American Journal of Surgical Pathology最新文献

A distinctive form of lung adenocarcinoma that closely mimics large-cell neuroendocrine carcinoma is described. The tumors arose in 6 women and 6 men aged 46-86 years (mean=58.4). They presented as peripheral subpleural masses measuring 2-12 cm (mean=6.5 cm). Histologically they were characterized by islands or anastomosing and serpiginous strands of large, atypical cells showing striking peripheral palisading of nuclei, with high mitotic activity and prominent comedo-like areas of necrosis. Because of the striking resemblance to neuroendocrine tumors, some of the cases were initially diagnosed as large-cell neuroendocrine carcinoma despite the absence of neuroendocrine markers. Immunohistochemistry showed positivity of the tumor cells for TTF1 and napsin-A, and negative staining for p40. The tumors were also uniformly negative for multiple neuroendocrine markers, including chromogranin, synaptophysin, CD56, and INSM1. Electron microscopy performed in 2 cases was negative for membrane-bound dense core neurosecretory granules. Pathogenic alterations were detected in 5 of 8 tumors tested by next-generation sequencing. Point mutations in KRAS and TP53 were identified in 5 patients. Low-level amplification of GNAS , KIT , and FGFR1 was present in 2 patients. No RB1 mutations were identified. Clinical follow-up in 10 cases showed that 2 patients died of their tumors, 2 experienced distant metastases, and 6 were alive and well from 1 to 13 years after diagnosis (median=7.1 y). Large-cell basaloid adenocarcinoma is an unusual variant of lung cancer that is easily confused with large-cell neuroendocrine carcinoma. Awareness of this unusual variant of lung adenocarcinoma is important for treatment and prognosis and for avoiding misdiagnosis.

A subset of desmoplastic melanomas (DMs) can show extensive morphologic and immunohistochemical overlap with cutaneous diffuse-type neurofibroma. Neurofibroma-like desmoplastic melanoma (NFLDM) thus poses a significant diagnostic pitfall because the clinical implications of these 2 entities differ dramatically. A series of 17 DMs, including 5 cases of NFLDM, were compared with a cohort of 53 cutaneous diffuse-type neurofibromas to explore the utility of molecular testing in the differential diagnosis between NFLDM and neurofibroma and to determine potentially useful morphologic features in this differential diagnosis. Unlike NFLDM, cutaneous diffuse-type neurofibromas: (1) rarely feature intratumoral or peritumoral lymphoid aggregates, (2) consistently harbor an intrinsic stromal support vasculature composed of evenly spaced capillary-sized vessels, and (3) infiltrate adjacent adipose tissue in a dermatofibrosarcoma protuberans-like manner with a complete lack of chronic inflammation or fat necrosis at the leading edge of the tumor. Conversely, DMs, including NFLDM: (1) do not contain Wagner-Meissner bodies, (2) often induce fat necrosis and/or chronic inflammation at the interface with adjacent fibroadipose tissue, (3) lack the intrinsic capillary-sized stromal vasculature observed in most neurofibromas, and (4) may harbor foci of perineuriomatous differentiation, mimicking a hybrid nerve sheath tumor. Any deviation from the expected clinical or morphologic features of cutaneous diffuse-type neurofibroma should raise suspicion for NFLDM. Although not entirely sensitive or specific, molecular testing can help to support the diagnosis of NFLDM by demonstrating genetic abnormalities associated with melanoma, including a UV-light-induced mutational signature, high tumor mutational burden, and/or chromosomal copy number alterations typical of melanoma.

Sialadenoma papilliferum is a tumor characterized by surface papillary projections and glandular/microcystic proliferation at the lesion base. Cases in which surface involvement is absent have been termed "sialadenoma papilliferum-like intraductal papillary tumor." Similar tumors that are present in the mandible have been termed "tubulopapillary hidradenoma-like tumor of the mandible." While previously considered benign, these tumors demonstrate variable clinical behavior and likely exist on a spectrum, rather than as discrete entities. In this study, we present a detailed clinicopathologic and molecular analysis of these lesions and propose a unifying diagnostic term: sialadenopapillary ductal tumor (SDT). Twenty-two cases with similar histologic features were reviewed, with special attention being paid to the clinicopathologic features. Immunohistochemistry for BRAF V600E and molecular testing were performed where material was available. The cases had varying diagnoses, ranging from benign to malignant. Six cases involved bone, 1 of which metastasized to a local lymph node. Of the 20 cases tested for BRAF V600E by immunohistochemistry, 18 were positive. Molecular testing was performed in 5 cases, where BRAF, PTPN11, and PIK3CA mutations were identified, predominantly members of the RAS-RAF-MEK-ERK pathway. In addition, 1 case was reclassified as an intraductal carcinoma after the identification of an NCOA4::RET gene fusion. Tumors on the SDT spectrum all share morphologic and molecular commonalities with unreliable distinguishing features. These tumors demonstrate the potential for aggressive local growth and regional metastasis. We propose a unifying diagnostic term for these lesions to reflect their common morphologic and molecular features and, most importantly, low malignant potential.

