Case report: NUT carcinoma with MXI1::NUTM1 fusion characterized by abdominopelvic lesions and ovarian masses in a middle-aged female

MAD::NUT Fusion Sarcoma: A Sarcoma Class With NUTM1, NUTM2A, and NUTM2G Fusions and Possibly Distinctive Subtypes

NUT fusion-associated cancers are heterogeneous and include NUT carcinoma and an emerging group with non-BRD4/BRD3/NSD3 fusion partners. In this study, we characterized 11 tumors harboring MAD::NUT fusions (10/11 in female patients; median age: 48 years; range: 1-67 years), all histologically different from NUT carcinoma. Eight cases were identified via sequencing database review and 3 were diagnosed prospectively. Eight (73%) patients presented with multifocal disease, including 6 with disseminated peritoneal tumors; 3 (27%) presented with solitary colonic, pulmonary, or orbital masses. Nine (82%) tumors harbored NUTM1 fusions, with MXI1 (5/9; 56%), MXD4 (2/9; 22%), and MGA (2/9; 22%). One tumor each harbored MXD4::NUTM2G and MXI1::NUTM2A fusions. The 9 MXD4/MXI1-rearranged sarcomas were high-grade, with epithelioid-to-spindle cell cytomorphology, amphophilic cytoplasm, vesicular nuclei, and prominent nucleoli. Histologic features included infiltrative growth (7/7 assessable tumors), rhabdoid morphology (7/9; 78%), prominent collagen (3/9; 33%), multinucleated tumor cells (2/9; 22%), and myxoid stroma (1/9; 11%). MXD4/MXI1-rearranged sarcomas expressed desmin (3/7; 43%) and keratin(s) (3/7; 43%), and not p63 (6 tumors), CD34 (5 tumors), or S-100 (5 tumors). The adult MGA::NUTM1 fusion sarcoma exhibited some cytologic overlap with MXD4/MXI1-rearranged sarcomas but showed lower grade myxoid spindle cell regions, microcystic spaces, and S-100 expression. The pediatric MGA::NUTM1 fusion sarcoma was low-grade with CD34/S-100 coexpression. Immunohistochemistry demonstrated NUTM1 expression in NUTM1-rearranged sarcomas (5/5), and weak and no expression in NUTM2A- and NUTM2G-rearranged sarcomas, respectively. Gene expression profiling demonstrated sarcomas with MXD4/MXI1::NUTM1/NUTM2A/NUTM2G fusions clustered separately from NUT carcinoma. Follow-up was available for 9 patients (82%; median length: 1.8 years; range: 2 months to 8.2 years). Four of 7 patients with MXD4/MXI1-rearranged sarcomas died of disease (median survival: 1.3 years; range: 5 months to 4.8 years), 1 entered hospice at 2 months, 1 was alive with pericardial masses at 2.8 years, and 1 was alive with no evidence of disease at 8.2 years. The adult with the MGA::NUTM1 fusion sarcoma died of other causes at 4.5 years; the child was alive without disease at 11 months. We conclude that MAD::NUT fusions define a sarcoma class distinct from NUT carcinoma. Among this group, MGA::NUTM1 fusion sarcomas might represent a distinctive subset. NUTM1 immunohistochemistry does not reliably detect NUTM2A/NUTM2G-rearranged sarcomas.

Pulmonary Nuclear protein in Testis (NUT) carcinoma: clinical, molecular characteristics, and treatment strategies

BACKGROUND

Pulmonary nuclear protein in testis (NUT) carcinoma is a rare and aggressive malignancy that often exhibits clinical and pathological features overlapping with other thoracic malignancies, posing significant challenges for accurate diagnosis and leading to poor treatment outcomes.

METHOD

We conducted a retrospective analysis of five patients diagnosed with pulmonary NUT carcinoma between 2020 and 2023. Comprehensive clinical, imaging, histopathological, and molecular data and survival outcomes were collected.

RESULTS

The cohort included three females and two males, with a median age of 44 years. Clinical features commonly involved centrally located masses with mediastinal invasion. Distant metastases to bones, pleura, and lungs were confirmed in 60% of cases. Diagnostic confirmation was achieved through NUT protein positivity via IHC and FISH rearrangements in all five patients. RNA sequencing identified BRD3-NUTM1 fusions in 60% (3/5) patients. Chemotherapy was employed as the initial treatment strategy but showed limited efficacy in advanced stages. Among two patients undergoing surgical resection, better outcomes were achieved in the patient receiving adjuvant therapy with overall survival (OS) exceeding 36 months. Immunotherapy demonstrated limited benefit, likely attributable to low PD-L1 expression and an immunologically "cold" tumor microenvironment. Despite multimodal treatment approaches, three out of five patients in advanced pulmonary NUT carcinoma died to the disease, with OS ranging from 6 to 15 months.

CONCLUSION

Advanced molecular techniques are critical for diagnosing pulmonary NUT carcinoma, but survival outcomes remain poor. Surgical resection with adjuvant therapy offers better outcomes for early-stage patients, while chemotherapy and immunotherapy show limited efficacy in metastatic cases due to the tumor's aggressive behavior. Early detection and innovative therapies are essential for improving outcomes.

Exploring cytologic features and potential diagnostic challenges of metastatic NUT carcinoma to the parotid gland: A case report and a comprehensive literature review

NUT carcinoma (NC) is a highly aggressive, poorly differentiated carcinoma that harbors a t(15:19) translocation, leading to the fusion of the NUTM1 gene. While the upper aerodigestive tract along the midline (head, neck, thorax, and mediastinum) is commonly reported as the primary site of NC, subsequent cases have emerged in diverse locations. Achieving a definitive diagnosis based solely on morphology is challenging; however, it can be achieved using immunohistochemistry (IHC) specific to the NUT antibody or by demonstrating the characteristic BRD4::NUTM1 fusion. Accurate and timely diagnosis can potentially inform patient management and guide treatment. While histologic documentation of NC is commonly found, there is a limited description of its cytologic features. A 39-year-old male with a history of sinonasal squamous cell carcinoma (SCC) presented with a right parotid mass aspirated via fine needle aspiration cytology (FNA). Histologic examination of the previous sinonasal pathology reviewed at our institution revealed sheets of primitive-appearing, monotonous, undifferentiated cells with distinct, prominent nucleoli. Additionally, there were foci of abrupt keratinization, accompanied by a notable neutrophilic infiltrate. The initial diagnosis of SCC was reclassified to NC and confirmed through NUT IHC and molecular testing. Although the parotid FNA initially suggested the possibility of a variety of small round blue cell tumors, it exhibited morphological similarities to the sinonasal tumor, leading to the diagnosis of metastatic NC. Cytomorphologic features of NC are limited and can overlap with various small round blue cell tumors. Correct classification is especially pivotal in the era of targeted therapy, considering the ongoing development and evaluation of BET inhibitors targeting BRD4.