Marion Wobser

Primary cutaneous marginal zone lymphomas with plasmacytic differentiation show frequent IgG4 expression.

The expression of IgG4 in malignant B-cell lymphomas has only partially been studied. Recent reports described single cases of marginal zone lymphomas arising in the ocular adnexae that express IgG4. Moreover, a subset of dura-associated marginal zone lymphomas appear to express IgG4 as well. We investigated IgG4 expression in a more systematic manner in a large cohort of marginal zone lymphoma specimens derived from the archive of our institute. Overall, we examined 169 marginal zone lymphomas of various primary sites that displayed a distinct plasmacytic differentiation and light chain restriction, allowing for a detailed investigation of the immunoglobulin heavy chain expression in these tumors by immunohistochemistry. Unexpectedly, primary cutaneous marginal zone lymphomas showed frequent IgG4 expression. Although only 1 out of 120 noncutaneous marginal zone lymphomas, located in the ocular adnexae, expressed IgG4, 19 of 49 (39%) primary cutaneous marginal zone lymphomas showed this feature, constituting the highest expression rate of IgG4 reported to date in any B-cell lymphoma. None of the IgG4-positive cutaneous marginal zone lymphomas with available clinical data showed evidence of a preexisting systemic IgG4-related disease, suggesting a localized immunologic IgG4-driven pathogenetic process at early stages of the disease. IgG4-positive and IgG4-negative primary cutaneous marginal zone lymphomas did not significantly differ in architectural features of the infiltrate or the composition of the reactive T-cell infiltrate as determined by analysis of T-cell content, CD4/CD8 ratio, and content of FOXP3- and PD1-positive T cells. Although the pathogenetic role of IgG4 expression in a significant subset of primary cutaneous marginal zone lymphomas with plasmacytic differentiation remains unclear at present, the demonstration of IgG4 expression in a marginal zone lymphoma involving the skin might be a helpful clue in the routine diagnostic setting, as these tumors will almost invariably be of primary cutaneous origin with an extremely low risk of spread to noncutaneous sites and an excellent prognosis.

Mosaic Activating Mutations in GNA11 and GNAQ Are Associated with Phakomatosis Pigmentovascularis and Extensive Dermal Melanocytosis

Common birthmarks can be an indicator of underlying genetic disease but are often overlooked. Mongolian blue spots (dermal melanocytosis) are usually localized and transient, but they can be extensive, permanent, and associated with extracutaneous abnormalities. Co-occurrence with vascular birthmarks defines a subtype of phakomatosis pigmentovascularis, a group of syndromes associated with neurovascular, ophthalmological, overgrowth, and malignant complications. Here, we discover that extensive dermal melanocytosis and phakomatosis pigmentovascularis are associated with activating mutations in GNA11 and GNAQ, genes that encode Gα subunits of heterotrimeric G proteins. The mutations were detected at very low levels in affected tissues but were undetectable in the blood, indicating that these conditions are postzygotic mosaic disorders. In vitro expression of mutant GNA11R183C and GNA11Q209L in human cell lines demonstrated activation of the downstream p38 MAPK signaling pathway and the p38, JNK, and ERK pathways, respectively. Transgenic mosaic zebrafish models expressing mutant GNA11R183C under promoter mitfa developed extensive dermal melanocytosis recapitulating the human phenotype. Phakomatosis pigmentovascularis and extensive dermal melanocytosis are therefore diagnoses in the group of mosaic heterotrimeric G-protein disorders, joining McCune-Albright and Sturge-Weber syndromes. These findings will allow accurate clinical and molecular diagnosis of this subset of common birthmarks, thereby identifying infants at risk for serious complications, and provide novel therapeutic opportunities.