The aim of the study was to report the outcome of primary localized low-grade fibromyxoid sarcoma (LGFMS), sclerosing epithelioid fibrosarcoma (SEF), and hybrid LGFMS/SEF (H-LGFMS/SEF). Patients with primary localized LGFMS, SEF, or H-LGFMS/SEF, surgically treated with curative intent from January 2000 to September 2022, were enrolled from 14 countries and 27 institutions. Pathologic inclusion criteria were predefined by expert pathologists. The primary endpoint was overall survival (OS). Secondary endpoints were crude cumulative incidence (CCI) of local recurrence (LR), CCI of distant metastases (DM), and post-metastases OS (p-OS). Two hundred ninety-four patients (239 LGFMS, 32 SEF, and 23 H-LGFMS/SEF) were identified. At a median(m-) follow-up (FU) of 57.1 months, 12/294 patients died. The 5- and 10-year OS were 99.0% and 95.9% in LGFMS, 86.2% and 67.0% in SEF, and 84.8% and 84.8% in H-LGFMS/SEF, respectively. Predictors of worse OS included pathology, age at surgery, systemic therapy, and radiotherapy. LR developed in 13/294 (4.4%) patients. The observed m-time to LR was 10.7 months. The 5- and 10-yr CCI-LR were 4.7% in LGFMS and 6.6% in SEF, respectively. There were no LR events in H-LGFMS/SEF. The sole predictor of higher risk of LR was histology. DM developed in 23/294 (7.8%) patients. The observed m-time to DM was 28.2 months. The 5- and 10-yr CCI-DM were 1.3% and 2.7% in LGMFS, 29.9% and 57.7% in SEF, 48.9% and 48.9% in H-LGFMS/SEF, respectively. Predictors of higher risk of DM were histology, systemic therapy, and radiotherapy. Primary localized LGFMS treated with complete surgical resection has an excellent prognosis, while about 50% of H-LGFMS/SEF and SEF develop DM within 5 to 10 years. Very long-term FU is needed to understand absolute cure rates.

Pulmonary sclerosing pneumocytoma (PSP) is a rare neoplasm with indolent clinical behavior and usually presents as a solitary nodule, while only a few cases involving multiple nodules. Recent studies have revealed frequent AKT1 mutations in PSP; however, the molecular genetics of multiple PSPs remain unclear. To better understand the genetic background, eleven patients (4.2%, 11/260) with multiple PSP nodules were identified, and whole-exome sequencing (WES) was performed on 6 patients. Among 5 patients with 2 or 3 PSP nodules, AKT1 alterations were the most common (50%, 7/14), and the predominant alteration was p.E17K (21.4%, 3/14). Novel ARID1A mutations were the second most common driver (14.3%, 2/14), and we first identified these mutations cooccurred with AKT1 p.E17K mutation. Moreover, we observed limited concordance in the mutation spectra and few comutated genes among different lesions from these 5 patients, indicating that PSP with 2 or 3 nodules were independent arising tumors. No AKT1 mutations were identified in 3 PSP samples from a patient with multiple diffuse nodules. However, there were 17 shared genetic alterations among the 3 lesions, but none were typical driver mutations. The findings on multiple diffuse PSP nodules may also have independent origins, but the potential that some of these nodules are metastatic nodules cannot be excluded. In conclusion, this retrospective study is the largest series of multiple PSP cases and provides new insights into the genomic underpinning of PSP. This work has a potential to broaden our understanding of the pathogenesis and development of these lesions and warrants analysis in larger cohorts.

