Correlation of histopathologic findings with clinical predictors of disease recurrence and progression to vulvar carcinoma in patients with differentiated vulvar intraepithelial neoplasia (dVIN).

Objective: To evaluate predictors of recurrence and the risk of progression to carcinoma in patients with dVIN. Methods: 36 self-identified White patients with dVIN from 2011 to 2022 were identified. Demographics, treatment and clinical course were abstracted. Histopathologic features and IHC stains were reviewed by 2 subspecialty pathologists. Standard statistical analyses were applied. Results: Median cohort age was 70 years (range 39-91). Median follow-up was 29.5 months (range 1-123). All patients were Caucasian. 67% had lichen sclerosus (LS) adjacent to dVIN. 56% of patients had recurrent dVIN a median of 11 months from diagnosis. 14 patients had invasive squamous cell carcinoma of the vulva (SCCV) during the study period: 9 (25%) with synchronous dVIN, 5 (14%) developed SCCV after a median of 21.5 months (range 8-57). Patients treated with surgery were more likely to have recurrent/persistent dVIN (p = 0.04) and synchronous or progression to SCCV (p = 0.02) than patients treated with topical therapy. Excluding 9 women with synchronous SCCV, no initial treatment (observation, topical therapy, surgery) was superior at preventing recurrent/ progressive disease in isolated dVIN. Mutation-type p53 expression was identified in 18 (64%) and aberrant GATA3 staining/expression in 20 (56%) of cases. Aberrant GATA3 expression was associated with a higher frequency of synchronous/progression to SCCV (p < 0.05). Conclusion: dVIN has an aggressive clinical course in white patients with a high risk of recurrence/persistence and synchronous/progression to SCCV despite treatment. Close surveillance with a low threshold for additional biopsies is warranted. P53 and GATA3 IHC stains may be useful markers of disease outcome.

Acute myeloid leukemia cutis with KMT2A::MLLT3 fusion presenting with leonine facies.

A 63-year-old woman presented with plaques covering 60 % body-surface-area and leonine facies. Blood work showed no diagnostic aberrancies. Skin biopsy contained a malignant CD4+/CD56+ mononuclear cell population concerning for blastic plasmacytoid dendritic cell neoplasm. A later bone marrow biopsy confirmed AML with KMT2A::MLLT10 fusion detected by next-generation sequencing (NGS). This patient's LC preceded blood and marrow based symptoms of AML. NGS of the initial skin biopsy should be considered as part of diagnostic guidelines in cases with LC in the differential as this may have led to earlier diagnosis in this case and future cases.

A novel method to assess copy number variations in melanocytic neoplasms: Droplet digital PCR for precise quantitation of MYC and MYB genes.

INTRODUCTION: While most melanocytic neoplasms can be classified as either benign or malignant by histopathology alone, ancillary molecular diagnostic tests can be necessary to establish the correct diagnosis in challenging cases. Currently, the detection of copy number variations (CNVs) by fluorescence in situ hybridization and chromosomal microarray (CMA) are the most popular methods, but remain expensive and inaccessible. We aim to develop a relatively inexpensive, fast, and accessible molecular assay to detect CNVs relevant to melanoma using droplet digital polymerase chain reaction (ddPCR) technology. METHODS: In this proof-of-concept study, we evaluated CNVs in MYC and MYB genes from 73 cases of benign nevi, borderline melanocytic lesions, and primary and metastatic melanoma at our institution from 2015 to 2022. A multiplexed ddPCR assay and CMA were performed on each sample, and the results were compared. RESULTS: Concordance analysis of ddPCR with CMA for quantification of MYC and MYB CNVs revealed a sensitivity and specificity of 89% and 86% for MYC and 83% and 74% for MYB, respectively. CONCLUSION: We demonstrate the first use of a multiplexed ddPCR assay to identify CNVs in melanocytic neoplasms. With further improvement and validation, ddPCR may represent a low-cost and rapid tool to aid in the diagnosis of histopathologically ambiguous melanocytic tumors.

Anti-PL-7, anti-Ro/SSA, anti-Mi-2, and anti-TIF1-γ correlate with specific patterns of histopathologic features in dermatomyositis: An analysis of 39 skin biopsy specimens from 25 patients.

