revealed a clearly demarcated, somewhat heterogeneous, hyperintense tumor with partially irregular margins. Because the preoperative histological examination revealed that the salivary gland tumor might be malignant, surgical resection of the malignant palatal tumor was performed with the patient under general anesthesia. In the resected tissue, the tumor was composed of multilobular proliferations of biphasic tubules of inner eosinophilic cells and outer clear cells. Immunohistochemical examination revealed that the outer layer consisted of clear myoepithelial cells positive for S-100 protein (S-100), vimentin, α-smooth muscle actin (α-SMA), and glial fibrillary acidic protein (GFAP), and the inner layer consisted of duct-forming epithelial cells positive for pan-cytokeratin (AE1/AE3). On the basis of these results, EMC was diagnosed. No signs of recurrence or distant metastasis have been seen as of 4 years postoperatively, and the progress of the patient has been satisfactory.

Cystadenocarcinoma is one example of a rare salivary gland tumor, and the most common its location is the parotid gland. We report a case of cystadenocarcinoma arising in the apex of the tongue. The patient was a 53-year-old woman who was referred to our hospital for evaluation of a tumor of the tongue. The lesion was well-circumscribed, elastic hard, and painless; it was 14 mm in diameter and arose in the apex of the tongue. After a biopsy specimen was obtained and analyzed, adenocarcinoma was diagnosed. Under general anesthesia, partial resection of the tongue was performed. The histopathological diagnosis was cystadenocarcinoma, showing large and small cystic tumors that featured papillary proliferations of cuboidal to columnar neoplastic cells with mucus production. The tumor had proliferated into the surrounding tissue. There was no recurrence or metastasis during the 4 years and 2 months of postoperative follow-up.

Nasoalveolar cysts account for 2.5% of all non-odontogenic cysts and are often found in adults. We describe our experience with a nasoalveolar cyst in a young patient, a 7-year-old girl, who had consulted her local dentist after noticing swelling in the right nasal alar region approximately 2 months before consulting our department. After no lesion had been initially detected on panoramic radiography, the girl visited our department and requested in-depth examination and treatment. Computed tomography (CT) revealed a slight dish-shaped depression in the alveolar bone in contact with a lesion. T2-weighted magnetic resonance imaging showed a shadow with distinct margins and interior uniform high signal intensity, measuring approximately 18 × 14 × 12 mm and extending from the labio-alveolar region identified on computed tomography to the lower region of the right piriform aperture. Cystectomy was performed with the patient under general anesthesia based on a clinical diagnosis of a nasoalveolar cyst. The fluid of the cyst was liquid gray to pale yellow and slightly pus-like. Histopathological examination revealed a cyst enveloped in what appeared to be columnar epithelium or stratified squamous epithelium, and the histopathological diagnosis was a nasoalveolar cyst.

Desmoplastic fibroma is a benign fibrous tumor of bone, initially described by Jaffe in 1958. Although classified as benign, it frequently shows local aggressive behavior and has a high rate of recurrence. In this article, we report the spontaneous regression of suspected desmoplastic fibroma in the mandible, which showed recurrence and rapid growth after surgery. An 81-year-old woman visited our department with a chief complaint of swelling of the right buccal mucosa. Radiographic examination showed a lesion suspected to be a solid tumor in the right-side wisdom tooth apical region of the mandible. The lesion was removed by enucleation and curettage with the patient under general anesthesia, and the clinical diagnosis was an odontogenic tumor. Histopathologically, the mass was diagnosed as a suspected desmoplastic fibroma. Radiographic examination showed recurrence and rapid growth of the tumor in the 8^th month after surgery. We recommended an extended surgical operation, but she was observed without treatment at her strong request. She has been followed up for 30 months since surgery and the lesion size gradually became smaller. Although the mechanism and cause of the spontaneous regression is difficult to determine, further follow-up is necessary.

We present a case of extraosseous/peripheral type (PA) ameloblastoma. Histopathologically, the tumor was granular cell type. The patient was a 66-year-old man who presented with a 20 × 12 × 6 mm tumor on the gingiva of the lower left molar region. Alveolar bone absorption by the tumor was found on computed tomographic imaging. A biopsy was performed, and the histological diagnosis was granular cell type ameloblastoma. Based on the diagnosis of PA, the tumor was excised with peripheral osteotomy, performed with the patient under general anesthesia. Histopathologically, the tumor was continuous with the surface epithelium, and there were large round cells with acidophilic granular cytoplasm. No evidence of recurrence was found during 24 months of observation after surgery.

Acquired hemophilia A is a rare disease induced by acquisition of factor Ⅷ inhibitors. The reported incidence of the disease is 1.48 cases per million persons per year; it is characterized by sudden bleeding symptoms. We report a case of acquired hemophilia A in a patient with a submucosal hematoma of the tongue. An 88-year-old woman presented with fresh bleeding from her mouth that was associated with a tongue hematoma. The clot was removed, and a tongue laceration was revealed. The bleeding tongue mucosa was sutured, and hemostasis was achieved. However, the swelling of the tongue gradually increased, and the hematoma worsened. Given the potential for rapid airway obstruction, the patient was admitted to a unit with closely monitored beds. Coagulation screening revealed prolonged activated partial thromboplastin time. In addition, decreased factor Ⅷ coagulation activity and factor Ⅷ inhibitor expression were detected. Therefore, our patient was given a diagnosis of acquired hemophilia A. The patient successfully responded to treatment with recombinant activated factor Ⅶ, prednisolone, and cyclophosphamide, given to control the hemorrhage and inhibit the formation of autoantibodies against factor Ⅷ. On hospital day 25, a significant decrease in the inhibitor titer and increase in factor Ⅷ activity were observed. The patient was discharged and is currently being treated on an outpatient basis in our hospital. Although acquired hemophilia A is a rare coagulopathic condition, it should be included as a differential diagnosis in patients with sudden-onset severe hemorrhagic tendency of unknown origin.

