A fundamental question in cancer biology is whether cells with tumorigenic potential are common or rare within human cancers. Studies on diverse cancers, including melanoma, have indicated that only ...rare human cancer cells (0.1-0.0001%) form tumours when transplanted into non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice. However, the extent to which NOD/SCID mice underestimate the frequency of tumorigenic human cancer cells has been uncertain. Here we show that modified xenotransplantation assay conditions, including the use of more highly immunocompromised NOD/SCID interleukin-2 receptor gamma chain null (Il2rg(-/-)) mice, can increase the detection of tumorigenic melanoma cells by several orders of magnitude. In limiting dilution assays, approximately 25% of unselected melanoma cells from 12 different patients, including cells from primary and metastatic melanomas obtained directly from patients, formed tumours under these more permissive conditions. In single-cell transplants, an average of 27% of unselected melanoma cells from four different patients formed tumours. Modifications to xenotransplantation assays can therefore dramatically increase the detectable frequency of tumorigenic cells, demonstrating that they are common in some human cancers.
Mucosal melanoma is a rare and poorly characterized subtype of human melanoma. Here we perform a cross-species analysis by sequencing tumor-germline pairs from 46 primary human muscosal, 65 primary ...canine oral and 28 primary equine melanoma cases from mucosal sites. Analysis of these data reveals recurrently mutated driver genes shared between species such as NRAS, FAT4, PTPRJ, TP53 and PTEN, and pathogenic germline alleles of BRCA1, BRCA2 and TP53. We identify a UV mutation signature in a small number of samples, including human cases from the lip and nasal mucosa. A cross-species comparative analysis of recurrent copy number alterations identifies several candidate drivers including MDM2, B2M, KNSTRN and BUB1B. Comparison of somatic mutations in recurrences and metastases to those in the primary tumor suggests pervasive intra-tumor heterogeneity. Collectively, these studies suggest a convergence of some genetic changes in mucosal melanomas between species but also distinctly different paths to tumorigenesis.
We investigated whether melanoma is hierarchically organized into phenotypically distinct subpopulations of tumorigenic and nontumorigenic cells or whether most melanoma cells retain tumorigenic ...capacity, irrespective of their phenotype. We found 28% of single melanoma cells obtained directly from patients formed tumors in NOD/SCID IL2Rγ
null mice. All stage II, III, and IV melanomas obtained directly from patients had common tumorigenic cells. All tumorigenic cells appeared to have unlimited tumorigenic capacity on serial transplantation. We were unable to find any large subpopulation of melanoma cells that lacked tumorigenic potential. None of 22 heterogeneously expressed markers, including CD271 and ABCB5, enriched tumorigenic cells. Some melanomas metastasized in mice, irrespective of whether they arose from CD271
− or CD271
+ cells. Many markers appeared to be reversibly expressed by tumorigenic melanoma cells.
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► Tumorigenic cells in melanomas from patients are common and phenotypically diverse ► Irrespective of their phenotype, many melanoma cells recapitulate tumor heterogeneity ► Melanoma cells exhibit phenotypic differences that are not hierarchically organized ► Heterogeneity arises from reversible phenotypic changes among tumorigenic cells
A Case of a Curious Skin Lesion Jordan, Ariel A.; Fullen, Douglas R.; Minhas, Deeba F.
Gastroenterology (New York, N.Y. 1943),
June 2023, 2023-06-00, 20230601, Volume:
164, Issue:
7
Journal Article
The genetic alterations contributing to melanoma pathogenesis are incompletely defined, and few independent prognostic features have been identified beyond the clinicopathological characteristics of ...the primary tumor. We used transcriptome profiling of 46 primary melanomas, 12 melanoma metastases, and 16 normal skin (N) samples to find genes associated with melanoma development and progression. Results were confirmed using immunohistochemistry and real-time PCR and replicated in an independent set of 330 melanomas using AQUA analysis of tissue microarray (TMA). Transcriptome profiling revealed that transcription factor HMGA2, previously unrecognized in melanoma pathogenesis, is significantly upregulated in primary melanoma and metastases (P-values=1.2 × 10−7 and 9 × 10−5) compared with N. HMGA2 overexpression is associated with BRAF/NRAS mutations (P=0.0002). Cox proportional hazard regression model and log-rank test showed that HMGA2 is independently associated with disease-free survival (hazard ratio (HR)=6.3, 95% confidence interval (CI)=1.8–22.3, P=0.004), overall survival (OS) (stratified log-rank P=0.008), and distant metastases–free survival (HR=6.4, 95% CI=1.4–29.7, P=0.018) after adjusting for American Joint Committee on Cancer (AJCC) stage and age at diagnosis. Survival analysis in an independent replication TMA of 330 melanomas confirmed the association of HMGA2 expression with OS (P=0.0211). Our study implicates HMGA2 in melanoma progression and demonstrates that HMGA2 overexpression can serve as an independent predictor of survival in melanoma.