Synovial sarcoma (SS) is a rare genitourinary malignancy with a specific SS18::SSX 1/2 gene fusion in majority of the instances. The paratesticular location of this neoplasm is extremely rare and only 4 cases are reported in the literature. Herein, we describe the clinicopathologic features and molecular profile of paratesticular SS in the largest case series to date and to the best of our knowledge, and the only series to use novel SS18-SSX antibody for immunohistochemistry. Clinicopathologic, immunohistochemical (IHC), molecular, treatment, and follow-up data of the patients were analyzed. There were 14 patients, ranging from 15 to 47 years (mean: 30 y). The tumor size ranged from 4​​​​​​ to 15 cm. The tumors were unilateral, solid, and homogeneous tan-white with monomorphic spindle cell histology. All 14 tumors expressed SS18-SSX and TLE1 IHC and harbored SS18 rearrangement. In addition, the tumor with multifocal SS18-SSX expression had lower break-apart signals in the FISH assay (38% of the tumor cells; range: 29% to 85%). Radical orchiectomy was performed in all 14 patients and adjuvant chemotherapy was administered in 9 patients. Follow-up was available in 9 patients. The follow-up duration ranged from 5 to 24 months (median=10 mo). Four patients died of metastatic disease (range: 5 to 16 mo) and 2 patients who are alive had metastatic disease at the last follow-up. Based on our experience with the largest series to date and aggregate of the published data, paratesticular SS has a poor prognosis despite aggressive therapy. Owing to its rarity, the differential diagnosis is wide and requires a systematic approach for ruling out key morphologic mimics aided with SS18-SSX IHC and molecular confirmation because this distinction carries important therapeutic and prognostic implications. Due to the excellent concordance of SS18-SSX IHC results with FISH results as observed in our study, we would like to suggest inclusion of SS18-SSX in the diagnostic immunohistochemistry panel of all spindle cell sarcomas where synovial sarcoma is considered as a morphologic differential. SS18-SSX-positive staining may be used as a surrogate for FISH assay in a resource-limited setting where molecular assay is not available. Furthermore, IHC has a fairly shorter turn-around-time, is less complex, and of low cost.

Low-grade nasopharyngeal papillary adenocarcinoma (LGNPPA) is a rare neoplasm originating from the surface mucosal epithelium in the nasopharynx. To clarify its clinicopathologic, immunohistochemical, and molecular features, we retrospectively enrolled 35 patients diagnosed with LGNPPA between May 2016 and March 2024. Our cohort consisted of 14 male and 21 female patients aged 11 to 71 years (median: 37 y). The most common symptoms were rhinorrhea and nasal obstruction. Most tumors originated from the roof of the nasopharynx and were clinically staged as T1N0M0. None of the patients had a history of thyroid tumors. Microscopically, most of the LGNPPA were composed of irregular papillary structures covered with single-layer columnar or cuboidal epithelium. Eighteen cases (18/35, 51.4%) showed squamous epithelium coverage, and 9 cases (9/35, 25.7%) showed the characteristic transformation of squamous epithelium into neoplasm. Squamous differentiation and a significant spindle cell component were noted in 9 cases (9/35, 25.7%) and 26 cases (26/35, 74.3%), respectively. All cases were positive for thyroid transcription factor-1 protein, CK7, EMA, and Galectin-3 but negative for thyroglobulin, PAX8, and Napsin A. Ki-67 labeling was low and ranged from 2% to 5%. The Epstein-Barr virus or human papilloma virus infection and BRAF V600E mutation were not detected in any of the cases. All patients underwent endoscopic surgical resection, and 4 patients received radiotherapy followed by endoscopic surgery. Complete follow-up data were available for 33 patients. All patients had no recurrent or metastatic disease in the last follow-up (3 to 88 mo). A definitive diagnosis depends on histopathology and immunohistochemistry studies. The optimal treatment for patients with LGNPPA is total excision. Given the extremely indolent biological behavior of LGNPPA, it may be more appropriate to classify it as a primary papillary epithelial tumor rather than an adenocarcinoma of the nasopharynx.

