An Unusual Gingival (Peripheral) Tumor with Features of Keratoameloblastoma with Cytologic Atypia or Possible Malignant Transformation Exhibiting ARID1A Mutation.

BACKGROUND: Keratoameloblastoma is a poorly characterized and rarely reported odontogenic neoplasm that can exhibit overlapping histopathologic features with conventional ameloblastoma and keratocystic odontogenic tumor (KCOT), with an ambiguous relationship to the so-called solid KCOT. METHODS: A peripheral maxillary tumor causing bone saucerization in a 54-year-old male is described and investigated with immunohistochemistry and Next-Generation Sequencing (NGS). RESULTS: Microscopically, the tumor comprised of a predominantly plexiform proliferation of odontogenic epithelium with central keratinization and evidence of surface origin. Peripheral cells exhibited nuclear palisading with variable reverse polarization, while stellate reticulum-like areas were observed internally. A few follicles and a few foci in the lining of cystic spaces revealed increased cellularity with cells exhibiting small but conspicuous nucleoli, focal nuclear hyperchromatism, and a few mitoses mostly seen in the peripheral outer cell layer. Nuclear staining for ki-67 was increased in those areas when compared with the other cystic, follicular, and plexiform areas. These features were interpreted as cytologic atypia suggesting also the possibility of a malignant process. Immunohistochemically, the tumor was positive for CK19 and negative for BRAF VE1, calretinin, and CD56. Ber-Ep4 was only focally positive. By sequencing, an ARID1A c.6527_6538delAG frameshift mutation (VAF: 5.8%), classified as likely oncogenic, and an FBXW7 c.1627 A > G missense mutation (VAF: 8.0%), classified as a variant of uncertain significance, were detected. Two mutations, probably germline (VAF ~ 50%), were recorded for RNF43 and FBXW7. No pathogenic variants were identified in PTCH1, BRAF, NRAS, HRAS, KRAS, FGFR2, or SMO genes. CONCLUSION: The significance of an ARID1A variant in keratoameloblastoma is uncertain since this variant has not been reported in ameloblastoma or KCOT, to date. Alternatively, it may characterize malignant transformation in the present case since ARID1A mutations have been encountered in various cancers. Sequencing of additional cases is necessary to determine whether this may represent a recurrent genomic event.

Primary mucosal melanomas of the head and neck are characterised by overexpression of the DNA mutating enzyme APOBEC3B.

AIMS: Primary head/neck mucosal melanomas (MMs) are rare and exhibit aggressive biologic behaviour and elevated mutational loads. The molecular mechanisms responsible for high genomic instability observed in head/neck MMs remain elusive. The DNA cytosine deaminase APOBEC3B (A3B) constitutes a major endogenous source of mutation in human cancer. A3B-related mutations are identified through C-to-T/-G base substitutions in 5'-TCA/T motifs. Herein, we present immunohistochemical and genomic data supportive of a role for A3B in head/neck MMs. METHODS AND RESULTS: A3B protein levels were assessed in oral (n = 13) and sinonasal (n = 13) melanomas, and oral melanocytic nevi (n = 13) by immunohistochemistry using a custom rabbit α-A3B mAb (5210-87-13). Heterogeneous, selective-to-diffuse, nuclear only, A3B immunopositivity was observed in 12 of 13 (92.3%) oral melanomas (H-score range = 9-72, median = 40) and 8 of 13 (62%) sinonasal melanomas (H-score range = 1-110, median = 24). Two cases negative for A3B showed prominent cytoplasmic staining consistent with A3G. A3B protein levels were significantly higher in oral and sinonasal MMs than intraoral melanocytic nevi (P < 0.0001 and P = 0.0022, respectively), which were A3B-negative (H-score range = 1-8, median = 4). A3B levels, however, did not differ significantly between oral and sinonasal tumours (P > 0.99). NGS performed in 10 sinonasal MMs revealed missense NRAS mutations in 50% of the studied cases and one each KIT and HRAS mutations. Publicly available whole-genome sequencing (WGS) data disclosed that the number of C-to-T mutations and APOBEC3 enrichment score were markedly elevated in head/neck MMs (n = 2). CONCLUSION: The above data strongly indicate a possible role for the mutagenic enzyme A3B in head/neck melanomagenesis, but not benign melanocytic neoplasms.

Management of small testicular masses: outcomes from a single-centre specialist multidisciplinary team.

