Spindle cell tumor with CD34 and S100 co-expression and distinctive stromal and perivascular hyalinization showing EML4-ALK fusion.

Recently, a novel group of CD34+ and S100+ spindle cell tumors with distinctive stromal and perivascular hyalinization showing recurrent gene fusions involving RAF1, BRAF, NTRK1/2/3, and RET has been identified. ALK rearrangements have been rarely reported in this group of tumors. We report a 24-year-old woman with a 1.5-cm pink mass of the scalp. The tumor was made of spindle cells organized in fascicles or haphazardly arranged in a patternless architecture, with areas of stromal and perivascular hyalinization. The tumor cells diffusely expressed CD34 and S100, without SOX-10 expression. The tumor showed diffuse immunopositivity for ALK. RNA sequencing using next-generation sequencing (NGS) detected an EML4-ALK fusion. This case extends the spectrum of this newly described group of CD34+/S100+ spindle cell tumors at the molecular-genetic level. Dermatopathologists should be aware of this recent entity, as it may fall in the differential diagnosis of many other spindle cell tumors with CD34 expression. NGS-based techniques should be performed when facing spindle cell tumors with similar morphology and immunophenotype. Identification of kinase fusions is essential for the precise classification and better knowledge of these tumors, and for targeted therapy in rare aggressive cases.

Severe skin toxicity with organ damage under the combination of targeted therapy following immunotherapy in metastatic melanoma.

Targeted therapy combination (TTC: antiRAF+antiMEK) is known to improve metastatic melanoma survival. Few severe skin toxicities (grade ≥3) are described with first-line TTC (17% for vemurafenib+cobimetinib and none for dabrafenib+trametinib) in a phase III trial. Among our 42 patients treated by TTC between January 2014 and March 2017, 4.8% (2/42) of those treated in the first line presented severe skin rash versus 19% (8/42) of patients treated in the second line after previous immunotherapy. In particular, we observed one case of Stevens-Johnson syndrome and four cases of severe drug reaction with eosinophilia and systemic symptoms syndrome under TTC in patients who had received immunotherapy previously. Thus, previous immunotherapy appears to play an important role in the skin rash onset and severity induced by TTC.

BRAF inhibitor discontinuation and rechallenge in advanced melanoma patients with a complete initial treatment response.

BRAF inhibitors (BRAFi), a targeted therapy, are used to treat metastatic late-stage melanomas harbouring the BRAF-V600 mutation (found in about 50% of melanomas). The targeted therapy is generally maintained until tumour progression or major toxicity occurs, although responses are often limited in time. It is unknown whether melanoma patients achieving a complete response with targeted therapy can safely discontinue treatment. We retrospectively observed the clinical course of patients with metastatic melanoma who discontinued BRAFi therapy after achieving a complete response and those with an incomplete response combined with surgical removal of the remaining tumours. We also evaluated the effectiveness of BRAFi in these patients after recurrence. In 11 patients, the best response was diagnosed after a median BRAFi treatment duration of 105 (29-341) days. The median follow-up after BRAFi initiation was 769 (435-1765) days. Recurrence was observed in all 11 patients (100%), median: 82 (27-322) days. Five patients achieved a complete response, with a median progression-free survival after cessation of 136.5 (34-322) days versus 82 (27-144) days for six patients with an incomplete response combined with surgical removal of remaining tumours. Baseline characteristics and time to best response and to discontinuation did not influence the rate of relapse. Subsequently, eight patients were rechallenged with a BRAFi. The median progression-free survival time after BRAFi rechallenge was 222.5 (15-425) days. The three remaining patients received treatments other than BRAFi. Our findings may be valuable with respect to ongoing clinical trials of combinations of targeted therapies and immunomodulatory antibodies.