Primary hypertrophic osteoarthropathy with digital clubbing and palmoplantar hyperhidrosis caused by 15-PGHD/HPGD loss-of-function mutations

Abstract:  Digital clubbing is the most prominent feature in primary (PHO) and secondary (pulmonary) hypertrophic osteoarthropathy (HO). Homozygous and compound heterozygous germline mutations in the 15‐hydroxyprostaglandin dehydrogenase (HPGD) gene encoding the major prostaglandin PGE2 catabolizing enzyme have been recently described in familial PHO cases. Elevated prostaglandin levels in affected individuals with cytokine‐mediated tissue remodelling and vascular stimulation may underlie PHO and associated features as hyperhidrosis, acroosteolysis, pachyderma, periostosis and arthritis. We present clinical and biochemical data of three unrelated PHO families with HPGD mutations. The truncating mutation c.175_176del was found in two of our families and in one of the recently described pedigrees, all of European origin. We present evidence that c.175_176del is a recurrent mutation rather than an ancient founder allele. Two novel heterozygous HPGD mutations, the nonsense mutation c.118G>T (p.Glu40X) and the missense mutation c.563C>T (p.Thr188Ile), could be identified in a third family. We postulate that all HPGD mutations constitute loss‐of‐function alleles due to protein truncation or missense changes that affect hydrogen bonds lining the 15‐PGDH enzyme reaction cavity. Elevated prostaglandin levels may give rise to use of non‐steroidal anti‐inflammatory drugs; however, therapeutic strategies have not been reported to date. Naproxen treatment in one of our mutation‐positive patients resulted in alleviation of pain caused by periostosis and arthritis as well as reduction in substantially elevated prostaglandin levels, while no significant effects on digital clubbing, hyperhidrosis and pachyderma were observed. Further experience with nonsteroidal anti‐inflammatory drugs in PHO is awaited.

Therapy of metastasized Merkel cell carcinoma with liposomal doxorubicin in combination with radiotherapy

Background: Merkel cell carcinoma is a rare skin cancer of neuroendocrine origin, which is characterized by a high rate of recurrence, metastatic spread and mortality. Because of its rarity, evidence‐based therapeutic regimens are difficult to establish. Merkel cell carcinoma is known to be both radio‐ and chemosensitive. Toxicity is a key factor in assessing any regimen, as the patients are usually elderly and likely to have other significant medical problems.

Bcl-2 expression in rituximab refractory cutaneous B-cell lymphoma.

Rituximab has been established as an effective and safe therapy for cutaneous B-cell lymphoma (CBCL). Different survival pathways, that is the Raf/MEK/Erk- or the p38MAPK cascade, have been suggested as downstream mediators of rituximab and may be involved in treatment failure. Biopsies from four patients, suffering from different subtypes of CBCL, which were obtained at various time points of relapse during or after therapy with 375 mg rituximab per m2 of body surface area, were analysed for the expression of CD20, CD3, Ki-67, Raf-kinase inhibitory protein (RKIP) and bcl-2 by immunohistochemistry. No CD20-loss variants, that is the suggested main tumour escape mechanism to rituximab therapy, were observed in any specimen of relapsing CBCL. Notably, the expression of proapoptotic RKIP remained increased in these tumour samples. This was concomitated by a constant to slightly reduced proliferation status as demonstrated by Ki-67 staining. However, relapsing CBCL exhibited a strong upregulation of the antiapoptotic molecule bcl-2 in comparison to pretherapeutic levels. The immunohistochemical analyses of this case series of rituximab refractory CBCL suggest that upregulation of bcl-2 may play a major role in therapy resistance.

Primary cutaneous diffuse large B-cell lymphoma, leg-type, treated with a modified R-CHOP immunochemotherapy – diagnostic and therapeutic challenges

Background: Primary cutaneous diffuse large B‐cell lymphoma (PCLBCL) represents a rare subtype among primary cutaneous B‐cell lymphoma exhibiting a characteristic genetic background, an aggressive clinical course and a high relapse rate under different therapeutic regimen. Therefore, PCLBCL has a rather restricted prognosis.