BACKGROUND: In dermatomyositis (DM), myositis-specific and myositis-associated antibodies have been correlated with clinical features. It is unknown if histopathologic findings in lesional skin biopsies correlate with serologic subtypes of DM. METHODS: A retrospective chart review of patients with DM was performed. Patients with myositis antibodies and DM lesional skin biopsies were included in the study. Skin biopsies were reviewed by blinded dermatopathologists for 20 histopathologic features. RESULTS: There was a statistically significant (p < 0.05) association between anti-PL-7 serology and decreased degree of vacuolar degeneration, necrotic keratinocytes, and thickening of the epidermal basement membrane. Anti-aminoacyl tRNA synthetase (anti-ARS) antibodies had the same significant negative association with degree of vacuolar degeneration, necrotic keratinocytes, and thickening of the epidermal basement membrane. A similar pattern was seen with an anti-cytoplasmic serology; where there was a significant association with an increased degree of vacuolar degeneration and necrotic keratinocytes, and a nonsignificant trend of minimally thickened epidermal basement membrane. There was a statistically significant association between anti-Ro/SSA serology and increased degree of vacuolar degeneration. Anti-TIF1-γ serology was significantly associated with the increased presence of necrotic keratinocytes and pigment incontinence, and displayed a pattern of increased neutrophils. There was a significant association between anti-Mi-2 antibodies and pigment incontinence, as well as between myositis-specific antibodies and pigment incontinence. A statistically significant positive association was found between nuclear antibodies and degree of vacuolar degeneration, thickened epidermal basement membrane, pigment incontinence, and epidermal atrophy. CONCLUSION: In patients with DM, some specific serotypes, including anti-PL-7, anti-Ro/SSA, anti-Mi-2, and anti-TIF1-γ, may have characteristic histopathologic features.

PRAME expression in cutaneous melanoma does not correlate with disease-specific survival.

BACKGROUND: Immunohistochemistry-based protein biomarkers can provide useful prognostic information in cutaneous melanoma. The independent prognostic value of Ki-67 has been studied with variable results. PReferentially expressed Antigen in MElanoma (PRAME) immunohistochemistry is a useful new ancillary tool for distinguishing cutaneous nevi from melanoma; however, its prognostic value has not been well studied. We evaluated PRAME as a prognostic marker in cutaneous melanoma, compared to Ki-67. METHODS: We analyzed the immunohistochemical expression of PRAME and Ki-67 in 165 melanocytic lesions, including 92 primary melanomas, 19 metastatic melanomas, and 54 melanocytic nevi using tissue microarrays. PRAME immunostaining was scored based on the percentage of positive nuclei: 0 <1%, 1+ 1%-25%, 2+ 26%-50%, 3+ 51%-75%, and 4+ >75%. The percentage of Ki-67-positive tumor nuclei was used to calculate the proliferation index. RESULTS: PRAME and Ki-67 both showed significantly increased expression in melanomas compared to nevi (p < 0.0001 and p < 0.001, respectively). There was no significant difference in PRAME expression in primary versus metastatic melanomas. By contrast, the Ki-67 proliferation index was higher in metastatic melanoma than in primary melanoma (p = 0.013). Increased Ki-67 index correlated with ulceration (p < 0.001), increased Breslow depth (p = 0.001), and higher mitotic rate (p < 0.0001), whereas increased PRAME expression correlated with higher mitotic rate (p = 0.047) and Ki-67 index (p = 0.007). Increased Ki-67 index correlated with worse disease-specific survival in patients with primary melanoma (p < 0.001), but PRAME expression did not show prognostic significance in disease-specific survival (p = 0.63). In a multivariable analysis of patients with primary melanoma, tumor Breslow depth, ulceration, mitotic rate, and Ki-67 index were each independent predictors of disease-specific survival (p = 0.006, 0.02, 0.001, and 0.04, respectively); however, PRAME expression was not predictive of disease-specific survival (p = 0.64). CONCLUSION: Ki-67 is an independent prognostic marker; although increased PRAME expression correlates with the Ki-67 proliferation index and mitotic rate, PRAME is not an independent prognostic marker for cutaneous melanoma. PRAME and Ki-67 are useful ancillary tools for distinguishing benign from malignant melanocytic lesions.

