Retinoid therapy is used for chemo-prevention in immuno-suppressed patients at high risk of developing skin cancer. The retinoid signalling molecule, tripartite motif protein 16 (TRIM16), is a regulator of keratinocyte differentiation and a tumour suppressor in retinoid-sensitive neuroblastoma. We sought to determine the role of TRIM16 in skin squamous cell carcinoma (SCC) pathogenesis. We have shown that TRIM16 expression was markedly reduced during the histological progression from normal skin to actinic keratosis and SCC. SCC cell lines exhibited lower cytoplasmic and nuclear TRIM16 expression compared with primary human keratinocyte (PHK) cells due to reduced TRIM16 protein stability. Overexpressed TRIM16 translocated to the nucleus, inducing growth arrest and cell differentiation. In SCC cells, TRIM16 bound to and down regulated nuclear E2F1, this is required for cell replication. Retinoid treatment increased nuclear TRIM16 expression in retinoid-sensitive PHK cells, but not in retinoid-resistant SCC cells. Overexpression of TRIM16 reduced SCC cell migration, which required the C-terminal RET finger protein (RFP)-like domain of TRIM16. The mesenchymal intermediate filament protein, vimentin, was directly bound and down-regulated by TRIM16 and was required for TRIM16-reduced cell migration. Taken together, our data suggest that loss of TRIM16 expression plays an important role in the development of cutaneous SCC and is a determinant of retinoid sensitivity.

SUMMARY A 64-year-old woman presented with diffuse and numerous pigmented macules on her face and upper back. Histopathological examination of a skin punch biopsy of the rash showed a lichenoid dermatitis. The most likely offending drug was pravastatin. Cessation of pravastatin resulted in gradual fading of the pigmentation. 3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors have previously been reported to cause lichenoid drug eruptions.

This study investigated the sensitivity and specificity of immunohistochemical (IHC) analysis using an anti-BRAF antibody to detect the presence of the BRAF V600E mutation in patients with metastatic melanoma. A total of 100 patients with American Joint Committee on Cancer stage IIIC unresectable or stage IV melanoma and who underwent tumor DNA BRAF mutation testing were selected. Paraffin-embedded, formalin-fixed melanoma biopsies were analyzed for the BRAF mutation status by independent, blinded observers using both conventional DNA molecular techniques and IHC with the novel BRAF V600E mutant-specific antibody, VE1. The antibody had a sensitivity of 97% (37/38) and a specificity of 98% (58/59) for detecting the presence of a BRAF V600E mutation. Of the BRAF-mutated cases, none of the non-V600E cases (including V600K) stained positive with the antibody (0/11). There were 5 cases with discordant BRAF mutation results. Additional molecular analysis confirmed the immunohistochemically obtained BRAF result in 3 cases, suggesting that the initial molecular testing results were incorrect. Two of these patients would not have received a BRAF inhibitor on the basis of the initial false-negative mutation testing result. Two cases remained discordant. The reported IHC method is an accurate, rapid, and cost-effective method for detecting V600E BRAF mutations in melanoma patients. Clinical use of the V600E BRAF antibody should be a valuable supplement to conventional mutation testing and allow V600E mutant metastatic melanoma patients to be triaged rapidly into appropriate treatment pathways.

