A characteristic feature of classic PXE, an autosomal recessive disorder caused by mutations in the ABCC6 gene, is aberrant mineralization of connective tissues, particularly the elastic fibers. Here, we report a family with PXE-like cutaneous features in association with multiple coagulation factor deficiency, an autosomal recessive disorder associated with GGCX mutations. The proband and her sister, both with severe skin findings with extensive mineralization, were compound heterozygotes for missense mutations in the GGCX gene, which were shown to result in reduced γ-glutamyl carboxylase activity and in under-carboxylation of matrix gla protein. The proband’s mother and aunt, also manifesting with PXE-like skin changes, were heterozygous carriers of a missense mutation (p.V255M) in GGCX and a null mutation (p.R1141X) in the ABCC6 gene, suggesting digenic nature of their skin findings. Thus, reduced γ-glutamyl carboxylase activity in individuals either compound heterozygous for a missense mutation in GGCX or with haploinsufficiency in GGCX in combination with heterozygosity for ABCC6 gene expression results in aberrant mineralization of skin leading to PXE-like phenotype. These findings expand the molecular basis of PXE-like phenotypes, and suggest a role for multiple genetic factors in pathologic tissue mineralization in general.

Summary Introduction:  Myeloid sarcomas are extramedullary lesions composed of myeloid lineage blasts that typically form tumorous masses and may precede, follow, or occur in the absence of systemic acute myeloid leukemia. They most commonly involve the skin and soft tissues, lymph nodes, and gastrointestinal tract and are particularly challenging to diagnose in patients without an antecedent history of acute myeloid leukemia. Methods:  We conducted a search of the English language medical literature for recent studies of interest to individuals involved in the diagnosis of myeloid sarcoma. Results:  The differential diagnosis includes non‐Hodgkin lymphoma, blastic plasmacytoid dendritic cell neoplasm, histiocytic sarcoma, melanoma, carcinoma, and (in children) small round blue cell tumors. The sensitivity and specificity of immunohistochemical markers must be considered when evaluating a suspected case of myeloid sarcoma. A high percentage of tested cases have cytogenetic abnormalities. Conclusion:  A minimal panel of immunohistochemical markers should include anti‐CD43 or anti‐lysozyme as a lack of immunoreactivity for either of these sensitive markers would be inconsistent with a diagnosis of myeloid sarcoma. Use of more specific markers of myeloid disease, such as CD33, myeloperoxidase, CD34 and CD117 is necessary to establish the diagnosis. Other antibodies may be added depending on the differential diagnosis. Identification of acute myeloid leukemia‐associated genetic lesions may be helpful in arriving at the correct diagnosis.

Purely cutaneous disease without the characteristic lymphadenopathy is rare but has been increasingly reported in the literature. Compared with patients with systemic Rosai-Dorfman disease, patients with primary cutaneous Rosai-Dorfman disease are older, women are more commonly affected, and whites are more likely than blacks to be afflicted.

Background Gene expression profiling (GEP) has been integrated into cancer treatment decision‐making in multiple neoplasms. We prospectively evaluated the prognostic utility of the 31‐GEP test (DecisionDx‐Melanoma, Castle Biosciences, Inc) in cutaneous melanoma (CM) patients undergoing sentinel node biopsy (SNB). Methods One hundred fifty‐nine patients (age 26‐88) diagnosed with melanoma between 01/2013 and 8/2015 underwent SNB and concurrent GEP testing. GEP results were reported as low‐risk Class 1 (subclasses 1A and 1B) or high‐risk Class 2 (subclasses 2A and 2B). Statistical analyses were performed with chi‐square analysis, t tests, log‐rank tests, and Cox proportional hazard models. Recurrence‐free survival (RFS) and distant metastasis‐free survival (DMFS) were estimated using Kaplan‐Meier method. Results Median follow‐up was 44.9 months for event‐free cases. Median Breslow thickness was 1.4 mm (0.2‐15.0 mm). There were 117 Class 1 and 42 Class 2 patients. Gender, age, Breslow thickness, ulceration, SNB positivity, and AJCC stage were significantly associated with GEP classification ( P < 0.05 for all). Recurrence and distant metastasis rates were 5% and 1% for Class 1 patients compared with 55% and 36% for Class 2 patients. Sensitivities of Class 2 and SNB for recurrence were 79% and 34%, respectively. Of 10 SNB‐positive/Class 2 patients, 9 recurred. By multivariate analysis, only SNB result and GEP class were statistically associated with both RFS ( P = 0.008 and 0.0001) and DMFS ( P = 0.019 and 0.001). Conclusions Gene expression profiling Class 2 result and SNB positivity were independently associated with recurrence and distant metastasis in primary CM patients. GEP testing may have additive prognostic utility in initial staging work‐up of these patients.

