Transparency-enhancing technology allows the three-dimensional assessment of esophageal carcinoma obtained by endoscopic submucosal dissection

BACKGROUND

Although much progress has been made in diagnosis of carcinomas, no established methods have been confirmed to elucidate their morphological features.

METHODS

Three-dimensional structure of esophageal carcinomas was assessed using transparency-enhancing technology. Endoscopically resected esophageal squamous cell carcinoma was fluorescently stained, optically cleared using a transparency-enhancing reagent called LUCID, and visualized using laser scanning microscopy. The resulting microscope images were converted to virtual HE images for observation using ImageJ software.

RESULTS

Microscopic observation and image editing enabled three-dimensional image reconstruction and conversion to virtual HE images. The structure of abnormal blood vessels in esophageal carcinoma recognized by endoscopy could be observed in the 3 dimensions. Squamous cell carcinoma and normal squamous epithelium could be distinguished in the virtual HE images.

CONCLUSIONS

The results suggested that transparency-enhancing technology and virtual HE images may be feasible for clinical application and represent a novel histopathological method for evaluating endoscopically resected specimens.

Histopathological, Demographic, and Clinical Signatures of Medulla Oblongata Germ Cell Tumors: A Case Report With the Review of Literature

The medulla oblongata is one of the rarest sites of occurrence for germ cell tumors (GCTs) of the central nervous system. As there is scant data regarding epidemiology, clinical presentations, optimal intervention, and long-term prognosis, we aimed to delineate the features of this rare entity by presenting our representative case and performing a quantitative review of the literature. A 24-year-old woman presented to our department with vertigo and swallowing difficulties. Magnetic resonance imaging revealed a homogenously enhanced exophytic lesion arising from the medulla oblongata and extending to the fourth ventricle. Surgical resection was performed and a histological diagnosis of pure germinoma was made. The patient underwent chemotherapy and whole-ventricular irradiation. No recurrence has been experienced for 4 months after the surgery. According to the literature, the prognosis of GCTs at the medulla oblongata seems no worse than those at typical sites. Striking features including occurrence at an older age, female preponderance, and a predominance of germinoma were noteworthy. The pattern of local recurrence suggests extensive radiation coverage is not a prerequisite. Special attention is needed for cardiac and respiratory functions as the main factors eliciting mortality.

Myeloid sarcoma and pathological fracture: a case report and review of literature

Myeloid sarcoma is a rare clinical entity that presents as an isolated proliferation of leukemic cells, concurrently with or at relapse of acute myeloid leukemia (AML), myelodysplastic syndromes/neoplasms (MDS), chronic myeloid leukemia (CML), and myeloproliferative neoplasm (MPN). Myeloid sarcoma disrupts the normal architecture of its surrounding tissues. When it forms in long bones, it can cause their pathological fracture. We recently experienced a rare case of MDS presenting with myeloid sarcoma in the femur that eventually resulted in its pathological fracture. Detailed chromosomal analysis of the bone marrow cells suggested emergence of myeloid sarcoma during the fast-paced progression of MDS just after acquiring trisomy 22. A comprehensive review of previous cases of myeloid sarcoma-associated pathological fracture indicated possible involvement of structural rearrangements of chromosomes 9 and 22. Management of myeloid sarcoma should continue to improve, and clinicians should note that myeloid sarcoma with specific chromosomal alterations needs extra medical attention to prevent pathological fracture.

COVID-19 Analysis in Tissue Samples Acquired by Minimally Invasive Autopsy in Out-of-Hospital Deaths with Postmortem Degeneration

Minimally invasive autopsy (MIA) is an alternative to a full autopsy for the collection of tissue samples from patients' bodies using instruments such as a biopsy needle. MIA has been conducted in many cases of coronavirus disease 2019 (COVID-19) and has contributed to the elucidation of the disease pathogenesis. However, most cases analyzed are hospital deaths, and there are few reports on the application of MIA in out-of-hospital deaths with varying extents of post-mortem changes. In this study, MIA and autopsies were performed in 15 patients with COVID-19 2-30 days after death, including 11 out-of-hospital deaths. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genome detection by reverse transcriptase quantitative polymerase chain reaction using MIA samples was mostly consistent with autopsy samples, particularly lung tissue, even in out-of-hospital cases. MIA had high sensitivity and specificity (> 0.80). Histological examination of lung tissue obtained by MIA showed characteristics of COVID-19 pneumonia, with 91% agreement with autopsy samples, whereas localization of SARS-CoV-2 protein in lung tissue was indicated by immunohistochemistry, with 75% agreement. In conclusion, these results suggest that MIA is applicable to out-of-hospital deaths due to COVID-19 with various postmortem changes, especially when autopsies are not available.