An odontoma is an odontogenic tumor composed of enamel, dentine, and cementum and is usually less than 20 mm in diameter. The World Health Organization classification divides odontomas into complex and compound. In previous reports from Japanese institutions, only two cases of compound odontoma arising in the mandible and greater than 30 mm in diameter have been reported. We describe a large compound odontoma arising in the mandible of a child.

　A 6-year-old girl was referred to our hospital for evaluation of a radiopaque area on the left side of the mandible. Radiographic and computed tomographic examinations showed a large, circumscribed, radiopaque lesion, which measured 30 × 22 × 20 mm and was surrounded by a thin radiolucent area accompanied by an impacted tooth. Several small tooth-like structures were noted within the lesion. An odontoma was clinically diagnosed, and the tumor and impacted tooth were surgically removed by an intraoral approach with the patient under general anesthesia. The resected tumor was covered by a thin capsule and consisted of many small tooth-like structures. The histopathological diagnosis was a compound odontoma. The postoperative course was satisfactory, and we are continuing periodic follow-up examinations of the patient.

Sialolipoma, a new variant of lipoma, is a rare, benign tumor of the salivary glands that comprises both glandular tissue and mature fat cells. Here we describe the characteristic features of a sialolipoma of the retromolar triangle and review the literature.

　A 62-year-old woman presented with an elliptical tumor (diameter 5 mm) arising in the retromolar triangular mucosa. Panoramic X-ray images revealed the absence of bone resorption in the jawbone adjacent to the tumor, and magnetic resonance imaging could not confirm deeper progression. The pathological findings of a biopsy specimen obtained during resection performed with the patient under general anesthesia in September 2016 confirmed a diagnosis of sialolipoma.

　Sialolipoma arising from small salivary glands is very rare, and only three reports have described sialolipoma arising in the retromolar triangle in the domestic and international literature between 2001 and 2017. Our patient has remained free of lipoma recurrence for 18 months after surgical resection.

We report a rare case of a diverticulum-like lesion arising in the mandibular gingivobuccal fold. An 86-year-old man visited his primary care dental clinic to receive dental treatment. Oral examination revealed a pouch-like lesion in the right mandibular gingivobuccal fold. The patient denied any history of trauma or operation around the oral cavity and was not aware of the lesion until the dentist pointed it out. He was referred to our department for examination and treatment. On oral examination, the pouch-like lesion measured 6 mm in length and 5 mm in depth. We diagnosed a diverticulum-like lesion, and it was surgically resected with the patient under local anesthesia. The specimen had a smooth surface, and was elastic and soft. Histopathological examination revealed a cystic lesion lined by keratinized stratified squamous epithelium, and inflammatory cell infiltration was observed in the subepithelial layer. The epithelial lining of the cystic lesion was continuous with the buccal mucosa. Based on the clinicopathological findings, we finally diagnosed a diverticulum-like lesion.

Pseudogout is acute arthritis caused by calcium pyrophosphate dehydrate (CPPD). We report a case of pseudogout in the temporomandibular joint (TMJ) that was effectively diagnosed on Gram staining.

　A 79-year-old woman was referred to our hospital because of swelling and pain in a left temporomandibular lesion. Clinical and blood test findings suggested acute suppurative arthritis of the TMJ. The patient was treated with antibiotics after arthrocentesis. Bacteria was not detected on Gram staining of joint fluid, but crystal components were comfirmed. Pseudogout was diagnosed on the basis of multiple small regions of mineralization and imaging and crystal characteristics under a polarizing microscope. Symptoms were improved by nonsteroidal anti-inflammatory drugs (NSAIDs) after the cessation of antibiotics. Gram staining was a simple and quick technique that facilitated the diagnosis of temporomandibular pseudogout.

Localized herpes zoster is a disease with vesicular lesion formation in a circumscribed area of the body, caused by reactivation of varicella-zoster virus. The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is one of the causes of hyponatremia, an electrolyte abnormality that occurs when blood sodium level drops to less than 135 mEq/L, but reportedly, localized herpes zoster is rarely accompanied by SIADH.

　An 87-year-old woman with a diagnosis of herpes zoster of the third division of the left trigeminal nerve received intravenous acyclovir on an inpatient basis in our department. Despite an improvement in symptoms, the blood sodium level decreased to 114 mEq/L after intravenous infusions of acyclovir for 6 days. Test results confirmed a diagnosis of SIADH, and treatment with physiological saline and the restriction of fluid intake helped improve the blood sodium level.

　Our search for localized herpes zoster accompanied by SIADH resulted in 14 cases including the above one (average number of days until onset: 7.38 days, average blood sodium level at onset: 114.1 mEq/L). Treatment with physiological saline and the restriction of fluid intake were effective in all cases. It is important to confirm complications of SIADH by regularly testing blood sodium levels when localized herpes zoster is treated.