Extensive tumoral melanosis associated with ipilimumab-treated melanoma

Immune checkpoint inhibitor-induced cutaneous toxicities: a review of histopathologic and clinical features

Immune checkpoint inhibitors (ICIs) represent an emerging treatment option for a variety of cancer types. Through inhibition of programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1), and/or cytotoxic lymphocyte-associated antigen-4 (CTLA-4), ICIs activate the host's immune system causing a heightened anti-tumor response. However, off-target effects of ICIs can result in numerous different immune-related cutaneous adverse events (irCAEs). Beyond impacting quality of life, irCAEs can lead to dose limitations or discontinuation of anti-cancer therapies. Correct diagnosis is necessary for expedient and appropriate management. Skin biopsies are often performed to increase diagnostic accuracy and guide clinical management. An extensive literature review was performed using the PubMed database to identify the reported clinical and histopathologic features of irCAEs. This comprehensive review primarily details the histopathologic features of various irCAEs reported to date. Clinical presentation and immunopathogenesis are also discussed in relation to histopathology.

Tumoral melanosis mimicking residual melanoma in the setting of talimogene laherparepvec treatment

Talimogene laherparepvec (T-VEC) has become an increasingly popular treatment option for surgically non-resectable, recurrent melanoma, usually of cutaneous metastases. The complete response (CR) rate has been reported to be ~20% with a median of ~9 months to achieve it. In real-world practice, decrease of tumor size often occurs rapidly within the first 2–3 months, while improvement of the pigmentation takes several more months. Such clinical observation of lasting pigmentation could be explained by tumorous melanosis—a histopathological term referring to the presence of a melanophage-rich inflammatory infiltrate without remaining viable tumor cells. Herein, we report six patients with metastatic cutaneous melanoma who were treated with T-VEC. Biopsies were performed after observing clinical responses in the injected tumors. Pathological evaluation demonstrated non-viable or absent tumor tissue with tumorous melanosis in all cases. To accurately assess response to therapy and potentially decrease unnecessary additional T-VEC treatments, serial biopsy of ‘stable’ lesions should be considered to assess the presence or absence of viable tumor.

Cutaneous Events Associated with Immunotherapy of Melanoma: A Review

Immunotherapy with checkpoint inhibitors significantly improves the outcome for stage III and IV melanoma. Cutaneous adverse events during treatment are often reported. We herein aim to review the principal pigmentation changes induced by immune check-point inhibitors: the appearance of vitiligo, the Sutton phenomenon, melanosis and hair and nail toxicities.

Cutaneous Toxicities in the Setting of Immune Checkpoint Blockade:: The Era of Oncodermatopathology

Advancements in cancer therapy with monoclonal immune checkpoint antibody blockade have impacted the practice of all medical specialties. Cutaneous immune-related adverse events (irAEs) are a frequent, unintended, off-target consequence of immune checkpoint inhibitor (ICI) therapy that have ushered in the era of oncodermatopathology. Knowledge of the diverse morphologic types of cutaneous irAEs from ICI therapy allows further classification of cutaneous irAEs according to major histopathologic reaction patterns. Early studies suggest that immune mechanisms of lichenoid dermatitis irAE, psoriasiform dermatitis irAE, and bullous pemphigoid irAE show some similarities and differences from their histopathologic counterparts not associated with ICI therapy.

Peritoneal melanosis associated with metastatic melanoma previously treated with targeted and immune checkpoint inhibitor therapy

Peritoneal melanosis is an uncommon benign condition, the pathophysiology of which is unclear. Macroscopically, it appears as diffuse dark brown or black pigmentation within the peritoneum, mimicking more sinister conditions such as metastatic melanoma. It has been described in a variety of contexts, but only exceedingly rarely in association with metastatic melanoma, with only two previous published case reports. We present a case of peritoneal melanosis associated with metastatic melanoma involving the spleen, previously treated with targeted and immune checkpoint inhibitor therapy. With increasing reports of melanoma regression manifesting as cutaneous tumorous melanosis in patients treated with immune checkpoint inhibitors, we postulate that, similarly, immunotherapy and tumour regression might have a role to play in the pathogenesis of the peritoneal pigmentation in this case.

Tumoral Melanosis in the Setting of Targeted Immunotherapy for Metastatic Melanoma-A Single Institutional Experience and Literature Review

BACKGROUND

Tumoral melanosis clinically resembles metastatic melanoma, occurs in the context of regressed disease, and requires evaluation to rule out underlying melanoma and metastatic disease. Histopathology demonstrates a nodular infiltrate of melanophages in the dermis, subcutaneous tissue, deep soft tissue, or lymph nodes in the absence of viable melanocytes. Recent limited reports of tumoral melanosis in the context of immunotherapy with ipilimumab (monoclonal antibody targeting CTLA-4) as well as nivolumab and pembrolizumab (humanized monoclonal antibodies against programmed death 1 receptor) highlight a unique presentation representative of treatment-related tumor regression and an association with a favorable clinical response.

