Well-differentiated neuroendocrine tumor (NET) and poorly differentiated neuroendocrine carcinoma (NEC) are distinct entities with different biological behavior. However, difficult cases showing equivocal morphology have been reported in some organs. Herein, we report a case of primary hepatic neuroendocrine neoplasm (NEN) with ambiguous histopathological features admixed with conventional hepatocellular carcinoma (HCC). A 70-year-old man with untreated chronic hepatitis B underwent left medial sectionectomy because of two incidental liver masses. On pathological examination, one of the resected tumors had intermingling NEN and HCC components. The NEN component consisted of relatively uniform tumor cells proliferating in trabecular, cord-like, or solid patterns with peripheral nuclear palisading. The tumor cells were immunopositive for synaptophysin, chromogranin A, cluster of differentiation 56 (CD56), and focally hepatocyte paraffin 1. p53 showed wild-type expression. The Ki-67 labeling index was 27% at the hot spot. Eleven months after the surgery, he died of a cerebral hemorrhage without evidence of recurrent liver cancer. The intermediate degree of differentiation and the modest proliferative activity can challenge the distinction between NEC and NET G3. While the coexisting HCC indicates NEC rather than NET in a pathogenetic viewpoint, such ambiguous tumor may not be as aggressive as typical NECs.

A 71-year-old man with bone metastasis of hormone-sensitive prostate cancer was treated with androgen deprivation therapy and apalutamide. Radium-223 and radiation therapy were administered after it become castration resistant. Although prostate-specific antigen levels remained low, multiple subcutaneous metastases of neuroendocrine prostate cancer were observed. A review of the pre-treatment prostate needle biopsy revealed a small component with features suggestive of neuroendocrine differentiation. Phosphatase and tensine homolog loss and tumor protein p53 overexpression were observed, confirming the diagnosis of aggressive variant prostate cancer. Platinum-based chemotherapy was administered; however, the patient died 28 months after diagnosis. In this case, if the diagnosis of aggressive variant prostate cancer had been made at an earlier time by biopsy specimens, there might have been a possibility to improve the prognosis by the earlier introduction of the platinum-based regimen.
UNASSIGNED: The online version contains supplementary material available at 10.1007/s13691-024-00673-7.

UNASSIGNED: Mixed adenoneuroendocrine carcinoma is a rare tumor of the gastrointestinal tract with double differentiation into adenomatous and neuroendocrine carcinoma, each component with at least 30%.
UNASSIGNED: A 60-year-old female with acute abdominal pain. Surgical treatment was decided, finding a tumor at the level of the cecum and ascending colon, a right hemicolectomy and ileostomy were performed.
UNASSIGNED: Mixed adenoneuroendocrine carcinoma can appear in various organs. They are highly malignant tumors, with a high risk of metastasis.
UNASSIGNED: These tumors do not present symptoms or specific radiological or laboratory findings; diagnosis depends on postoperative histopathological and immunohistochemical studies.
UNASSIGNED: El carcinoma adenoneuroendocrino mixto es un tumor raro del tracto gastrointestinal con doble diferenciación en carcinoma adenomatoso y neuroendocrino, cada componente con al menos el 30%.
UNASSIGNED: Mujer de 60 años con cuadro de dolor abdominal agudo. Se decide tratamiento quirúrgico, encontrando un tumor a nivel de ciego y colon ascendente, y se realizan hemicolectomía derecha e ileostomía.
UNASSIGNED: El carcinoma adenoneuroendocrino mixto puede aparecer en diversos órganos. Son tumores muy malignos, con alto riesgo de metástasis.
UNASSIGNED: Estos tumores no presentan síntomas ni hallazgos radiológicos o de laboratorio específicos; el diagnóstico depende de estudios histopatológicos e inmunohistoquímicos posoperatorios.

UNASSIGNED: Solid papillary carcinoma (SPC) accounts for approximately 1% of all breast cancer cases and occurs primarily in postmenopausal women. We report a rare SPC with invasion in the male breast.
UNASSIGNED: A 73-year-old Japanese man presented with bloody nipple discharge and a palpable left breast mass. Mammography revealed a well-defined high-concentration mass. Ultrasonography scans demonstrated an intracystic 10 mm mass under the left nipple without enlarged axillary lymph nodes. A core needle biopsy revealed a ductal carcinoma with nuclear grade 1, which excluded an invasive carcinoma. Magnetic resonance imaging exhibited a 7 mm intense early enhancement in the left breast. A left mastectomy and sentinel lymph node biopsy were performed. The patient was diagnosed with pathological stage IA (T1b N0 M0) breast carcinoma, an invasive pure SPC type without neuroendocrine markers. The patient was treated with oral tamoxifen and survived without any recurrence for 12 months.
UNASSIGNED: Invasive SPC of the male breast may occur as a palpable mass or nipple discharge in older men and has a good prognosis.