OBJECTIVES: To report the management outcomes of men with ≤20-mm small testicular masses (STMs) and to identify clinical and histopathological factors associated with malignancy. PATIENTS AND METHODS: A retrospective analysis of men managed at a single centre between January 2010 and December 2020 with a STM ≤20 mm in size was performed. RESULTS: Overall, 307 men with a median (interquartile range [IQR]) age of 36 (30-44) years were included. Of these, 161 (52.4%), 82 (26.7%), 62 (20.2%) and 2 men (0.7%) underwent surveillance with interval ultrasonography (USS), primary excisional testicular biopsy (TBx) or primary radical orchidectomy (RO), or were discharged, respectively. The median (IQR) surveillance duration was 6 (3-18) months. The majority of men who underwent surveillance had lesions <5 mm (59.0%) and no lesion vascularity (67.1%) on USS. Thirty-three (20.5%) men undergoing surveillance had a TBx based on changes on interval USS or patient choice; seven (21.2%) were found to be malignant. The overall rate of malignancy in the surveillance cohort was 4.3%. The majority of men who underwent primary RO had lesions ≥10 mm (85.5%) and the presence of vascularity (61.7%) on USS. Nineteen men (23.2%) who underwent primary TBx (median lesion size 6 mm) had a malignancy confirmed on biopsy and underwent RO. A total of 88 men (28.7%) underwent RO, and malignancy was confirmed in 73 (83.0%) of them. The overall malignancy rate in the whole STM cohort was 23.8%. Malignant RO specimens had significantly larger lesion sizes (median [IQR] 11 [8-15] mm, vs benign: median [IQR] 8 [5-10] mm; P = 0.04). CONCLUSIONS: Small testicular masses can be stratified and managed based on lesion size and USS features. The overall malignancy rate in men with an STM was 23.8% (4.3% in the surveillance group). Surveillance should be considered in lesions <10 mm in size, with a TBx or frozen-section examination offered prior to RO in order to preserve testicular function.

Metastatic Tumors to the Oral Soft Tissues and Jawbones: A Retrospective Analysis of 40 Cases and Review of the Literature.

BACKGROUND: Metastasis to the oral soft tissues and jawbones is rare and frequently associated with wide spread disease and dismal prognosis. Herein, we report the clinicopathologic characteristics of 40 intraoral metastatic neoplasms and perform a comprehensive review of the pertinent literature. METHODS: Criteria for inclusion included: (a) archived cases from the UMN Oral Pathology laboratory with available tissue blocks and/or H&E-stained preparations diagnosed between 2003 and 2021, (b) proper documentation of the clinico-radiographic characteristics of oral metastasis along with confirmed history of primary malignancy, or (c) microscopic findings consistent with metastatic disease with or without discovery of the primary site. RESULTS: Intraoral metastases comprised 0.03% of all accessioned cases; 22 (55%) occurred in men and 18 (45%) in women (median age = 66.5; range = 18-94 years). Eighteen cases (45%) involved the gingiva, 16 (40%) the gingiva and jawbones, 5 (12.5%) were exclusively intraosseous, and 1 affected (2.5%) the tongue. The lung was the two most frequent primary site in both men (n = 6, 27.3%) and women (n = 5, 27.7%), followed by the colon (n = 4, 18.2%) and kidney (n = 3, 13.7%) in men, and colon (n = 4, 22.2%) and breast (n = 3, 16.6%) in women. Analysis of 1,084 metastatic cases from the literature (male-to-female ratio = 1.2; mean = 52.3; range = 0.6-90 years) indicated strong preference for the jawbones (69.5%) and significant site-specific predilection of certain primary malignancies. CONCLUSIONS: Oral and gnathic metastases are rare but demonstrate a clear predilection for the gingiva and mandible. Clinicians should remain cognizant of such lesions since they frequently mimic inflammatory, reactive or benign neoplastic processes and, in certain cases, are the first indication of occult disease.

Self-regressing oral CD30-positive, EBV-negative, T-cell lymphoproliferative lesions. A poorly understood process highlighted by ominous clinicopathologic features and indolent behavior.

OBJECTIVE: Intraoral, primary, CD30-positive (CD30+) T-cell lymphoproliferative disorders (TLPDs) are uncommon, and their clinicopathologic presentation and management can vary and may be challenging. Herein, we present a retrospective study of 4 examples of self-regressing primary CD30+ TLPD affecting the gingiva. STUDY DESIGN: Archived files were retrospectively reviewed for oral CD30+ TLPDs featuring (1) proper immunohistochemical documentation, (2) Epstein-Barr virus negativity, (3) adequate follow-up information corroborating regression, and (4) no history of hematopoietic malignancy or related-mucocutaneous disease. RESULTS: Three women and 1 man (age range, 55-82 years; mean, 68.3 years) presented with rapidly growing gingival ulcers. Microscopic evaluation revealed diffuse infiltration by sheets of large, atypical cells admixed with lymphocytes and eosinophils, showing angiocentric distribution, focal neurotropism, and muscle infiltration. The lesional cells consistently stained for CD3 and CD30 and were variably immunoreactive against CD2, CD4, CD5, CD7, and CD8, but were negative for ALK1 and EBV-encoded small RNA. TCR-γ gene rearrangement studies revealed a monoclonal T-cell population in 1 case. All lesions showed complete regression 2 to 8 weeks postoperatively (mean follow-up, 4.5 weeks). CONCLUSIONS: Notwithstanding their alarming clinicopathologic appearance, there are CD30+ TLPDs confined to the oral cavity that have an indolent course. However, clinical staging is essential to exclude aggressive systemic malignancy.