OBJECTIVE

To describe our experience with tumoral melanosis in the setting of immunotherapy for metastatic melanoma and elucidate the clinical and histopathological features.

METHODS

Retrospective case series from a single tertiary care institution.

RESULTS

We describe 10 cases of patients with metastatic melanoma who received treatment with immunotherapy before the development of tumoral melanosis. Length of time between the initiation of therapy and the onset of tumoral melanosis ranged from 2 to 20 months with a mean time of 10 months. At the end of the follow-up period, 8 patients were classified as having a complete or partial response to treatment with immunotherapy. One patient had progression of visceral and cutaneous disease on ipilimumab despite developing tumoral melanosis, and 1 patient had yet to undergo repeat imaging. Furthermore, at the end of follow-up, 3 patients were alive with no evidence of active disease, 5 patients were alive with disease, and 1 patient was deceased, although this patient died of a cardiovascular event unrelated to his underlying melanoma. Of the patients who were classified as alive with disease, 2 patients had minimal remaining disease, and 2 patients had an almost complete response on immunotherapy with recurrence of visceral metastases after immunotherapy was discontinued. One patient developed new peritoneal and cutaneous metastases on pembrolizumab despite development of tumoral melanosis.

CONCLUSIONS

The underlying biologic mechanisms and prognostic implications of tumoral melanosis in the setting of immunotherapy remain to be elucidated. Further prospective studies with a larger cohort and prolonged follow-up are necessary to better understand the incidence, prevalence, and oncologic outcomes in patients with tumoral melanosis who receive immunotherapy.

Dermatologic toxicities to immune checkpoint inhibitor therapy: A review of histopathologic features

Antineoplastic agents that use the immune system have revolutionized cancer treatment. Specifically, implementation of immune checkpoint inhibitors, monoclonal antibodies that block cytotoxic T-lymphocyte-associated antigen-4, programmed cell death protein 1, or programmed cell death ligand 1 show improved and sustained responses in patients with cancer. However, these agents are associated with a plethora of adverse events, many manifesting in the skin. As the clinical application of cancer immunotherapies expands, understanding the clinical and histopathologic features of associated cutaneous toxicities becomes increasingly important to dermatologists, oncologists, and pathologists to ensure timely diagnosis and appropriate care. This review discusses cutaneous reactions to immune checkpoint inhibitors, focusing on histopathologic features.

Comparison of the Inflammatory Infiltrates in Tumoral Melanosis, Regressing Nevi, and Regressing Melanoma

BACKGROUND

Tumoral melanosis (TM) is a histologic diagnosis characterized by abundant pigment-laden macrophages in the dermis. It is generally thought to represent a regressed melanoma, although it has also been reported after benign pigmented lesions as well. Determining the antecedent lesion in cases of TM is of clinical importance to accurately guide therapy and prognostication. Comparing the histopathologic and immunohistochemical (IHC) characteristics of TM, halo nevi (HN), and regressing melanoma (RM) may help predict the antecedent lesion in cases of TM.

METHODS

Cases of TM, HN, and RM were selected and assessed for histopathologic (preservation of junctional melanocytic component, depth and width, solar elastosis, fibrosis, and preservation of rete ridge architecture) and IHC (SOX-10, CD138, and PD-1) parameters. PD-L1 immunostaining was also evaluated in cases of HN and RM.

RESULTS

Severe solar elastosis, fibrosis, and marked rete ridge effacement were more frequent in RM than in HN. By contrast, numerous plasma cells, clusters of lymphocytes expressing PD-1, and >50% PD-L1 expression in melanocytes were more common in HN than in RM. However, the association of these variables did not reach statistical significance.

DISCUSSION

Although studies with higher statistical power are needed, this study serves as an initial investigation to characterize the histopathologic and IHC characteristics, which may help better understand TM and its precursor lesions.

Pathology of immune-mediated tissue lesions following treatment with immune checkpoint inhibitors

Immune check point inhibitor (CPI) therapy has revolutionized treatment paradigms for several cancers, but at the cost of triggering a diverse spectrum of immune-mediated injury to non-cancer tissues. The complex biology of these toxicities remains incompletely understood, partly because tissue acquisition from affected areas can be challenging to retrieve, thus hindering development of targeted therapy. Here, we review the literature describing pathology of immune-mediated tissue lesions including gastrointestinal, skin, rheumatic, pulmonary, cardiac, renal and hepatic lesions and highlight key immunological insights.