Mucoepidermoid carcinoma (MEC) of the skin is an exceedingly rare but distinctive neoplasm with respect to its histopathologic features. It is similar if not identical in most respects to MEC of the salivary gland, a neoplasm whose prognosis is correlated with the pathologic grade. We report a case of MEC of the skin in a 79-year-old white woman who presented with an axillary mass. Beneath an unremarkable epidermis, a circumscribed, cystic neoplasm, unattached to the surface, was characterized by the presence of vague lobules of low-grade-appearing squamous cells accompanied by mucigenic and clear cells. A mucin stain highlighted the mucigenic cells and immunohistochemistry revealed pan-cytokeratin, cytokeratin 7, polyclonal carcinoembryonic antigen, and epithelial membrane antigen positivity. The cytokeratin 20 and gross cystic disease fluid protein were nonreactive. Inconsistency was encountered in the literature where some confusion existed as to whether MEC is synonymous with adenosquamous carcinoma of the skin. Elsewhere in the body, the latter tumor type is a squamous and gland-forming neoplasm with intermediate- to high-grade features rather than a tumor with mucigenic cells intermingled among intermediate and squamous cells. As in the case of MEC and adenosquamous carcinoma elsewhere in extracutaneous sites, we would propose that a pathologic distinction should be made in the skin for the sake of consistency and for prognostic purposes. Additionally, the immunophenotype of our case is similar to at least two other cases of cutaneous MEC, as well as MEC of the salivary gland, to support the hypothesis that this neoplasm is adnexal rather than epidermal in origin.

PEComas represent a family of uncommon mesenchymal tumors composed of "perivascular epithelioid cells" with a distinct immunophenotype that typically shows both myogenic and melanocytic differentiation. The PEComa family includes angiomyolipoma (AML), clear cell They also often express strong diffuse CD10, leading to potential confusion with metastatic renal cell carcinoma. Most cases behave indolently. We report 5 additional cases of this rare entity. All showed classic histologic features and expression of either HMB-45 and/or Melan-A/MART-1. Four cases were tested for myogenic markers (2 were positive & 2 were negative).

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We conducted a retrospective study of patients with cutaneous myeloid sarcoma, from 2 tertiary care institutions. Eighty-three patients presented, with a mean age of 52 years. Diagnosis of myeloid sarcoma in the skin was difficult due to the low frequency of myeloperoxidase and/or CD34+ cases (56% and 19% of tested cases, respectively). Seventy-one of the 83 patients (86%) had ≥ 1 bone marrow biopsy. Twenty-eight (39%) had acute myeloid leukemia with monocytic differentiation. Twenty-three had other de novo acute myeloid leukemia subtypes. Thirteen patients had other myeloid neoplasms, of which 4 ultimately progressed to an acute myeloid leukemia. Seven had no bone marrow malignancy. Ninety-eight percent of the patients received chemotherapy, and approximately 89% died of causes related to their disease. Cutaneous myeloid sarcoma in most cases represents an aggressive manifestation of acute myeloid leukemia. Diagnosis can be challenging due to lack of myeloblast-associated antigen expression in many cases, and difficulty in distinguishing monocyte-lineage blasts from neoplastic and non-neoplastic mature monocytes.