Multimodal imaging findings of intrahepatic cholangiocarcinoma arising from a biliary adenofibroma: a case report with radiological-pathological correlation

PURPOSE

Biliary adenofibroma is a solid microcystic epithelial neoplasm in the liver, comprising microcystic and tubuloacinar glandular tissues lined by a non-mucin secreting biliary epithelium and supported by a fibrous stroma. It is an extremely rare benign tumor with potential for malignant transformation. Herein, we report the case of a 64-year-old woman diagnosed with intrahepatic cholangiocarcinoma arising from biliary adenofibroma.

METHODS

Imaging studies revealed a tumor of 50 mm diameter, consisting of two components in S1 of the liver. The ventral portion of the tumor showed an ill-defined mass with early peripheral and gradual centripetal enhancement invading to the middle hepatic vein on computed tomography (CT), diffusion restriction on magnetic resonance images, and high fluorine-18-2-deoxy-D-glucose (FDG) uptake on positron emission tomography, like conventional intrahepatic cholangiocarcinoma. The dorsal portion showed a well-defined and low-attenuated mass with heterogeneous early enhancement and partial wash-out on CT, marked hyperintensity on heavily T2-weighted images, and low FDG uptake. The patient subsequently underwent extended left hepatectomy.

RESULTS

Pathologically, the former was diagnosed as cholangiocarcinoma and the latter as biliary adenofibroma. We discuss the radiological-pathological correlation of the tumor with a literature review.

CONCLUSION

Preoperative diagnosis of biliary adenofibroma is extremely challenging; however, clinically, it is crucial not to miss the presence of malignant findings.

White epidermoid cyst transformation after stereotactic radiosurgery: illustrative case

BACKGROUND

White epidermoid cysts (WECs) are a rare type of epidermoid cyst with atypical radiological features. The epidemiological aspects and mechanisms of their onset remain unknown. Herein, the authors report a unique case of WEC transformation from a typical epidermoid cyst after stereotactic radiosurgery (SRS), confirmed by radiological and pathological findings.

OBSERVATIONS

The case involved a 78-year-old man with a history of 2 surgeries for a left cerebellopontine angle typical epidermoid cyst 23 years earlier and SRS using the CyberKnife for recurrent trigeminal neuralgia (TN) 14 years earlier. The tumor with high intensity on T1-weighted imaging, low intensity on T2-weighted imaging, without restriction on diffusion-weighted imaging had gradually enlarged after SRS. Therefore, a salvage surgery was performed via a left suboccipital craniotomy, and the intraoperative findings showed a cyst with a brown, viscous liquid component, consistent with those of WECs. Histopathologically, keratin calcification and hemorrhage were identified, leading to a diagnosis of WEC. The postoperative course was uneventful, and the TN resolved. No tumor recurrence was recorded at 2 years postoperatively.

LESSONS

To the best of the authors' knowledge, this is the first world case of WEC transformation from a typical epidermoid cyst after SRS, confirmed by radiological and pathological findings. Radiation effects could have been involved in this transformation.

A case of intravascular lymphoma presenting with a lesion in the splenium of the corpus callosum

Intravascular lymphoma (IVL) is difficult to diagnose because its clinical presentation and laboratory and imaging findings are nonspecific. Herein, we report a case of IVL presenting as a lesion in the splenium of the corpus callosum. A 52-year-old man attended the emergency department with a 2-week history of progressively worsening abnormal behavior and gait disturbance. Magnetic resonance imaging on admission revealed an oval lesion in the splenium of the corpus callosum. The follow-up magnetic resonance imaging performed 2 months after disease onset revealed multiple high-signal areas in the bilateral cerebral white matter on T2-weighted images and diffusion-weighted images. The blood test results showed an elevated level of lactate dehydrogenase and serum-soluble interleukin-2 receptor. These findings were compatible with the diagnosis of IVL. IVL is often difficult to diagnose due to a wide variety of clinical presentations and imaging findings.

