Navigating HER2-Low Testing in Invasive Breast Cancer: Update Recommendations for Pathologists.

The article discusses the importance of accurately distinguishing HER2-low from HER2-negative breast cancer, as novel ADCs have demonstrated activity in a large population of patients with HER2-low-expressing BC. While current guidelines recommend a dichotomous classification of HER2 as either positive or negative, the emergence of the HER2-low concept calls for standardization of HER2 testing in breast cancer, using currently available assays to better discriminate HER2 levels. This review covers the evolution and latest updates of the ASCO/CAP guidelines relevant to this important biomarker in breast cancer, including still-evolving concepts such as HER2 low, HER2 heterogeneity, and HER2 evolution. Our group presents the latest Mexican recommendations for HER2 status evaluation in breast cancer, considering the ASCO/CAP guidelines and introducing the HER2-low concept. In the era of personalized medicine, accurate HER2 status assessment remains one of the most important biomarkers in breast cancer, and the commitment of Mexican pathologists to theragnostic biomarker quality is crucial for providing the most efficient care in oncology.

Myxoid Endometriosis: An Entity That Can Cause Confusion with Malignant Entities.

Myxoid endometriosis, a rare entity, is part of the histological changes that can occur in endometriosis. Pathologists must know the histological guidelines for the morphological recognition of this entity, as well as the histochemical and immunohistochemical techniques that support diagnosis, and define the morphological characteristics of myxoid endometriosis. In the present work, we propose diagnostic guidelines and primary differential diagnoses using special histochemical techniques and immunohistochemical reactions to recognize this entity.

The Ring Study: an international comparison of PD-L1 diagnostic assays and their interpretation in non-small cell lung cancer, head and neck squamous cell cancer and urothelial cancer.

PD-L1 immunohistochemistry has been approved as a diagnostic assay for immunotherapy. However, an international comparison across multiple cancers is lacking. This study aimed to assess the performance of PD-L1 diagnostic assays in non-small cell lung cancer (NSCLC), head and neck squamous cell cancer (HNSCC) and urothelial cancer (UC). The excisional specimens of NSCLC, HNSCC and UC were assayed by Ventana SP263 and scored at three sites in each country, including Australia, Brazil, Korea, Mexico, Russia and Taiwan. All slides were rotated to two other sites for interobserver scoring. The same cohort of NSCLC was assessed with Dako 22C3 pharmDx PD-L1 for comparison. The PD-L1 immunopositivity was scored according to the approved PD-L1 scoring algorithms which were the percentage of PD-L1-expressing tumour cell (TC) and tumour proportion score (TPS) by Ventana SP263 and Dako 22C3 staining, respectively. In NSCLC, the comparison demonstrated the comparability of the SP263 and 22C3 assays (cut-off of 1%, κ=0.71; 25%, κ=0.75; 50%, κ=0.81). The interobserver comparisons showed moderate to almost perfect agreement for SP263 in TC staining at 25% cut-off (NSCLC, κ=0.72 to 0.86; HNSCC, κ=0.60 to 0.82; UC, κ=0.68 to 0.91) and at 50% cut-off for NSCLC (κ=0.64 to 0.90). Regarding the immune cell (IC) scoring in UC, there was a lower correlation (concordance correlation coefficient=0.10 to 0.68) and poor to substantial agreements at the 1%, 5%, 10% and 25% cut-offs (κ= -0.04 to 0.76). The interchangeability of SP263 and 22C3 in NSCLC might be acceptable, especially at the 50% cut-off. In HNSCC, the performance of SP263 is comparable across five countries. In UC, there was low concordance of IC staining, which may affect treatment decisions. Overall, the study showed the reliability and reproducibility of SP263 in NSCLC, HNSCC and UC.

Hemangioendotelioma epitelioide cutáneo extenso multifocal agresivo. Informe de un caso / Aggressive multifocal extensive cutaneous epithelioid haemagioendothelioma. A case report

El hemangioendotelioma epitelioide es un tumor vascular infrecuente, descrito por primera vez en 1975 por Dail y Liebow como un carcinoma bronquioloalveolar. Habitualmente, se comporta como una neoplasia de bajo grado; sin embargo, se han descrito casos en los que el tumor manifiesta una elevada agresividad, extendiéndose con rapidez por todo el organismo. Presentamos el caso de un hombre de 41 años con dermatosis en muslo izquierdo y extensión rápida a abdomen, cuyo diagnóstico inicial fue de un carcinoma metastásico vs. linfoma. En la revisión de laminillas, se confirmó el diagnóstico de hemangioendotelioma epitelioide de piel, iniciando tratamiento con radioterapia. Este tumor afecta excepcionalmente la piel, habiéndose descrito pocos casos en la literatura médica.(AU)