Spitzoid melanocytic lesions encompass a spectrum from benign Spitz nevi to malignant spitzoid melanomas. Spitzoid melanocytic neoplasms have significant morphologic and molecular differences from ...conventional melanocytic lesions, and prediction of biologic behavior and metastatic risk may be difficult. Most challenging is the atypical Spitz tumor, a borderline spitzoid melanocytic lesion of uncertain malignant potential that has overlapping histologic features with conventional Spitz nevus and spitzoid melanoma. Atypical Spitz tumors involve the sentinel lymph nodes at a greater frequency than conventional melanoma and frequently harbor chromosomal copy number changes, yet most cases follow an indolent course. Herein we review the clinical, microscopic, and molecular features of atypical Spitz tumors, including recent molecular advances, including the potential prognostic significance of chromosomal abnormalities, such as homozygous CDKN2A loss.
Merkel cell carcinoma is a rare but highly aggressive cutaneous neuroendocrine carcinoma. Cytokeratin 20 (CK20) is expressed in ~95% of Merkel cell carcinomas and is useful for distinction from ...morphologically similar entities including metastatic small-cell lung carcinoma. Lack of CK20 expression may make diagnosis of Merkel cell carcinoma more challenging, and has unknown biological significance. Approximately 80% of CK20-positive Merkel cell carcinomas are associated with the oncogenic Merkel cell polyomavirus. Merkel cell carcinomas lacking Merkel cell polyomavirus display distinct genetic changes from Merkel cell polyomavirus-positive Merkel cell carcinoma, including RB1 inactivating mutations. Unlike CK20-positive Merkel cell carcinoma, the majority of CK20-negative Merkel cell carcinomas are Merkel cell polyomavirus-negative, suggesting CK20-negative Merkel cell carcinomas predominantly arise through virus-independent pathway(s) and may harbor additional genetic differences from conventional Merkel cell carcinoma. Hence, we analyzed 15 CK20-negative Merkel cell carcinoma tumors (10 Merkel cell polyomavirus-negative, four Merkel cell polyomavirus-positive, and one undetermined) using the Ion Ampliseq Comprehensive Cancer Panel, which assesses copy number alterations and mutations in 409 cancer-relevant genes. Twelve tumors displayed prioritized high-level chromosomal gains or losses (average 1.9 per tumor). Non-synonymous high-confidence somatic mutations were detected in 14 tumors (average 11.9 per tumor). Assessing all somatic coding mutations, an ultraviolet-signature mutational profile was present, and more prevalent in Merkel cell polyomavirus-negative tumors. Recurrent deleterious tumor suppressor mutations affected TP53 (9/15, 60%), RB1 (3/15, 20%), and BAP1 (2/15, 13%). Oncogenic activating mutations included PIK3CA (3/15, 20%), AKT1 (1/15, 7%) and EZH2 (1/15, 7%). In conclusion, CK20-negative Merkel cell carcinoma display overlapping genetic changes with CK20-positive Merkel cell carcinoma, including RB1 mutations restricted to Merkel cell polyomavirus-negative tumors. However, some CK20-negative Merkel cell carcinomas harbor mutations not previously described in Merkel cell carcinoma. Hence, CK20-negative Merkel cell carcinomas harbor diverse oncogenic drivers which may represent therapeutic targets in individual tumors.