In Reply.—We thank Douglas Craig Miller, MD, PhD, and authors Alireza Sepehr, MD, and Steven R. Tahan, MD, for their interest in our article reviewing the topic of borderline melanocytic tumors.1 In that article, we sought to provide logical and reasoned arguments, underpinned by biological and clinical evidence, supporting the hypothesis that there exists a small but significant subset of melanocytic tumors that have a limited capacity to metastasize to local lymph nodes but rarely spread to distant sites. We pointed out that this subgroup of tumors has a much more favorable prognosis than “conventional” melanomas and that the well-known, important prognosticators for conventional melanomas, such as tumor thickness and sentinel lymph node tumor-harboring status, do not appear to have the same significance for them.2–17 These facts support our proposal that such melanocytic tumors are biologically distinct and should be classified in a nosologic category separate from both melanomas and nevi.This concept is not new. In 1989, Smith and colleagues18 reported a series of tumors, which they interpreted as Spitz nevi, that involved regional lymph nodes but had not spread further to more-distant sites. Similarly, blue nevi metastasizing to lymph nodes have also been reported.19–21 Although some of these previously reported, metastasizing Spitz nevi and blue nevi have since been reinterpreted as melanomas,22,23 numerous large series with significant follow-up have highlighted the apparently favorable outcome of some “borderline” melanocytic tumors associated with regional lymph node metastases, such as atypical Spitzoid tumors and pigmented epithelioid melanocytomas.2,5,8–18,24 Despite this compelling evidence, Drs Sepehr and Tahan contend that even larger studies with longer follow-up are required before they will consider it appropriate to recognize additional, biologically distinct subgroups of melanocytic tumors. This begs the philosophic and rhetoric question, “How much evidence is required to challenge accepted dogma and present new hypotheses that better explain the data?”Whether or not the term melanocytoma, as we have proposed, is the best term for this distinct subset of tumors or another term, such as low-grade melanoma or perhaps borderline-malignant melanoma (akin to borderline ovarian carcinoma), is preferable is clearly controversial, as shown by the correspondence and remains a topic for further debate. Nevertheless, the evidence is already clear that the clinical behavior of these tumors justifies classifying them in a disease subgroup separate from both nevi and melanoma. Perhaps, in time, some tumors currently classified as atypical Spitzoid tumors and atypical deep penetrating nevuslike tumors will become known as Spitzoid melanocytomas and deep-penetrating melanocytomas, respectively. Furthermore, melanocytoma occurring in the central nervous system, which may recur or show invasive growth,25 could be termed central melanocytoma.Finally, in their correspondence, Drs Sepehr and Tahan mention the hypothetical case of an ulcerated, 5-mm-thick melanocytic tumor with 9 mitoses/mm2 occurring in an 80-year-old patient, which they classified as an atypical Spitzoid tumor. We respectfully disagree with the suggestion that any melanocytic tumor with these characteristics, particularly the high mitotic rate in a patient aged 80 years, should be classified as an atypical Spitzoid tumor. In our opinion, these features strongly suggest that the tumor is, in fact, a bona fide melanoma.

Ariyan and colleagues recently reported their experience with sentinel lymph node (SLN) biopsies from 263 patients with primary cutaneous melanoma. The SLNs were evaluated by intraoperative frozen section (F/S). Paraffin-embedded sections of the SLNs, stained with hematoxylin and eosin and immunohistochemically for S100 and HMB45, were assessed subsequently. Twentyeight patients (10.6%) had melanoma in a SLN, 23 (82%) of whom had tumor identified intraoperatively on F/S. The authors concluded that their series “attests to the reliability of frozen sections in identifying SLN harboring metastases.” Although we do not dispute that F/S examination of SLNs, when performed by a practiced and committed group such as that of Dr Aryian and his colleagues, can have an occasional role in some specialist melanoma treatment centers, we are concerned that use of this technique in other professional contexts can reduce the accuracy and reliability of the SLN biopsy procedure. Although the authors went to some length to suggest that their low yield of positive nodes (10.6%) compared with most large series (15% to 34%) reflected the high percentage of patients with thin primary tumors and fewer thick melanomas in their series, we cannot draw the same conclusion from the limited data presented. Indeed, the rate of positive SLNs for most groups of tumor thicknesses is lower than in the other series referenced in their article, and considerably lower than in a published (but uncited) report from the M D Anderson Cancer Center (Table 1). Unfortunately, the very limited clinicopathologic details provided prevent statistical comparison with other series. The inexplicably low rate of SLN positivity in the study raises the disturbing possibility that use of F/S might have led to a substantial number of false-negative SLNs resulting from loss of diagnostic tissue during the technical manipulations required for the F/S procedure, and/or that subsequent permanent section analysis may have been rendered more difficult by earlier freezing of some or all of the tissue. Our extensive combined experience with intraoperative F/S evaluation of SLNs, obtained during development of the modern SLN approach, was associated with a failure to identify melanoma micrometastases in 4% to 8% of ultimately positive patients. In view of this, and the practical considerations detailed below, we have long discontinued performing routine F/S examination on SLNs from melanoma patients. There is a major possibility that limited amounts of relatively localized diagnostic material in an SLN may be lost as a consequence of examining the node by F/S. First, substantial tissue is inevitably lost when “facing up” the frozen tissue block. Facing up is removal of tissue to obtain a section that contains all areas of the tissue. Melanoma micrometastases are most likely to lodge in the subcapsular region of an SLN and in adjacent and abutting lymphoid tissues around the central plane through the hilum and longest dimension of the node. It is absolutely critical that this portion of the SLN is included in the F/S and examined carefully. To obtain a full-face F/S that includes the subcapsular sinus region of the entire SLN, it is unavoidable that substantial nodal tissue is lost during facing up. Because it is difficult to make the cut surface of the SLN sit flat during freezing of the tissue, some discarded tissue inevitably derives from the critical subcapsular region. When a fresh SLN is bisected, the nodal capsule retracts and central tissue bulges from the cut surface. Metastases that are localized only in the central part of the node, as is occasionally observed, may also be discarded as a result of the facing-up procedure. Second, because tissue and cellular preservation is generally inferior in frozen