Ameloblastic fibroma (AF) and related lesions, namely ameloblastic fibrodentinoma (AFD) and ameloblastic fibro-odontoma (AFO), span a spectrum from true neoplasms to hamartomas. The 2017 World Health Organization classification proposes that AFD and AFO are precursors to odontomas, yet their precise nature remains uncertain. This study examined 19 AF cases, 4 AFD, 15 AFO, 19 odontomas (OD, 14 complex, 5 compound), and 2 ameloblastic fibrosarcomas (AFS), focusing on clinical characteristics, recurrence, and molecular profiles. AF primarily affected individuals under 20 years (60.0% of cases), mainly in the mandible (68.4%), with a recurrence rate of 21.1% in the followed cases. AFD and AFO appeared in younger patients (average age 15.7 y) without any recurrence observed. Notable differences in site and size distribution were observed between AF, its related lesions, and odontomas. Copy number alterations (CNAs) were detected in the mesenchymal component in 9 of 19 AF (47.4%), 2 of 4 AFD (50.0%), 6 of 14 AFO (42.9%), and 2 of 2 AFS (100%). In contrast, all odontomas exhibited normal CNAs, highlighting the specificity of CNAs in mesenchymal elements of AF and related lesions. BRAF p.V600E mutation was identified in the mesenchymal component in 13 of 19 AF (68.4%), 2 of 4 AFD (50.0%), 8 of 15 AFO (53.3%), and 2 of 2 AFS (100%), whereas all 19 odontomas were BRAF wild type. No mutations were found in the epithelial component. Our analysis reveals that AF and its related lesions present a spectrum of biological behaviors, from true neoplasms to hamartomas. The presence of BRAF p.V600E mutations and CNAs in their mesenchymal components, as opposed to odontomas, indicates potential neoplastic characteristics. Profiling copy number alterations in AF and related lesions emerge as a valuable tool for enhancing their differential diagnosis and facilitating the anticipation of disease progression. Our findings underscore the efficacy of copy number alteration analysis in determining the nature of lesions within AF and related lesions.

Clear cell adenocarcinoma (CCA) of the urinary tract is a rare malignancy and tumors involving the renal pelvis are notably sparse in the literature, with only 5 other patients reported. We present 5 patients, 4 women, and 1 man, with CCA of the renal pelvis. The age at presentation ranged from 29 to 81 years. The tumor size ranged from 4.5 to 8.0 cm. Tumors exhibited shared morphologic and immunohistochemical features with CCA of the female genital tract and those originating in the bladder and urethra, including cells with large nuclei, prominent nucleoli, nuclear hobnailing, and scant clear cytoplasm. Common immunohistochemical findings included reactivity for PAX8, CK7, HNF1β, and Napsin-A. One of the tumors arose in the background of a mixed epithelial and stromal tumor. Another tumor occurred in a renal allograft and tumor cells were positive for the BK virus, demonstrated by SV40 immunohistochemistry. All tumors were negative for TFE3 and TFEB rearrangement and lacked TERT alterations. Follow-up was limited with no recurrence in 4 patients at a maximum of 20 months follow-up and 1 patient died of an unrelated cause at 25 months of follow-up. Next-generation sequencing analysis of all 5 CCAs revealed mutations within genes implicated in DNA damage repair and chromatin remodeling pathways, including ATM, BRCA1, BRCA2, ARID1A, DICER1, SMAD4, NOTCH1, and MYC amplification. These molecular findings underscore the dysregulation of fundamental cellular processes essential for genomic integrity maintenance.

Pilomatrical skin tumors harbor mutations in CTNNB1, which encodes for β-catenin, a downstream effector of the Wnt signaling pathway responsible for the differentiation, proliferation, and adhesion of epithelial stem cells. Therefore, downstream molecules, such as CDX2, LEF-1, and SATB2, in the Wnt signaling pathway could be useful diagnostic markers. Here, we sought to investigate the potential of immunohistochemistry (IHC) to differentiate between pilomatricoma and pilomatrical carcinoma, as well as from other cutaneous adnexal tumors. We studied 88 cases of cutaneous tumors (14 pilomatrical carcinomas, 18 pilomatricomas, 13 basal cell carcinomas, 12 squamous cell carcinomas, 12 sebaceous carcinomas, 10 Merkel cell carcinomas, 7 trichoblastomas, and 2 hidradenocarcinomas) using a broad panel of IHC markers: β-catenin, SATB2, CDX2, LEF1, Ber-EP4, and PRAME. Pilomatricoma and pilomatrical carcinoma displayed >75% nuclear staining for β-catenin. CDX2 also strongly stained pilomatrical tumors; however, the staining distribution was limited in pilomatricoma and more widespread in pilomatrical carcinoma. But, overall, it was less than β-catenin. SATB2 and Ber-EP4 expressions were noted only in a subset of both pilomatrical carcinoma and pilomatricoma, whereas LEF-1 showed strong, diffuse nuclear positivity in both pilomatricoma and pilomatrical carcinoma. Among the IHC markers evaluated, none could distinguish between pilomatricoma and pilomatrical carcinoma. However, the combined use of β-catenin with CDX2 markers may assist in not only confirming the pilomatrical nature of the proliferation but also in differentiating benign from malignant cases when there is a significant presence of CDX2 staining. Despite these findings, the diagnosis should continue to primarily depend on a thorough histopathologic examination.