High titers of infectious SARS-CoV-2 in corpses of patients with COVID-19

OBJECTIVES

The prolonged presence of infectious SARS-CoV-2 in deceased patients with COVID-19 has been reported. However, infectious virus titers have not been determined. Such information is important for public health, death investigation, and handling corpses. The aim of this study was to assess the level of SARS-CoV-2 infectivity in the corpses of patients with COVID-19.

METHODS

We collected 11 nasopharyngeal swabs and 19 lung tissue specimens from 11 autopsy cases with COVID-19 in 2021. We then investigated the viral genomic copy number by real-time reverse transcription-polymerase chain reaction and infectious titers by cell culture and virus isolation.

RESULTS

Infectious virus was present in six of 11 (55%) cases, four of 11 (36%) nasopharyngeal swabs, and nine of 19 (47%) lung specimens. The virus titers ranged from 6.00E + 01 plaque-forming units/ml to 2.09E + 06 plaque-forming units/g. In all cases in which an infectious virus was found, the time from death to discovery was within 1 day and the longest postmortem interval was 13 days.

CONCLUSION

The corpses of patients with COVID-19 may have high titers of infectious virus after a long postmortem interval (up to 13 days). Therefore, appropriate infection control measures must be taken when handling corpses.

A case of right hypodysplastic kidney and ectopic ureter associated with bicornuate uterus in a prepubertal girl

Congenital anomalies of the kidney and urinary tract (CAKUT) are frequently associated with Mullerian anomalies. This can be explained by the fact that Mullerian duct elongation depends on the preformed Wolffian duct during embryogenesis. While CAKUT such as unilateral renal agenesis and multicystic dysplastic kidney are commonly identified prenatally by routine ultrasound, the diagnosis of Mullerian anomalies is often delayed, increasing the risk of complications such as endometriosis or pelvic inflammatory disease. Herein, we report a case of a premenarchal girl who had initially been diagnosed with right multicystic dysplastic kidney. She presented with continuous urinary incontinence at 4 years old and further evaluation by contrast-enhanced computed tomography, cystoscopy, colposcopy, ureterography, and hysterosalpingography led to the final diagnosis of right hypodysplastic kidney and ectopic ureter associated with bicornuate uterus. A strong family history of uterine malformations prompted the examination of the uterus. Genetic testing was suggested but the family declined. She is planned to be referred to a gynecologist at puberty for further assessment. The recognition and screening rate of concurrent Mullerian anomalies in CAKUT patients varies between institutions. Screening for Mullerian anomalies in prediagnosed CAKUT girls may enable to provide timely counseling and to prevent gynecological complications.

Integrin alpha 2 is associated with tumor progression and postoperative recurrence in non-small cell lung cancer

BACKGROUND

Integrins are transmembrane proteins that mediate cell adhesion to extracellular matrix. Whereas expression of integrin alpha 2 is associated with motility, invasiveness and cellular differentiation in various tumors, the role of integrin alpha 2 in lung cancer has not been studied in detail. The aim of this study was to determine whether and how aberrant integrin alpha 2 expression in non-small cell lung cancer leads to different outcomes.

METHODS

We measured expression of integrin alpha 2 by quantitative polymerase chain reaction in 100 samples collected from non-small cell lung cancer patients who had undergone surgical resection. We assigned patients to high and low expression groups and analyzed survival. Cellular morphology, adhesion, proliferation, migration and invasion were examined in human lung cancer cell lines.

RESULTS

Among 100 cases, 41 were female, with a median age of 71 years. High expression of integrin alpha 2 in non-small cell lung cancer was associated with lower recurrence-free survival (P = 0.004). Overexpression of integrin alpha 2 in cell lines had no effect on cell proliferation or invasion but resulted in increased cell size (1416 μm2 versus 470 μm2 in H522 cells, P < 0.001; 1822 μm2 versus 1029 μm2 in H661 cells, P = 0.02), adhesion (P < 0.001 in H522 and H661 cells) and migration (gap area filled was 71% versus 36% in H522 cells, P < 0.001; 57% versus 26% in H661 cells, P = 0.001). These changes were suppressed by E7820, an inhibitor of integrin alpha 2.

CONCLUSIONS

Integrin alpha 2 may play a significant role in lung cancer adhesion and migration, and may lead to a higher risk of recurrence.