A 58‐year‐old woman was admitted for heart failure and concern for cardiogenic shock. The patient had been recently placed on colchicine and allopurinol, 4 months and 3 weeks, respectively, prior to ...admission. Upon admission, she had a cutaneous eruption that had started abruptly several days after allopurinol initiation. It included multiple erythematous papules with scant scale on the forearms and numerous erythematous papules on the legs. Because of the varied morphologic presentation, biopsies from both the thigh and forearm were performed for a suspected drug reaction. The specimen from the thigh showed a superficial‐dermal, band‐like lymphocytic infiltrate with dyskeratosis and numerous intraepidermal mitotic figures predominantly in metaphase. In addition, there were neutrophils with leukocytoclasia. The specimen from the forearm showed superficial perivascular lymphocytic inflammation and intraepidermal dyskeratosis with mitotic figures similar to the thigh biopsy specimen but without a dermal neutrophilic infiltrate. An unusual drug eruption with features of colchicine toxicity was favored. Colchicine toxicity is not a commonly encountered clinical scenario and cutaneous findings have only rarely been described. Herein we report an exceedingly rare case of an unusual drug reaction with “colchicine figures” (i.e., ring‐shaped mitotic figures arrested in metaphase) consistent with colchicine toxicity.
Diagnosis of calciphylaxis is crucial, yet its distinction from other vascular diseases can be challenging. Although vascular calcification and thrombosis are hallmarks of calciphylaxis, the ...incidence and patterns of these features in other vascular diseases have not been well characterized. The specificity of fine calcium deposits in vessel walls (identifiable on von Kossa VK stain only) and other extravascular calcifications is not entirely clear. We retrospectively examined the clinicopathologic features in calciphylaxis (n=27), gangrene and viable skin at amputation margin (n=20 each), chronic stasis (n=22), and thrombotic vasculopathy (n=19) to identify useful discriminators. Calcification of subcutaneous small vessels appreciable on hematoxylin and eosin stain was relatively specific for calciphylaxis, although sensitivity was low (56%). VK detected fine calcium deposits in vessel walls not appreciable on hematoxylin and eosin, however, specificity was limited by frequent finding of similar deposits in peripheral artery disease. Combining calcium deposits detected by VK and thrombosis of subcutaneous small vessels resulted in optimal sensitivity (85%) and specificity (88%) for calciphylaxis. Similar observations applied to medium-sized vessel calcification. Calcification of eccrine gland basement membranes, elastic fibers, and perineurium did not effectively distinguish calciphylaxis from other groups. Diffuse dermal angiomatosis was exclusively found in calciphylaxis in this study. In conclusion, VK is useful in enhancing the detection of vascular calcification and avoiding the false-negative diagnosis, but this finding requires concomitant subcutaneous small vessel thrombosis to support a diagnosis of calciphylaxis. Diffuse dermal angiomatosis should increase suspicion for underlying calciphylaxis and prompt deeper sampling in the appropriate clinical setting.
Abstract Porocarcinomas are a rare eccrine carcinoma with significant metastatic potential. Oncogenic drivers of porocarcinomas have been underexplored, with PIK3CA activating mutation reported in ...one case. We analyzed 5 porocarcinomas by next generation sequencing using the DNA component of the Oncomine Comprehensive Assay (OCP), which provides data on copy number changes and mutational events in 126 cancer-relevant genes through multiplex PCR. We detected an average of 3.3 high-confidence nonsynonymous mutations per tumor (range: 1-6), including a spectrum of oncogenic activation and tumor suppressor inactivation events. Tumor suppressor mutations included TP53 (4/5, 80%), RB1 (3/5, 60%), ATM (2/5, 40%), ARID1A (1/5, 20%) and CDKN2A (1/5, 20%). In 4/5 (80%) tumors, at least one potential oncogenic driver was identified. Activating HRAS mutations were detected in 2/5 (40%), including G13D and Q61L hotspot mutations. Mutations of EGFR were identified in 2/5 (40%); these mutations have been previously reported in cancer but did not affect classic activation hotspot sites. EGFR and HRAS mutations were mutually exclusive. HRAS mutations were detected by targeted sequencing in a minority of benign eccrine poromas (2/17, 11.7%), suggesting HRAS activation may rarely be an early event in sweat gland neoplasia. Together, our data suggest roles for HRAS and EGFR as drivers in a subset of poroma and porocarcinoma. TP53 and RB1 inactivation events are also likely to contribute to tumorigenesis. These findings suggest that porocarcinomas display diversity with respect to oncogenic drivers, which may have implications for targeted therapy in metastatic or unresectable cases.
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