A Novel Method to Detect Copy Number Variation in Melanoma: Droplet Digital PCR for Quantitation of the CDKN2A Gene, a Proof-of-Concept Study.

ABSTRACT: A definitive diagnosis of nevus or melanoma is not always possible for histologically ambiguous melanocytic neoplasms. In such cases, ancillary molecular testing can support a diagnosis of melanoma if certain chromosomal aberrations are detected. Current technologies for copy number variation (CNV) detection include chromosomal microarray analysis (CMA) and fluorescence in situ hybridization. Although CMA and fluorescence in situ hybridization are effective, their utilization can be limited by cost, turnaround time, and inaccessibility outside of large reference laboratories. Droplet digital polymerase chain reaction (ddPCR) is a rapid, automated, and relatively inexpensive technology for CNV detection. We investigated the ability of ddPCR to quantify CNV in cyclin-dependent kinase inhibitor 2A ( CDKN2A ), the most commonly deleted tumor suppressor gene in melanoma. CMA data were used as the gold standard. We analyzed 57 skin samples from 52 patients diagnosed with benign nevi, borderline lesions, primary melanomas, and metastatic melanomas. In a training cohort comprising 29 randomly selected samples, receiver operator characteristic curve analysis revealed an optimal ddPCR cutoff value of 1.73 for calling CDKN2A loss. In a validation cohort comprising the remaining 28 samples, ddPCR detected CDKN2A loss with a sensitivity and specificity of 94% and 90%, respectively. Significantly, ddPCR could also identify whether CDKN2A losses were monoallelic or biallelic. These pilot data suggest that ddPCR can detect CDKN2A deletions in melanocytic tumors with accuracy comparable with CMA. With further validation, ddPCR could provide an additional CNV assay to aid in the diagnosis of challenging melanocytic neoplasms.

Histiocytoid melanoma: Diagnostic pitfall and mimicker of non-Langerhans cell histiocytoses including reticulohistiocytoma.

Melanoma and benign histiocytic proliferations can sometimes show considerable clinical and histopathologic overlap. Recently, cases of melanomas resembling xanthogranuloma and Rosai-Dorfman disease have been reported, and herein we report a case of melanoma closely mimicking reticulohistiocytoma. An 84-year-old man presented with a 1 cm purple-red nodule on his arm concerning for squamous cell carcinoma. While the biopsy findings resembled reticulohistiocytoma, the clinical context and regression changes at the lesion perimeter raised stronger concern for melanoma, which was confirmed with immunohistochemistry. We review prior rare reports of melanomas resembling non-Langerhans cell histiocytic proliferations and summarize helpful clinical and histopathologic clues to avoid a diagnostic pitfall when confronted with this unusual quandary.

Primary cutaneous gamma-delta T-cell lymphoma masquerading as leukemia cutis in a patient recently diagnosed with small lymphocytic lymphoma: Clues to the diagnosis.

A 54-year-old man recently diagnosed with small lymphocytic lymphoma (SLL) had waxing and waning, indurated, erythematous plaques on his legs, with leukopenia and anemia disproportionate to the SLL burden in his marrow and pelvic lymph nodes. Punch biopsy of a plaque performed to evaluate for leukemia cutis revealed a lymphocytic lobular-panniculitis-like infiltrate resembling lupus panniculitis, but a preponderance of CD8+/Ki-67+ T-cells surrounding adipocytes raised concern for subcutaneous panniculitis-like T-cell lymphoma (SPTCL). Additional immunohistochemistry (IHC) studies showed that the adipotropic T-cells expressed TCR-gamma, supporting the rare, unexpected diagnosis of Primary cutaneous gamma-delta T-cell lymphoma (PCGDTCL). The patient subsequently met diagnostic criteria for hemophagocytic lymphohistiocytosis (HLH). PCGDTCL is an aggressive, HLH-associated lymphoma requiring different management than SPTCL and SLL. This case illustrates how PCGDTCL can co-exist with B-cell lymphoma and resemble panniculitis on biopsies. PCGDTCL and SPTCL should enter the differential diagnosis whenever patients present with the constellation of lobular panniculitis and unexplained cytopenias. In the present case, close clinicopathologic correlation and judicious use of IHC on a small sample allowed for a prompt diagnosis.