Detecting immunotherapy-sensitive subtype in gastric cancer using histologic image-based deep learning

Immune checkpoint inhibitor (ICI) therapy is widely used but effective only in a subset of gastric cancers. Epstein–Barr virus (EBV)-positive and microsatellite instability (MSI) / mismatch repair deficient (dMMR) tumors have been reported to be highly responsive to ICIs. However, detecting these subtypes requires costly techniques, such as immunohistochemistry and molecular testing. In the present study, we constructed a histology-based deep learning model that aimed to screen this immunotherapy-sensitive subgroup efficiently. We processed whole slide images of 408 cases of gastric adenocarcinoma, including 108 EBV, 58 MSI/dMMR, and 242 other subtypes. Many images generated by data augmentation of the learning set were used for training convolutional neural networks to establish an automatic detection platform for EBV and MSI/dMMR subtypes, and the test sets of images were used to verify the learning outcome. Our model detected the subgroup (EBV + MSI/dMMR tumors) with high accuracy in test cases with an area under the curve of 0.947 (0.901–0.992). This result was slightly better than when EBV and MSI/dMMR tumors were detected separately. In an external validation cohort including 244 gastric cancers from The Cancer Genome Atlas database, our model showed a favorable result for detecting the “EBV + MSI/dMMR” subgroup with an AUC of 0.870 (0.809–0.931). In addition, a visualization of the trained neural network highlighted intraepithelial lymphocytosis as the ground for prediction, suggesting that this feature is a discriminative characteristic shared by EBV and MSI/dMMR tumors. Histology-based deep learning models are expected to be used for detecting EBV and MSI/dMMR gastric cancers as economical and less time-consuming alternatives, which may help to effectively stratify patients who respond to ICIs.

A case of difficult-to-diagnose non-invasive papillary squamous cell carcinoma of the uterine cervix infected with human papilloma virus 6: A diagnostic pitfall

We encountered HPV6-positive cervical papillary squamous cancer (PSCC) that was difficult to diagnose. The case was initially diagnosed and treated for condyloma. To the best of our knowledge, this is the first report of HPV6 infection in PSCC.

Cerebral toxoplasmosis complicating lymphoplasmacytic lymphoma in partial remission

Toxoplasma gondii can develop toxoplasmic encephalitis (TE) in immunodeficient conditions such as AIDS and after organ transplantation. While some cases of TE with malignant lymphoma were reported, these cases occurred immediately after chemotherapy or when their diseases were active. Here we report the first Case of TE that occurred in patient who was in partial remission (PR) of lymphoplasmacytic lymphoma (LPL) for two years. A 76-year-old man was referred to our institute because of disturbance of consciousness, right arm weakness and paresthesia. A computed tomography (CT) scan detected multiple nodules in his brain. Magnetic resonance imaging (MRI) of the head detected multiple gadolinium-enhancing parenchymal lesions with hyperintense signals on T2-and diffusion-weighted images, located in both cerebral and cerebellar hemispheres. Blood test and cerebrospinal fluid (CSF) findings were unremarkable. His rapidly deteriorating consciousness precluded a chance of brain biopsy. Considering the limited efficacy of antimicrobials and the imaging findings that could be compatible with the diagnosis of malignant lymphoma, we suspected central nerve system (CNS) recurrence of LPL. Although chemotherapy was initiated, he died of respiratory failure just after chemotherapy. A pathological autopsy showed his cause of death was TE. To our knowledge, this is the first case of TE in long-term PR of malignant lymphoma. TE should be suspected when patients with malignant lymphoma present unexplained neurologic symptoms regardless of their treatment efficacy of lymphoma. (226/250 words).

Rectal neuroendocrine tumor with extracapsular lymph node metastasis: a case report

The presence of extramural tumor deposits without lymph node structure (EX) is an important prognostic factor in patients with colorectal carcinoma. However, there is no English literature on neuroendocrine tumor (NET) with EX. We report a patient with rectal NET with extracapsular metastasis of a regional lymph node that was considered to be EX. A 51-year-old Japanese woman with diabetes was referred to our hospital for further examination of a submucosal tumor in the lower rectum. She was diagnosed as having rectal NET by immunohistochemical analysis of a biopsy, and underwent laparoscopic low anterior resection with lymph node dissection and covering ileostomy. Pathological findings of the resected specimen showed that the primary tumor was NET-G1 without any lymphatic or venous invasion. A single metastatic deposit was found near the capsule of a NET-negative regional lymph node. She has been free from recurrence for nine months without adjuvant treatments. Extracapsular metastasis of NET on a dissected lymph node in our case was considered to correspond to EX as defined for colorectal carcinoma. This rare case suggests that NET can disseminate to form EX in a similar manner to colorectal carcinoma.

