Evolving concepts in melanoma classification and their relevance to multidisciplinary melanoma patient care

In the initial period after melanoma was recognised as a disease entity in the early 1800's, it was subclassified on the basis of its presumed origin (from a precursor naevus, from a melanocytic precursor lesion acquired during adult life or in previously blemish-fee skin). In 1967 the eminent American pathologist, Dr Wallace Clark, proposed a histogenetic classification for melanoma in which the disease was subdivided predominantly on the basis of histopathological features of the intra-epidermal component of the tumour adjacent to any dermal invasive component. The subtypes were superficial spreading melanoma (SSM), lentigo maligna melanoma (LMM) and nodular melanoma (NM). Whilst additional entities, including acral lentiginous melanoma, mucosal melanoma, desmoplastic melanoma and naevoid melanoma have since been recognised, SSM, LMM and NM remain in the latest (2006) version of the WHO melanoma classification. Clark's histogenetic classification has been criticised because the criteria upon which it is based include clinical features (such as the site of the melanoma) and non-tumourous histopathological features (such as the character of the associated epidermis and the degree of solar elastosis) and also because of overlap in defining features, lack of an independent association with patient outcome and minimal relevance as a determinant of clinical management. However, such criticisms fail to acknowledge its importance in highlighting the myriad of clinical and histological guises of melanoma, which if not recognized by clinicians and pathologists will inevitably lead to a delay in diagnosis and a concomitant adverse clinical outcome. Recently, mutually exclusive oncogenic mutations in melanomas involving NRAS (15-20%), BRAF (50%), CKIT (2%), and GNAQ/GNA11 (50% of uveal melanomas) have been identified. This might herald the beginning of a new molecular classification of melanoma in which the biologically distinct subsets share a common oncogenic mechanism, behave clinically in a similar fashion and require similar clinical management. These discoveries are already being successfully exploited as therapeutic targets in clinical trials of metastatic melanoma patients with promising activity. Whilst there remains much to be discovered in this rapidly evolving field, there is already great optimism that more rational and effective therapies for melanoma patients will soon be widely available.     

BRAF在前列腺癌组织中表达及意义

Objective  

The aim of this study was to investigate the expression of BRAF of prostate cancer, and to explore its relations with clinic-pathological factors.     

Less‐invasive diagnosis of disseminated epithelioid glioblastoma harboring BRAF V600E mutation by cerebrospinal fluid analysis—A case report

Spinal dissemination in epithelioid glioblastoma can be diagnosed by cerebrospinal fluid cytology and liquid biopsy to detect BRAF V600E mutation.     

Ki67 expression levels are a better marker of reduced melanoma growth following MEK inhibitor treatment than phospho-ERK levels

The loss of tumour phospho-extracellular responsive kinase (pERK) positivity is the major treatment biomarker for mitogen-activated protein kinase/extracellular responsive kinase (MEK) inhibitors. Here, we demonstrate that there is a poor correlation between pERK inhibition and the anti-proliferative effects of MEK inhibitors in melanoma cells. We suggest that Ki67 is a better biomarker for future clinical studies.     

Detection of mutated BRAFV600E variant in circulating DNA of stage III-IV melanoma patients

BRAFV600E is the most represented somatic point mutation in cutaneous melanoma, thus providing a unique molecular marker for this disease. The development of efficient methods for its detection in free circulating DNA of patients may lead to the improvement of diagnostic and prognostic tools. With this aim, we evaluated whether BRAFV600E represents a detectable marker in the plasma/serum from melanoma patients in a pilot study. Circulating cell-free DNA was extracted from the serum or plasma of 15 healthy donors and 41 melanoma patients at different clinical stages and obtained either presurgery or after surgery during follow-up. Quantitative analysis showed higher levels of circulating free DNA in patients compared to controls, with the highest levels detected in samples obtained presurgery and at stage IV. Four different PCR methods were compared for their capacity to amplify a few copies of BRAFV600E in wild-type DNA. BRAFV600E was detectable in circulating DNA of 12 patients and in none of the controls; only 1 PCR method reproducibly amplified BRAFV600E. Positive samples were obtained from 8/13 patients at stage IV and from 4/24 patients at stage III, but not in 4 patients at stage I-II; half of the positives were obtained presurgery and half at follow-up. Correspondence between circulating DNA and related tumors were examined for 20 patients, and a correlation was found for stage IV patients. In conclusion, this method can be utilized for monitoring the disease in stage IV melanoma patients but it appears unsatisfactory for the early detection of melanoma.     