Pale (Clear) Cell Acanthoma of the Palate.

Clear cell acanthoma (CCA), also known as pale cell acanthoma, represents a rare benign epidermal tumor with strong predilection for the lower extremities of middle-aged individuals and no frank gender preference. The etiology of CCA is poorly understood, although a localized psoriasiform reaction is favored. Herein, we report on the clinicopathologic and immunohistochemical features, and HPV status of an apparent example of oral CCA. A 58-year-old female presented with a well-circumscribed, asymptomatic, exophytic, sessile and erythematous nodule of the right hard palate, measuring 0.7 cm in greatest dimension. Microscopically, the lesion featured parakeratosis and acanthosis with neutrophilic microabscesses and broad elongated rete pegs. In areas, spinous epithelial cells exhibited pale or clear cytoplasm without nuclear pleomorphism, mitoses or cytologic atypia. The supporting connective tissue revealed mild chronic inflammation with few scattered neutrophils and numerous capillary vessels. PAS histochemical stain with and without diastase disclosed the presence of cytoplasmic glycogen in the pale cells. The majority of glycogen-rich epithelial cells stained strongly for EMA and were negative for D2-40. Ki-67 immunostaining was confined only to the basal cell layer of the epithelium. A diagnosis of CCA was rendered. The lesion was negative for human papillomavirus (HPV) infection, as assessed by HPV-DNA PCR using the MY09/11 primers for the L1 conserved region, thus HPV infection does not appear to contribute to the pathogenesis of oral CCA. In conclusion, we report an intraoral example of CCA in order to raise awareness about this entity.

Multiregion ultra-deep sequencing reveals early intermixing and variable levels of intratumoral heterogeneity in colorectal cancer.

Intratumor heterogeneity (ITH) contributes to cancer progression and chemoresistance. We sought to comprehensively describe ITH of somatic mutations, copy number, and transcriptomic alterations involving clinically and biologically relevant gene pathways in colorectal cancer (CRC). We performed multiregion, high-depth (384× on average) sequencing of 799 cancer-associated genes in 24 spatially separated primary tumor and nonmalignant tissues from four treatment-naïve CRC patients. We then used ultra-deep sequencing (17 075× on average) to accurately verify the presence or absence of identified somatic mutations in each sector. We also digitally measured gene expression and copy number alterations using NanoString assays. We identified the subclonal point mutations and determined the mutational timing and phylogenetic relationships among spatially separated sectors of each tumor. Truncal mutations, those shared by all sectors in the tumor, affected the well-described driver genes such as APC, TP53, and KRAS. With sequencing at 17 075×, we found that mutations first detected at a sequencing depth of 384× were in fact more widely shared among sectors than originally assessed. Interestingly, ultra-deep sequencing also revealed some mutations that were present in all spatially dispersed sectors, but at subclonal levels. Ultra-high-depth validation sequencing, copy number analysis, and gene expression profiling provided a comprehensive and accurate genomic landscape of spatial heterogeneity in CRC. Ultra-deep sequencing allowed more sensitive detection of somatic mutations and a more accurate assessment of ITH. By detecting the subclonal mutations with ultra-deep sequencing, we traced the genomic histories of each tumor and the relative timing of mutational events. We found evidence of early mixing, in which the subclonal ancestral mutations intermixed across the sectors before the acquisition of subsequent nontruncal mutations. Our findings also indicate that different CRC patients display markedly variable ITH, suggesting that each patient's tumor possesses a unique genomic history and spatial organization.

High-depth sequencing of over 750 genes supports linear progression of primary tumors and metastases in most patients with liver-limited metastatic colorectal cancer.

BACKGROUND: Colorectal cancer with metastases limited to the liver (liver-limited mCRC) is a distinct clinical subset characterized by possible cure with surgery. We performed high-depth sequencing of over 750 cancer-associated genes and copy number profiling in matched primary, metastasis and normal tissues to characterize genomic progression in 18 patients with liver-limited mCRC. RESULTS: High depth Illumina sequencing and use of three different variant callers enable comprehensive and accurate identification of somatic variants down to 2.5% variant allele frequency. We identify a median of 11 somatic single nucleotide variants (SNVs) per tumor. Across patients, a median of 79.3% of somatic SNVs present in the primary are present in the metastasis and 81.7% of all alterations present in the metastasis are present in the primary. Private alterations are found at lower allele frequencies; a different mutational signature characterized shared and private variants, suggesting distinct mutational processes. Using B-allele frequencies of heterozygous germline SNPs and copy number profiling, we find that broad regions of allelic imbalance and focal copy number changes, respectively, are generally shared between the primary tumor and metastasis. CONCLUSIONS: Our analyses point to high genomic concordance of primary tumor and metastasis, with a thick common trunk and smaller genomic branches in general support of the linear progression model in most patients with liver-limited mCRC. More extensive studies are warranted to further characterize genomic progression in this important clinical population.