Epithelioid haemangioendothelioma is a rare vascular tumor, first described in 1975 by Dail and Liebow as a bronchioloalveolar carcinoma. Although it usually behaves like a low-grade neoplasm, cases have been reported in which the tumor shows a high grade of malignancy, spreading rapidly throughout the body. We present the case of a 41-year-old man with dermatosis in the left thigh with rapid extension to the abdomen; the initial differential diagnoses were metastatic carcinoma versus lymphoma. When the histopathology was re-examined, a diagnosis of skin epithelioid hemangioendothelioma was confirmed and treatment with radiotherapy was initiated. This tumour rarely affects the skin; there are only a few previously reported cases.(AU)

[Aggressive multifocal extensive cutaneous epithelioid haemagioendothelioma. A case report]. / Hemangioendotelioma epitelioide cutáneo extenso multifocal agresivo. Informe de un caso.

Epithelioid haemangioendothelioma is a rare vascular tumor, first described in 1975 by Dail and Liebow as a bronchioloalveolar carcinoma. Although it usually behaves like a low-grade neoplasm, cases have been reported in which the tumor shows a high grade of malignancy, spreading rapidly throughout the body. We present the case of a 41-year-old man with dermatosis in the left thigh with rapid extension to the abdomen; the initial differential diagnoses were metastatic carcinoma versus lymphoma. When the histopathology was re-examined, a diagnosis of skin epithelioid hemangioendothelioma was confirmed and treatment with radiotherapy was initiated. This tumour rarely affects the skin; there are only a few previously reported cases.

Case Report: Uterine Adenosarcoma With Sarcomatous Overgrowth and Malignant Heterologous Elements.

A 46- year-old woman presented a uterine adenosarcoma originating in the lower uterine segment. The diagnosis was made in an endometrial biopsy and confirmed in the pathological examination of the complete surgical specimen, both identifying heterologous malignant elements. In addition, complementary immunohistochemical studies were performed. We reviewed the literature, illustrating the clinical and morphological characteristics and the differential diagnoses to be evaluated.

Timoma pleural primario con presentación clínica de mesotelioma maligno / Primary pleural thymoma presenting as a malignant mesothelioma. A case report

Los timomas ectópicos rara vez se presentan como tumores pleurales. Informamos el caso de un timoma ectópico que se manifiesta clínica y radiológicamente como mesotelioma maligno en una mujer de 46 años quien presentó dolor torácico, disnea y pérdida de peso. Se realizó resección del tumor con diagnóstico patológico definitivo de timoma pleural ectópico B2 de acuerdo con la OMS y Masaoka estadio IVa. No se observó continuidad con el tejido del timo normal, por lo que pensamos que el timoma se originó de tejido ectópico en pleura (AU)

Ectopic thymoma is rarely found in the pleura. We report a case of a 46 year old female who presented with chest pain, shortness of breath and weight loss and with the clinical and radiological signs of a malignant mesothelioma. After surgical resection, the tumour was diagnosed as a pleural thymoma WHO type B2 and Masaoka stage IVa. As there was no continuity with the normal thymus tissue, the thymoma was thought to have arisen from ectopic thymic tissue in the pleura (AU)

Linfoma primario del apéndice cecal con presentación clínica de apendicitis aguda / Primary lymphoma of the appendix presenting as acute appendicitis

Los linfomas primarios de apéndice son neoplasias malignas poco frecuentes que, cuando aparecen, pueden presentarse como un cuadro de apendicitis aguda. El estudio histopatológico y de inmunohistoquímica es obligatorio para realizar el diagnóstico, y es necesario descartar su origen en otro sitio del cuerpo. Informamos el caso de un linfoma no Hodgkin primario de apéndice, con sus hallazgos clínicos, histopatológicos y de inmunohistoquímica, en una mujer de 36 años(AU)

Primary lymphomas of the appendix are rare malignancies that may present as acute appendicitis. Histopathology and immunohistochemistry are indispensable in order to exclude an origin elsewhere. We describe the clinical, histopathological and immunohistochemical characteristics of a case of primary appendix lymphoma in a 36 year old female(AU)

Mucinous cystadenoma of the pyelocaliceal system: a report of 3 examples and an analysis of 17 previously published cases.

