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A rare Japanese case with a NUT midline carcinoma in the nasal cavity: A case report with immunohistochemical and genetic analyses

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Abstract

Background

NUT (nuclear protein in testis) midline carcinoma (NMC) is a recently described aggressive malignancy that is genetically defined by rearrangements of the NUT locus at 15q14. In approximately two-thirds of cases, the characteristic t(15;19) results in the fusion oncogene BRD4-NUT. Only 10 sinonasal NMCs have been documented, none of which were Japanese cases.

Case presentation

An 18-year-old woman was admitted because of a rapidly progressing tumor in the nasal cavity. A biopsy revealed an undifferentiated neoplasm without squamous differentiation. The tumor cells had round to oval nuclei with vesicular chromatin, prominent nucleoli, and scant cytoplasm. Immunohistochemical staining demonstrated a strong positivity for vimentin and NUT, with focal CD138 and only spotty EMA and cytokeratin AE1/AE3 staining. Cytogenetic and fluorescence in situ hybridization analyses revealed a t(15;19) and BRD4-NUT gene rearrangement. Direct sequencing identified the in-frame fusion of exon11 of BRD4 with exon2 of NUT. The patient was transferred to another hospital for chemoradiotherapy.

Conclusion

We herein describe the first Japanese case with an NMC of the sinonasal cavity, providing detailed and unambiguous cyto- and molecular genetic information on BRD4-NUT-rearrangement. The accumulation of cases with well-documented genetic data should provide clues to the treatment of this tumor entity.

Introduction

Several malignant tumors of the sinonasal tract may present with an undifferentiated morphology [6], [20]. Overall, these tumors pose significant diagnostic challenges to attending surgical pathologists, especially in cases in which a limited amount of biopsy material is available [6] and in cases that do not exhibit the typical immunohistochemical results [3]. Among these sinonasal malignant neoplasms, nuclear protein in testis (NUT) midline carcinoma (NMC) is a recently recognized entity that is characterized by a poor prognosis [1], [20].

The current recognition of the NMC entity is genetically defined by rearrangements of the NUT locus at 15q14, resulting in a fusion transcript with a member of the bromodomain-containing protein (BRD) family, usually BRD4 located on chromosome 19p13.1 [7], [10]. As NMC is a recently described tumor entity, it is still unfamiliar to most pathologists [14], [16], [20]. The histological features of tumors that have been reported as NMCs range from entirely undifferentiated carcinomas to carcinomas with prominent squamous differentiation [2], [3], [4], [10], [19]. Thus, the diagnosis of NMC simply based on morphology is difficult. Until recently, only one molecular method within the realm of diagnostic pathology, i.e., fluorescence in situ hybridization (FISH), was available for the robust demonstration of a rearrangement of the NUT gene [3], [8], [19]. Consequently, this entity has been commonly undiagnosed or misdiagnosed in clinical pathology practice, and comprehensive information, such as the correlation between the molecular features and the biological behaviors of this cancer, is limited. Since the identification of a somatic rearrangement involving the NUT gene in NMC [7], only a few reports have determined the fusion gene in clinical specimens using a direct sequencing method [7], [9], [12], [23]. NMCs are rare [1], [10], [20], and the geographic distribution of reported cases has been concentrated in the United States [1]. NMCs most often occur in the midline, including the head and neck, and the thorax [10], [20]. Although the sinonasal tract is considered a preferential site in the head and neck region, only 10 sinonasal NMCs have been documented [2], [3], [8], [13], [19], none of which were Japanese cases.

In this article, we describe a new Japanese case with NMC in the nasal cavity; the NMC was diagnosed using immunohistochemistry with a highly sensitive and specific NUT monoclonal antibody [11]. In addition, a BRD4-NUT fusion gene, as the mechanism of NUT overexpression, was defined by karyotyping as well as molecular methods, including FISH and RT-PCR direct sequencing.

Section snippets

Clinical summary

An 18-year-old woman sought medical advice because of nasal discharge containing blood accompanied by pain with a 1-month duration. A computed tomography scan performed at the time of hospitalization revealed a mass in the right nasal cavity, and maxillary and ethmoidal sinus (Fig. 1). The mass involved the ethmoid bone (Fig. 1, arrow). A biopsy was performed.

Histopathologic and immunohistochemical examination

All the tissues were fixed in 10% buffered formalin and were embedded in paraffin after routine processing, followed by sectioning and staining with hematoxylin and eosin (H&E). Immunostaining was performed using antibodies for the following antigens: CD34 class II (DAKO, Glostrup, Denmark), CD45 (DAKO), CD56 (Leica Biosystems, Newcastle, United Kingdom), CD99 (DAKO), CD138/Syndecan-1 (DAKO), c-kit (DAKO), cytokeratin AE1/AE3 (DAKO), desmin (DAKO), epithelial membrane antigen (EMA, DAKO), hCG

Direct sequencing

BRD4-NUT fusion cDNA was amplified using PCR with Phusion (New England BioLabs, Beverly, MA, USA); direct sequencing was then performed as described previously [7]. The primers BR2276F (AAGTTGATGTGATTGCCGGCTCCTC) and NUT1194R (GAGGTCTCTGGGCTTTACGCTGACG) were used [7]. Gel-purified PCR products were cycle-sequenced by the incorporation of ABI PRISM Big Dye Terminators (Perkin-Elmer, Inc., Wellesley, MA) and analyzed using an ABI 3130 sequencer (Life Science Technologies, Carlsbad, CA, USA).

Pathological findings

The small amount of biopsy material that was obtained revealed an undifferentiated neoplasm with necrosis (Fig. 3a). The tumor cells had round to oval nuclei with vesicular chromatin, prominent nucleoli, and scant cytoplasm (Fig. 3b). Frequent mitotic figures (10/5 hpf) were observed (Fig. 3b, arrow). Squamous differentiation was not identified.

Immunohistochemical staining demonstrated a strong vimentin positivity (Fig. 4a) with focal CD138 (Fig. 4b) and only spotty EMA (Fig. 4c) and cytokeratin

Treatment and follow up

The patient was transferred to another hospital to undergo chemoradiotherapy (the details of which are unknown), which resulted in the almost complete disappearance of the tumor. The patient is alive and well at 12 months after her diagnosis.

Discussion

The histologic features of NMC are, unfortunately, not pathognomonic, since the morphology is that of a poorly differentiated carcinoma with or without squamous differentiation [2], [3], [4], [10], [19]. Several malignant tumors occurring in the sinonasal tract may exhibit an undifferentiated morphology [3], [6], [20]. The differential diagnosis of these tumors includes hemato-lymphoid malignancies, melanomas, Ewing sarcoma/primitive neuroectodermal tumors, rhabdomyosarcoma, olfactory

Conflict of interest

The authors have no conflicts of interest to declare.

Acknowledgments

We appreciate the technical assistance of Ms. Kiyoko Nagura and Mr. Hisaki Igarashi.

This case was presented at the Japanese Pathological Society Chubu Meeting on July 13–14, 2013, in Nagoya.

This contribution was supported, in part, by Grants-in-Aid for the U.S.-Japan Cooperative Medical Science Program; the National Cancer Center Research and Development Fund; Grant for priority areas from the Japanese Ministry of Education, Culture, Sports, Science and Technology [221S0001]; and Grants-in-Aid

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