Expression pattern of the lymphatic and vascular markers VEGFR-3 and CD31 does not predict regional lymph node metastasis in cutaneous melanoma

Malignant melanoma of the skin preferentially metastasises via the lymphatic system. Novel molecular biomarkers, which are involved in malignant transformation, proliferation, angiogenesis and lymphangiogenesis, are currently under investigation to elucidate the risk for lymph node metastasis. To this end, the vascular endothelial growth factors VEGF-C and VEGF-D have been identified to promote lymphangiogenesis and lymphatic spread through activation of its receptor, Vascular endothelial growth factor receptor-3 (VEGFR-3). Prompted by this assumption, we estimated the degree of lymphangiogenesis by semiquantitative immunohistochemical analysis of the expression of VEGFR-3 and the panvascular marker CD31 in primary cutaneous melanoma (n=26) and correlated these findings with the sentinel lymph node (SLN) status. The cohort was selected for matched prognostic markers in SLN-positive and SLN-negative patients. In contrast to other studies, we observed an inverse correlation between expression of these markers with lymph node metastases. Additionally, no difference between intratumoral versus peritumoral CD31- or VEGFR-3 expression on blood vessels versus lymphatic capillaries could be detected. Interestingly, VEGFR-3 upregulation was not restrained to vascular structures but also appeared on tumor cells. In summary, in our series VEGFR-3/CD31 immunohistochemical staining of primary melanoma does not serve as a valid marker to predict lymph node involvement. As lymphatic spread is a complex, multi-step process, several different biomarkers have to be combined to define new prognostic subgroups in cutaneous melanoma.

RB1 is the crucial target of the Merkel cell polyomavirus Large T antigen in Merkel cell carcinoma cells.

The pocket protein (PP) family consists of the three members RB1, p107 and p130 all possessing tumor suppressive properties. Indeed, the PPs jointly control the G1/S transition mainly by inhibiting E2F transcription factors. Notably, several viral oncoproteins are capable of binding and inhibiting PPs. Merkel cell polyomavirus (MCPyV) is considered as etiological factor for Merkel cell carcinoma (MCC) with expression of the viral Large T antigen (LT) harboring an intact PP binding domain being required for proliferation of most MCC cells. Therefore, we analyzed the interaction of MCPyV-LT with the PPs. Co-IP experiments indicate that MCPyV-LT binds potently only to RB1. Moreover, MCPyV-LT knockdown-induced growth arrest in MCC cells can be rescued by knockdown of RB1, but not by p107 or p130 knockdown. Accordingly, cell cycle arrest and E2F target gene repression mediated by the single PPs can only in the case of RB1 be significantly reverted by MCPyV-LT expression. Moreover, data from an MCC patient indicate that loss of RB1 rendered the MCPyV-positive MCC cells LT independent. Thus, our results suggest that RB1 is the dominant tumor suppressor PP in MCC, and that inactivation of RB1 by MCPyV-LT is largely sufficient for its growth supporting function in established MCPyV-positive MCC cells.

CD68 expression is a discriminative feature of indolent cutaneous CD8‐positive lymphoid proliferation and distinguishes this lymphoma subtype from other CD8‐positive cutaneous lymphomas

Indolent cutaneous CD8+ lymphoid proliferation is a recently described rare entity among cutaneous T‐cell lymphomas that typically presents with solitary skin lesions at acral sites. Separation from otherwise aggressive T‐cell lymphomas bearing a cytotoxic CD8+ phenotype is fundamental to avoid unnecessary harmful treatment. However, up to now, no reliable discriminative marker has been identified.

Pitfall scarring alopecia: Favus closely mimicking lichen planus

We describe a woman presenting primarily with slowly progressing scarring alopecia. Course, symptoms, and clinical picture were highly suggestive for lichen planus. But mycological investigations revealed that cicatricial alopecia was caused by a specific infection with Trichophyton schoenleinii running a chronic course with minimal skin inflammation.