We report 3 patients all men between 45 and 64 years of age with unilocular or multilocular mucinous cystadenomas of the kidney. One tumor arose from the renal pelvis, and 2 involved the entire pyelocaliceal system. The tumors measured between 2.4 and 37 cm in greatest dimension. Two patients were asymptomatic, and 1 had recurrent attack of acute pyelonephritis. Microscopically, the morphology and immunophenotype (CK20, MUC2, and CDX2 positive) of the tumors were similar to the colonic adenomas. Two patients were asymptomatic 24 and 64 months after surgery, including the patient with mucinous cystadenoma and intramucosal carcinoma. One patient died of acute myocardial infarction, and his tumor was an autopsy finding. Only 17 cases of mucinous cystadenomas and 5 cases of mucinous cystadenocarcinomas have been reported. Of the 17 mucinous cystadenomas, 2 arose in horseshoe kidneys. The mean size of these neoplasms was 15 cm (2.4-37 cm). Despite their large size, some patients with mucinous cystadenomas were asymptomatic. Sixty percent were associated with renal lithiasis. Thirty percent progressed to mucinous adenocarcinomas, and only 2 cases showed areas of intramucosal carcinomas. Two cases were associated with carcinoid tumors, similar to those reported in the appendix. Most patients were asymptomatic after surgery, and only 1 patient died by abdominal sepsis related to adenomucinosis. The 3 examples of mucinous cystadenomas of the pyelocaliceal system reported here, and those previously published indicate that they are very uncommon neoplasms with morphology and intestinal immunophenotype similar to the colonic adenomas.

Carcinoma de mama con células gigantes tipo osteoclasto. Informe de un caso de una variante rara / A rare variant of breast cancer with osteoclast-like giant cells. A case report

El carcinoma de mama con células gigantes tipo osteoclasto (CMCGO) es una variante distintiva y rara del carcinoma de mama, y se han reportado casos con patrones de crecimiento en casi todas los tipos de carcinoma mamario, siendo rara la presentación en los tumores bien diferenciados. Informamos un caso de carcinoma ductal infiltrante bien diferenciado con abundantes células gigantes tipo osteoclasto (CGO). Se realizaron reacciones de inmunohistoquímica para demostrar la diferencia inmunofenotípica de la neoplasia y de las CGO. Se hace una revisión de la literatura, ilustrando las características morfológicas, y se discuten los diagnósticos diferenciales(AU)

Breast carcinoma with osteoclast-like giant cells (BCOGC) is a rare, distinctive form of breast cancer. Although cases have been reported with many growth patterns in almost all types of breast cancer, being rarely found in well differentiated tumours. We report a case of well-differentiated ductal carcinoma with abundant osteoclast-like giant cells (OGC). Immunohistochemistry demonstrated the immunophenotypic differences of the tumour and the OGC. The literature is reviewed, illustrating the characteristic morphology and the differential diagnosis is discussed(AU)

Seudotumor hemofílico: complicación poco frecuente en pacientes con deficiencia del factor VIII y IX que asemeja sarcoma de partes blandas / Haemophilic pseudotumour: a rare complication of factor VIII and IX deficiency which can mimic soft tissue sarcoma. A case report and review of the literature

El seudotumor hemofílico es una complicación infrecuente en pacientes hemofílicos y es básicamente un hematoma encapsulado en diferentes estadios de organización, que muchas veces llega a confundirse clínica y radiográficamente como un sarcoma osteogénico o de tejidos blandos. Informamos el caso de un varón de 30 años con hemofilia A y diagnóstico de seudotumor hemofílico en miembro pélvico izquierdo con evolución de un año. Se realizó amputación supracondílea en su manejo multidisciplinario, así como un estudio inmunohistoquímico. Se revisó la literatura(AU)

A rare complication of haemophilia is haemophilic pseudotumour which is an encapsulated haematoma in different stages of organization. However, it often resembling osteogenic or soft tissue sarcoma, both clinically and radiologically. We report a case of a 30 year old male with haemophilia A and a one year history of haemophilic pseudotumour of the left leg. A multidisciplinary team was responsible for his management. A supracondylar amputation was performed and immunohistochemical studies were carried out. The literature was reviewed(AU)

Angiofibroma atípico de la amígdala palatina / Atypical angiofibroma of the palatine tonsil. A case report

Los angiofibromas extranasales son tumores benignos poco frecuentes que tienen características clínicas e histológicas diferentes a su contraparte nasal. Informamos un caso de angiofibroma atípico de la amígdala palatina, con sus hallazgos histopatológicos e inmunohistoquímicos, en un hombre de 60 años(AU)