Molecular analysis of NUT-positive poromas and porocarcinomas identifies novel break points of YAP1::NUTM1 fusions.

BACKGROUND: Poromas, and their malignant counterparts, porocarcinomas, harbor recurrent translocations involving YAP1-MAML2, YAP1-NUTM1, and infrequently WWTR1-NUTM1; YAP1-NUTM1 being the most common in porocarcinomas. NUT immunohistochemistry (IHC) can be used to identify NUTM1-translocated tumors. This study sought to investigate potential novel NUTM1-fusion partners among NUT IHC-positive poromas and porocarcinomas. METHODS: Thirteen NUT IHC-positive poroid tumors (four poromas and nine porocarcinomas) were identified within a multi-institutional international cohort. Next-generation sequencing (NGS) assessed for NUTM1 fusion partners. RESULTS: NGS detected a NUTM1 fusion in 12 of 13 cases: YAP1-NUTM1 (11/12 cases) and WWTR1-NUTM1 (1/12 cases). Two of the cases (2/12) with NUTM1 fusion were not called by the NGS algorithm but had at least one read-spanning YAP1-NUTM1 break point upon manual review. A NUTM1 fusion was not identified in one case; however, the sample had low RNA quality. The following fusion events were identified: YAP1 exon 4::NUTM1 exon 3 in six cases, YAP1 exon 6::NUTM1 exon 2 in one case, YAP1 exon 3::NUTM1 exon 3 in three cases, WWTR1 exon 3::NUTM1 exon 3 in one case, and YAP1 exon 8::NUTM1 exon 3 fusion in one case. CONCLUSION: While no novel NUTM1 fusion partners were identified within our cohort, 12 of 13 cases had discoverable NUTM1 fusions; YAP1-NUTM1 fusion was detected in 11 cases (92%) and WWTR1-NUTM1 in 1 case (8%). These data corroborate findings from other recent investigations and further substantiate the utility of NUT IHC in diagnosing a subset of poroid neoplasms. In addition, two of our cases harbored fusions of YAP1 exon 6 to NUTM1 exon 3 and YAP1 exon 8 to NUTM1 exon 2, which have not been reported before in poroid neoplasms and indicate novel break points of YAP1.

PRAME immunohistochemistry is useful in the evaluation of conjunctival melanomas, nevi, and primary acquired melanosis.

BACKGROUND: Many dermatopathologists find conjunctival melanocytic proliferations challenging because they are rare relative to their cutaneous counterparts and have nuanced morphology and nomenclature. PRAME immunohistochemistry has been widely adopted for distinguishing cutaneous nevi from melanoma, but limited data exist assessing its utility in evaluating conjunctival specimens. In particular, it is uncertain whether it can predict the risk of melanoma progression in primary acquired melanosis (PAM). METHODS: Thirty clinically annotated cases (two melanomas, three PAM with atypia, seven PAM without atypia, 15 nevi, two combined nevi, and a diagnostically challenging nevus with atypical features) were retrospectively evaluated with PRAME. RESULTS: Strong, diffuse PRAME expression was present in melanomas and PAM with high-grade atypia, but not in PAM with low-grade atypia, PAM without atypia, or nevi. Scattered, faintly PRAME-positive intraepithelial melanocyte nuclei were identified in six nevi. A clonal nevus and nests of heavily pigmented type-A melanocytes in two additional nevi had cytoplasmic staining. CONCLUSIONS: PRAME was useful for distinguishing melanoma and its probable precursors from benign conjunctival melanocytic proliferations in our cohort. The data alert us to two diagnostic pitfalls in nevi: scattered, PRAME-positive intraepithelial melanocytes and cytoplasmic PRAME staining in type-A melanocytes and melanophages. Larger scale investigations are warranted to further substantiate these promising findings.

Comparison of adipophilin and recently introduced PReferentially expressed Antigen in MElanoma immunohistochemistry in the assessment of sebaceous neoplasms: A pilot study.