Retro-odontoid Pseudotumor: Two Cases of Intradural Ganglion Cysts Arising From the Odontoid Process with Syringobulbia

BACKGROUND

Ganglion cysts mostly occur in the knuckles and wrists, but they rarely present in the odontoid process and can cause neurological symptoms by compressing the spinal cord. They are mostly localized in the epidural space, but may very rarely appear in the intradural space. There are no reports of cases of intradural ganglion cyst involving syringobulbia.

CASE DESCRIPTION

We report the presentation and management of 2 cases of an intradural ganglion cyst of the odontoid process. Several treatment options for ganglion cysts of the odontoid process have been reported, such as rest and use of a neck collar, posterior decompression and fusion, and transoral anterior decompression. Because our 2 cases progressed rapidly and had severe neurological symptoms, surgical treatment was performed for rapid decompression and definitive pathological diagnosis. The mass was resected as much as possible using the lateral occipital fossa approach, and the operation was completed without dissection of the brain stem or manipulation of the syringobulbia. Postoperatively, neurological symptoms promptly improved, and the syringobulbia reduced.

CONCLUSIONS

For intradural ganglion cysts with syringobulbia, we suggest relief of the compression by resection of the mass and treatment of the syringobulbia in 2 stages, if necessary, to avoid the risk of damage to the brainstem.

Renal Effects after Pembrolizumab Treatment for Non-small Cell Lung Carcinoma

Immune checkpoint inhibitors (CPIs), including pembrolizumab, are becoming common oncological treatments. CPIs have been associated with a significant risk of developing immune-related adverse events (irAEs), such as nephritis and interstitial nephritis. However, the occurrence of glomerulonephritis has only rarely been reported. We herein present the case of a 75-year-old woman with non-small cell lung carcinoma (NSCLC) who developed proteinuria and microscopic hematuria during treatment with pembrolizumab. Renal biopsy revealed tubulointerstitial nephritis and IgA nephropathy. Considering that a urinalysis showed no abnormality before treatment, the condition might have been induced by pembrolizumab. In this report, we focus on the correct diagnosis and management of renal irAEs, which remain controversial.

A case of primary breast angiosarcoma with multiple discontinuous small lesions

BACKGROUND

Angiosarcoma of the breast is rare. It carries a poor prognosis because of its high risk of local recurrence and distant metastases. Presently, there are still no established systemic therapies. Thus, the main treatment strategy for breast angiosarcoma is complete resection. This underscores the importance of closely monitoring the spread of the tumor lesion, particularly for multifocal angiosarcoma, and to plan an optimal operative procedure. We herein present the successful surgical treatment of a rare case of multifocal primary breast angiosarcoma.

CASE PRESENTATION

A 43-year-old woman visited our hospital with a growing lump on her right breast accompanied by pain. Clinical and radiological examinations revealed a well-circumscribed 40-mm-diameter tumor at the inner lower quadrant of her right breast. Histological examination of a needle biopsy specimen revealed angiosarcoma. Based on a precise evaluation of the tumor by contrast-enhanced MRI and contrast-enhanced CT scan, a wide local excision with sufficient margins was performed. In the resected specimen, three discontinuous small lesions of angiosarcoma were observed around the main tumor. Therefore, total mastectomy was additionally performed. Pathological examination revealed two other small nodules of angiosarcoma in the remnant right breast, which appeared to be close but not continuous to the defective part of the initial resection. Postoperative follow-up at 1 year showed no signs of recurrence or distant metastasis. Multifocal primary breast angiosarcoma is extremely rare with only two previous reports describing its multifocality.

CONCLUSIONS

Owing to its rarity, a standardized surgical treatment for breast angiosarcoma remains controversial. Our case suggests that primary breast angiosarcoma may occasionally present with multifocal tumor. Thus, it is important to keep in mind the multifocality of breast angiosarcoma when assessing its spread by diagnostic imaging and when planning the surgical strategy.