Extranasal angiofibromas are rare benign tumours with different clinical and histological characteristics from their nasal counterparts. We describe a case of atypical angiofibroma of the palatine tonsil in a 60 years old man and discuss its characteristic histopathology and immunohistochemistry(AU)

Tumor mesenquimal fosfatúrico con rosetas gigantes: causa poco frecuente de osteomalacia oncogénica / Phosphaturic mesenchymal tumour with giant rosettes: a rare cause of oncogenic osteomalacia

El tumor mesenquimal fosfatúrico es una neoplasia rara que causa osteomalacia oncogénica por la fosfatonina FGF-23. Se describe el caso de una mujer que fue diagnosticada de osteomalacia oncogénica donde la tomografía computarizada reveló un tumor de tejidos blandos en el tórax. Una vez extirpado, fue identificado como tumor mesenquimal fosfatúrico tipo tejido conectivo mixto; se hizo revisión de la literatura y sus diagnósticos diferenciales. En este caso observamos rosetas gigantes, un hallazgo histológico no descrito antes(AU)

Phosphaturic mesenchymal tumour is a rare neoplasm which causes oncogenic osteomalacia due to the phosphatonin FGF-23. We report a case of a female patient crippled with oncogenic osteomalacia who was seen to have a soft tissue tumour of the thorax. The tumour was diagnosed as a phosphaturic mesenchymal tumour (mixed connective tissue variant). Giant rosettes were seen, a finding not previously reported. The differential diagnosis is discussed and the literature reviewed(AU)

Paraganglioma paravertebral maligno con metástasis óseas, pulmonares y en el sistema nervioso central / Malignant paravertebral paraganglioma with metastases in bone, lung and central nervous system. A case report

Se describe el caso de un varón de 40 años con dolor en hemitórax izquierdo. Inicialmente la neoplasia se extirpó de forma incompleta. Cuatro meses después, el paciente fue reintervenido por recidiva local y presentó metástasis en pulmón, una costilla y el sistema nervioso central. El estudio histopatológico mostró una proliferación celular con patrón de crecimiento zellballen y positividad para cromogranina, sinaptofisina y enolasa neuronal específica. El índice de proliferación (Ki-67) fue superior al 2%. El conjunto de datos confirmó el diagnóstico de paraganglioma maligno(AU)

A 40-year old man presenting with left sided chest pain, initially underwent surgery during which a tumour was partially removed. Four months later, he had a further surgical intervention to remove a local recurrence and metastases were found in the lung, a rib and the central nervous system. The biopsy showed cell proliferation with a zellballen growth pattern and positivity for chromogranin, synaptophysin and neuron-specific enolase. The proliferation index (Ki-67) was higher than 2%. These findings confirmed the diagnosis of malignant paraganglioma(AU)

Carcinoma neuroendocrino de células grandes de la próstata. Informe de autopsia de un caso inusual / Large cell neuroendocrine carcinoma of the prostate. A case report and review of the literature

Se presenta el caso de un hombre de 69 años de edad con antecedente de adenocarcinoma de próstata, el cual falleció por tromboembolia pulmonar. Se realizó estudio de autopsia, en el que se encontró un carcinoma neuroendocrino de células grandes de la próstata, que fue confirmado por inmunohistoquímica. Se hace una revisión de la literatura, ilustrando las características morfológicas de esta rara neoplasia(AU)

A case is presented of a 69-year-old man with a previous history of adenocarcinoma of the prostate who died of pulmonary embolism. Autopsy revealed a large cell neuroendocrine carcinoma of the prostate, which was confirmed by immunohistochemistry. The morphology and differential diagnosis of this rare tumour is discussed together with a review of the literature(AU)

Leiomiosarcoma de la vena cava inferior. Presentación de un caso y revisión del cuadro clinicopatológico / Leiomyosarcoma of the inferior vena cava. A case report and review of the clinical and pathological features

Se presenta el caso de un hombre de 63 años de edad con leiomiosarcoma de la vena cava inferior que falleció por síndrome de vena cava inferior secundario al tumor. Se realizó el estudio de autopsia donde se demuestra el sitio primario de la neoplasia, así como reacciones de inmunohistoquímica para confirmar su estirpe histológica. Se hace una revisión de la literatura, ilustrando las características morfológicas, y se discuten los diagnósticos diferenciales(AU)

We present a case of leiomyosarcoma of the inferior vena cava in a 63 year old man who subsequently died due to vena cava syndrome secondary to the tumour. Autopsy revealed the primary neoplasm, and immunohistochemistry confirmed the histological diagnosis. Morphology and differential diagnosis are discussed together with a review of the literature(AU)