The pathologist often has a difficult task in evaluating melanocytic lesions. For lesions involving the face the consequences of misdiagnosis are compounded for both cosmetic and therapeutic reasons. In this article, the pathological features of common and uncommon benign and malignant melanocytic lesions are reviewed and pitfalls in their diagnosis are highlighted. Benign lesions resembling melanomas include regenerating naevus, "irritated" naevus, combined naevus, "ancient naevus", Spitz naevus, dysplastic naevus, halo naevus, variants of blue naevi, balloon and clear cell naevi, neurotised naevus and desmoplastic naevus. Melanomas that can easily be missed on presentation include desmoplastic, naevoid, regressed, myxoid and metastatic types as well as so-called malignant blue naevi. Pathological clues to benign lesions include good symmetry, V-shaped silhouette, absent epidermal invasion, uniform cellularity, deep maturation, absent or rare dermal mitoses and clustered Kamino bodies. Features more commonly present in melanomas include asymmetry, peripheral epidermal invasion, heavy or "dusty" pigmentation, deep and abnormal dermal mitoses, HMB45 positivity in deep dermal melanocytes, vascular invasion, neurotropism and satellites. Familiarity with the spectrum of melanocytic lesions and knowledge of the important distinguishing features should assist in interpretation. Occasionally, the use of ancillary studies may also provide additional useful information. Application of standard criteria for diagnosing such lesions should enable the correct diagnosis to be established in most cases.

The addition of MEKi to BRAFi did not result in significant reduction in immune infiltration in EDT biopsies. This provides support for conducting trials that combine MAPKi with immune checkpoint inhibitors in the hope of improving complete and durable response rates. PD-L1 expression at PROG on MAPK inhibitors varied according to baseline expression suggesting that combining MAPKi with immunotherapies concurrently may be more effective in patients with PD-L1 expression and TILs in baseline melanoma samples.

If melanoma is suspected, initial excision biopsy is recommended. Wide excision margins are then based on reported tumour thickness. Sentinel lymph node biopsy provides important prognostic information and a probable survival benefit for patients with intermediate thickness melanomas. Other staging tests are not indicated in patients with clinically localised primary melanomas. Complete lymph node dissection is required if microscopic or macroscopic disease is present in regional nodes. Intransit metastases are best managed at specialist melanoma treatment centres. For patients with widespread systemic metastases, new drug treatments including BRAF inhibitors and anti-CTLA4 antibodies are prolonging survival, but unfortunately most patients ultimately relapse.

Patients with no history of melanoma occasionally present with apparently metastatic melanoma in the lungs, but have no evidence of a primary melanoma. The aims of this study were to investigate the role of surgical resection in the treatment of such patients, and to examine the evidence for a diagnosis of primary pulmonary melanoma in each case. Patients with an unknown primary melanoma who presented with pulmonary disease and subsequently underwent surgical resection were identified from the Sydney Melanoma Unit database. Fifteen patients fulfilled the study criteria. Multiple lesions were present in four. Eight wedge resections and 10 lobectomies were performed. The patients' median survival was 32 months and the 5-year actuarial survival was 42%. This compares with the overall Sydney Melanoma Unit experience of lung resection for melanoma in 83 patients, where the median survival was 19 months and the 5-year survival was 22%. Resection of pulmonary disease in melanoma patients with an unknown primary lesion can result in long-term survival, and even apparent cure. It is possible that some of the patients in this series had primary melanoma of the lung, but this is impossible to prove.