A case of delayed exacerbation of interstitial lung disease after discontinuation of temsirolimus

Temsirolimus is an inhibitor of mammalian target of rapamycin and interstitial lung disease (ILD) is known to be one of the adverse events associated with temsirolimus, which usually improves rapidly after discontinuation of the drug and rarely worsens thereafter. Herein, we report a case of delayed exacerbation of ILD after discontinuation of temsirolimus for metastatic renal cell carcinoma in an 86-year-old male with chronic ILD. The patient developed gradually worsening dyspnea five weeks after an initiation of temsirolimus and was admitted to our facility. On his admission, although a pulmonary function test revealed a decreased diffusion capacity, there was no obvious progression of ILD on HRCT scan. His dyspnea once improved after discontinuation of temsirolimus, but it recurred and acute exacerbation of ILD was diagnosed 40 days after his last administration of temsirolimus. He received high-dose steroid therapy, however, he deteriorated and died. Histopathological examination of the lungs at autopsy revealed overlapping diffuse alveolar damage with chronic interstitial changes. In the present case, since there were no specific factors that could have caused acute exacerbation of ILD except for temsirolimus, it was considered to contribute to the exacerbation of underlying ILD. In conclusion, physicians should be aware of the possibility of temsirolimus-induced ILD not only while the medication is administered, but also even after it is discontinued. It is important to carefully interview the patient and to recognize the value of physiological tests, such as respiratory function tests and blood gas analysis, as well as imaging findings on HRCT.

Metastatic hepatocellular carcinoma of the maxillary sinus: a rare autopsy case without lung metastasis and a review

A rare case of metastatic hepatocellular carcinoma (HCC) of the maxillary sinus in a 67-year-old man is reported along with the findings at autopsy. A fine needle aspiration biopsy specimen revealed a characteristic tumour structure resembling primary HCC. At autopsy, metastatic lesions were recognized in the bilateral adrenals, spleen, sternum, vertebrae and lymph node at the lesser curvature of the stomach, but not in the lung, suggesting that the HCC had metastasized to the maxillary sinus via the plexus venous vertebralis and/or the azygos vein, or lymph duct. In our reviewed 29 cases of metastatic HCC in the oro-maxillofacial region, most patients were men in the 50- to 70-year age range. At least 11 cases did not have lung metastasis, and in 18, metastasis to the oro-maxillofacial region was the first sign of HCC. One should be aware of the possibility to encounter the oral lesion as first sign of metastatic HCC.

Sp family members stimulate transcription of the hex gene via interactions with GC boxes

The 5'-flanking region of the mouse Hex gene was examined in order to identify transcription factors regulating its expression in hepatocytes and haematopoietic cells. We have identified two further GC boxes (GC boxes 3 and 4 at nucleotide positions -149 to -140 and -79 to -70, respectively), i.e. in addition to the two previously determined ones (GC boxes 1 and 2 at nucleotide positions -197 to -188 and -176 to -167, respectively). Luciferase reporter assays revealed that all four GC boxes are transcriptionally active in both MH(1)C(1) rat hepatoma and K562 human chronic myelogenous leukemia cells. Electrophoretic mobility shift assays with specific competitors and antibodies showed that members of the Sp family, namely Sp1 and Sp3, bind to these GC boxes. Overexpression of Sp1 and Sp3 in Drosophila SL2 cells stimulated transcription of the Hex gene through interactions with GC boxes 1 to 4, Sp1 being a more potent activator than Sp3. Thus, we conclude that Sp1 and Sp3 stimulate transcription of the Hex gene in both MH(1)C(1) and K562 cells.

Identification of the bphA4 gene encoding ferredoxin reductase involved in biphenyl and polychlorinated biphenyl degradation in Pseudomonas sp. strain KKS102

The nucleotide sequence of the downstream region of the bph operon from Pseudomonas sp. strain KKS102 was determined. Two open reading frames (ORF1 and ORF2) were found in this region, and the deduced amino acid sequence of ORF2 showed homology with the sequences of four ferredoxin reductases of dioxygenase systems. When this region was inserted just upstream of the bph operon, which does not contain a gene encoding ferredoxin reductase, biphenyl dioxygenase activity was detected. The 24- and 44-kDa polypeptides predicted from the two open reading frames were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Crude extract which contained the products of ORF2 and bphA1A2A3 showed cytochrome c reduction activity. These data clearly suggest that ORF2 encodes ferredoxin reductase. The deduced amino acid sequence of ORF1 does not show significant homology with the sequences of any other proteins in the SWISS-PROT data bank, and the function of ORF1 is unknown.