Extracellular signal‐regulated kinase activation of self‐healing Langerhans cell histiocytosis: A case report

A 3‐month‐old boy developed small papules on his trunk. After the papules increased in number, the patient was diagnosed with Langerhans cell histiocytosis based on the pathological findings. He was referred to our department for further examination. Upon initial examination, the papules and nodules were scattered on his back, abdomen and lumbar region. Because he did not present with any organ involvement except the skin, he was diagnosed with single‐system and skin‐limited Langerhans cell histiocytosis. Skin rashes were treated with a topical steroid and started regressing 3 months after onset. All papules disappeared 6 months after onset. In this boy, the Langerhans cell histiocytosis tumor cells expressed phosphorylated extracellular signal‐regulated kinases. In Langerhans cell histiocytosis, BRAF V600E and other genes are known to mutate to act as driver mutations in stem cells of the myeloid dendritic cell lineage. Consequently, extracellular signal‐regulated kinases are continuously activated, which contributes to Langerhans cell histiocytosis carcinogenesis.     

Malignant melanoma with metaplastic cartilaginous transdifferentiation: A case report

Malignant melanoma is notorious for its remarkable morphological variation and aberrant histopathological patterns. However, melanoma with prominent cartilaginous transdifferentiation simulating chondrosarcoma is extremely rare. A 75‐year‐old male developed a swelling in his left inguinal region and was diagnosed with a metastatic melanoma, which was found to harbor a BRAF V600E mutation. Later on, the left inguinal lymph node was excised and immunohistochemistry done on the specimen revealed an undifferentiated component negative for S‐100 protein, HMB‐45 and Melan‐A and a cartilaginous component positive for S‐100 protein and diffusely positive for BRAF V600E mutation. To our knowledge, there are around 14 cases reported in the literature of malignant melanoma with pure cartilaginous transdifferentiation. In all cases, immunohistochemistry of the cartilaginous component was positive for S‐100, which is not an indicator of melanoma because cartilage expresses S‐100. BRAF mutational studies support that the tumor arose from a common melanoma cell that harbored the mutation and subsequently transdifferentiated. This case illustrates the importance of an accurate and thorough clinical assessment when it comes to the diagnosis of melanomas as they are notable for their impressive degree of morphologic variability. Moreover, this report helps shed light on the use of immunohistochemical analysis to reach a definitive diagnosis.     

Clinicopathologic features and immunohistochemical spectrum of 11 cases of epithelioid malignant peripheral nerve sheath tumors,including INI1/SMARCB1 results and BRAF V600E analysis

Epithelioid malignant peripheral nerve sheath tumor (MPNST) is a rare, relatively less chemosensitive sarcoma. We report clinicopathologic features of 11 epithelioid MPNSTs, including rare forms, along with INI1 immunostaining and BRAF V600E mutation results. BRAF V600E mutation was tested by Real‐time polymerase chain reaction (PCR) technique. Eleven tumors occurred in six men and five women (M:F ratio = 0.85:1) within an age range of 5–73 years (average = 44), mostly in lower limbs (five), followed by upper limbs (four). Tumor size (n = 6), varied from 3.1 to 15 cm (average = 8.3). Histopathologically, most tumors were multilobular, characterized by epithelioid to round‐shaped, malignant cells, along with spindle cells (three cases), “rhabdoid‐like” cells (seven cases) and pleomorphic giant cells (single case). By immunohistochemistry, tumor cells were positive for S100 protein (11/11) (100%), EMA (3/7) (42.8%), pan CK(2/7) (28.5%), and HMB45 (1/11) (9%), while these were negative for Melan A (0/11) and INI1 (3/11), including a single tumor, displaying HMB45 positivity. BRAF V600E mutation was positive in 1/8 cases, that lacked melanocytic marker expression. All patients (n = 5) were treated by surgical resection. During follow‐up (n = 8, median duration = 23 months), four patients developed tumor recurrences and four developed metastasis, mostly to lymph nodes (3). Finally, four patients were alive with disease, two were alive with no evidence of disease, and two patients died of disease. Epithelioid MPNSTs have a diverse histopathologic spectrum. Loss of INI1 is useful, including in identifying rare forms of epithelioid MPNST, displaying melanocytic differentiation. Most tumors are treated by surgical resection. Loss of INI1 and the presence of BRAF V600E mutation in some cases raises future possibility of exploring targeted therapy in those, rare epithelioid MPNSTs.