BACKGROUND: We and others have noticed consistent staining of sebaceous glands with PReferentially expressed Antigen in MElanoma (PRAME). We aimed to determine whether PRAME was as sensitive, specific, and interpretable as adipophilin for distinguishing sebaceous neoplasms (SNs) from other neoplasms. METHODS: Twenty SNs and 32 control cases were stained for PRAME and adipophilin. Extent of staining was scored as follows: 0, no staining; 1, <5% positivity; 2, 5% to 50% positivity; and 3, >50% positivity. Intensity was scored as negative, weak, moderate, or strong. A composite score was determined by adding the scores for extent and intensity. RESULTS: PRAME had positive composite scores in all 20 SNs in the more differentiated areas, whereas adipophilin had positive composite scores in 19/20 cases. PRAME showed positivity in the basaloid cells in 15/16 cases, whereas adipophilin was positive in 14. Among controls, PRAME and adipophilin had positive composite scores in 3/32 cases and 6/32 cases, respectively. CONCLUSIONS: PRAME and adipophilin are comparable in terms of distribution and intensity for staining sebocytes. In the basaloid cells, PRAME expression is often more diffuse and easier to detect than adipophilin. In comparing the SNs to the controls, PRAME was more sensitive and more specific than adipophilin. PRAME could be used as an additional marker of sebaceous differentiation in everyday practice.

Expanding Our Understanding of Nevogenesis: Copy Number Gain of Chromosome 15q in Melanocytic Nevi Is Associated With Distinct Histomorphologic Findings.

As the landscape of melanomagenesis becomes better refined through increasingly detailed schema grounded in distinct clinicopathologic-molecular pathways, the stepwise process and variations of molecular nevogenesis have largely remained elusive. Herein, we present a series of 8 melanocytic nevi in patients ranging from 40 to 74 years of age (median: 59.5 y), which demonstrated a reproducible constellation of histomorphologic features as well as a copy number gain of the long arm of chromosome 15 (15q). The most characteristic histologic feature was sclerosis with maturation at the base of the lesion. All cases demonstrated a dome-shaped configuration and epidermal acanthosis with hyperpigmentation. However, the cytologic features ranged in their appearances from that of a banal nevus with ovoid nuclei, inconspicuous nucleoli, and minimal cytoplasm to enlarged, epithelioid forms with central nucleoli and abundant cytoplasm. No lesions showed staining with BRAF V600E or NRAS Q61R immunohistochemistry. Single-nucleotide polymorphism-based chromosome microarray analysis revealed a monoaberrant 15q gain in all cases. The histology was sufficiently distinctive in the initial 6 cases encountered to allow for prospective identification of 2 additional cases harboring a 15q gain. The clinical follow-up did not reveal recurrence in any case. Although adverse outcomes were not observed in our cohort, future studies are needed to more adequately characterize the clinical and biological behavior of these lesions.

Comparative performance of insulinoma-associated protein 1 (INSM1) and routine immunohistochemical markers of neuroendocrine differentiation in the diagnosis of endocrine mucin-producing sweat gland carcinoma.

Endocrine mucin-producing sweat gland carcinoma (EMPSGC) is a rare cutaneous adnexal malignancy with predilection for the eyelids of older adults. It must be distinguished from metastatic adenocarcinomas of extracutaneous origin and from benign adnexal proliferations on partial samples when a solid growth component and mucin production are not evident. Thus, demonstration of neuroendocrine differentiation can help to ensure a correct diagnosis. Insulinoma-associated protein 1 (INSM1) is a novel neuroendocrine marker that has recently shown greater sensitivity than synaptophysin (SYN) and chromogranin (CHR) in the diagnosis of various neuroendocrine neoplasms. We compared the performance of these three markers across 10 examples of EMPSGC. All EMPSGCs expressed INSM1. Eight of ten were also immunoreactive for SYN; however, INSM1 staining was generally more intense and stained a greater proportion of the tumor cells. CHR staining was weak and focal in most cases. INSM1 staining was present in hidrocystoma-like components of cystic EMPSGC. These findings suggest that INSM1 may be more sensitive than SYN and CHR and thus valuable for establishing a diagnosis of EMPSGC.