Skeletal muscle metastasis of prostate cancer is a very rare phenomenon that has only been described in limited case reports. In this study, we present a case of neuroendocrine prostate cancer with muscle metastasis, a histological subtype associated with a grim prognosis. This case illustrates the potential efficacy of urgent surgical resection of the metastatic muscle mass, followed by adjuvant radiation therapy, as a suitable management strategy for this condition. However, a comprehensive understanding of the biological characteristics of neuroendocrine prostate cancer is imperative in our fight against this lethal form of the disease and in the prevention of metastatic spread.

This article describes the process of multidisciplinary team (MDT) discussion and comprehensive treatment of a case of advanced gastric cancer that tested positive for programmed death ligand 1 (PD-L1). During diagnosis, the patient presented with advanced gastric cancer and numerous unresectable metastases in the lesser omental lymph nodes, both lungs, liver, and left parietal occipital lobe. A meeting was arranged for the departments of oncology, gastrointestinal surgery, radiotherapy, imaging, and pathology to discuss the case. Initially, the patient had a partial response to the first-line treatment, which was a combination of pembrolizumab and chemotherapy. However, after nineteen months, the patient presented with a metachronous isolated lesion in the left frontal lobe. After mutual agreement among the oncology, brain surgery, gastrointestinal surgery, radiotherapy, imaging, and pathology departments, the intracranial lesion underwent resection. Following this, the operation was supplemented by stereotactic radiation therapy (SRT) and whole-brain radiation therapy (WBRT). The patient showed excellent signs of recovery after the operation, and her general condition remained favorable after 16 months of follow-up. Nonetheless, the outlook for patients facing advanced-stage gastric cancer remains distressing. Through multidisciplinary team (MDT) discussions, patients diagnosed with advanced gastric cancer can receive standardized diagnostic and treatment approaches to develop reasonable and personalized comprehensive treatment plans. Such plans help to improve the quality of life of patients and effectively prolong their survival time.

A 66-year-old male was diagnosed with cT4N0M1b small-cell neuroendocrine carcinoma of the prostate. Four months after the administration of combined androgen blockade, multiple novel metastatic regions in the lung and liver and progression of bone metastasis were observed. The patient was referred to our hospital because of biochemical and radiographic progression after four cycles of docetaxel as a first-line therapy for castration-resistant prostate cancer. Transurethral resection of the prostate and hepatic biopsy revealed small-cell carcinoma with positive expression of neuroendocrine markers. The FoundationOne CDx next-generation sequencing test revealed several pathogenic variants, including BRCA2 (W1692fs*3), KEAP1 (R320W), and TP53 (C2385) mutation. After four cycles of chemotherapy with carboplatin plus etoposide (CE), the metastatic regions regressed markedly. The prostate-specific antigen (PSA) and neuron-specific enolase (NSE) level decreased by 96.9% and 91.6%, respectively. However, 2 months after the completion of four cycles of CE, elevation of tumor marker levels, and re-growth of the metastatic regions were observed. Although olaparib, a poly (ADP-ribose) polymerase inhibitor (PARPi), achieved a 45.2% decrease in NSE, the patient rejected to continue therapy because of G2 adverse events. After receiving an additional two cycles of CE and one cycle of cabazitaxel, the patient died because of cancer progression 24 months after the initial treatment for prostate cancer. Here, we present a case of BRCA2-altered small-cell neuroendocrine prostate cancer treated with both platinum-containing chemotherapy and PARPi. Both therapies achieved an initial response; however, durable responses were not obtained. Additional discussion regarding the optimal treatment strategy for BRCA-altered small-cell/neuroendocrine prostate cancer is required.

BACKGROUND: Both hepatoid adenocarcinoma of the stomach (HAS) and neuroendocrine differentiation (NED) are rare histological subtypes of gastric cancer with unique clinicopathological features and unfavorable outcomes. HAS with NED is even rarer.
METHODS: Here, we report a 61-year-old man with HAS with NED, as detected by gastric wall thickening by positron emission tomography/computed tomography for a pulmonary nodule. Distal gastrectomy was performed, and pathological examination led to the diagnosis of HAS with NED. However, liver metastases occurred 6 mo later despite adjuvant chemotherapy, and the patient died 27 mo postoperatively.
CONCLUSIONS: We treated a patient with HAS with NED who underwent adjuvant chemotherapy after radical surgery and still developed liver metastases. We first report the detailed processes of the treatment and development of HAS with NED, providing an important reference for the clinical diagnosis and treatment of this condition.

Mucinous carcinoma of the breast is rare representing 2% of all breast carcinomas. It can be classified as either a pure or a mixed type. Pure mucinous breast carcinoma has a less aggressive behavior compared with mixed breast mucinous carcinoma. The latter shows frequent neuroendocrine differentiation.

Primary invasive breast carcinoma with neuroendocrine differentiation is an uncommon presentation. We hereby report a case diagnosed as invasive ductal carcinoma with neuroendocrine differentiation in a 52-year-old female patient who presented with a painless right breast lump.