Cutaneous tumoural melanosis: a presentation of complete regression of cutaneous melanoma

Partial regression is common in cutaneous melanoma; however, complete regression manifesting as tumoural melanosis is rare, conceptually challenging and under-reported. In this study we report on clinical, histological and molecular findings in four cases of completely regressed cutaneous melanoma with nodal or brain metastasis, followed by a comprehensive review of the literature. Our series included three women and one man with an average age of 60 years, and clinical presentation with hyper-pigmented cutaneous lesions. The main histological findings were expansile aggregates of melanophages with complete absence of malignant melanocytes on microscopic and immunohistochemical examination of the entire primary skin lesions, as well as substantial reduction in the number of junctional melanocytes in the overlying epidermis. NRAS mutant/BRAF wild type metastatic deposits were identified in three patients, with one patient having a BRAF V600E mutant metastatic tumour. Tumoural melanosis likely represents a partially effective immunological response to melanoma, with complete eradication of cutaneous disease and less effective systemic results. Patients with tumoural melanosis should be managed as potential completely regressed cutaneous melanoma, with comprehensive physical examination, imaging work up and close follow up.

Granulomatous Tumoral Melanosis Associated With Pembrolizumab Therapy: A Mimicker of Disease Progression in Metastatic Melanoma

Immune checkpoint inhibitor therapy has revolutionized the treatment of advanced melanoma, with these agents significantly improving survival for patients with metastatic disease. With the increasing use of these agents, the number of adverse reactions secondary to their use has also increased. Sarcoidosis and sarcoid-like reactions are one such immune checkpoint inhibitor-related adverse event. We report a case of sarcoid-like granulomatous tumoral melanosis in a patient on the programmed cell death-1 (PD-1) receptor inhibitor pembrolizumab for metastatic melanoma. This is, to our knowledge, the first reported case of a sarcoidal form of tumoral melanosis in a patient on anti-PD-1 therapy. We postulate that this reflects tumor regression in response to pembrolizumab-induced immune activation, with concomitant therapy-triggered induction of a sarcoid-like reaction. These findings and the literature review presented herein should alert clinicians and pathologists to the possibility of regressed lesions with sarcoid-like features presenting as mimickers of disease progression in patients undergoing immunotherapy for advanced melanoma.

Tumoral Melanosis Associated with Pembrolizumab-Treated Metastatic Melanoma

Tumoral melanosis is a form of completely regressed melanoma that usually presents as darkly pigmented lesions suspicious for malignant melanoma. Histology reveals dense dermal and subcutaneous infiltration of melanophages. Pembrolizumab is an antibody directed against programmed death receptor-1 (PD1) and is frontline treatment for advanced melanoma. An 81-year-old man with metastatic melanoma treated with pembrolizumab who developed tumoral melanosis at previous sites of metastases is described. The PubMed database was searched with the key words: antibody, immunotherapy, melanoma, melanosis, metastasis, pembrolizumab, and tumoral. The papers generated by the search and their references were reviewed. The patient was initially diagnosed with lentigo maligna melanoma on the left cheek three years earlier, and he was treated with wide local excision. The patient was subsequently diagnosed with epidermotropic metastatic malignant melanoma on the left parietal scalp 14 months later and was treated with wide local excision. Three months later, the patient was found to have metastatic melanoma in the same area of the scalp and was started on pembrolizumab immunotherapy. The patient was diagnosed with tumoral melanosis in the site of previous metastases nine months later. The patient remained free of disease 13 months after starting pembrolizumab. Tumoral melanosis may mimic malignant melanoma; hence a workup, including skin biopsy, should be undertaken. Extensive tumoral melanosis has been reported with ipilimumab, and we add a case following treatment with pembrolizumab. Additional cases of tumoral melanosis may present since immunotherapy has become frontline therapy for advanced melanoma. 

Diverse types of dermatologic toxicities from immune checkpoint blockade therapy

Immunomodulatory drugs that leverages host immune mechanisms to destroy tumor cells have been met with great promise in the treatment of cancer. Immunotherapy, targeting cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and the programmed cell death 1 (PD-1) receptor and its ligand (PD-L1) have shown tremendous improvements in the survival of patients with advanced solid tumors. However, the development of dermatologic toxicity (DT) is a consequence to immunotherapy. Review of published reports of the DT to immunotherapy revealed patients receiving anti-CTCLA-4 antibody or anti-PD-1/PD-L1 antibody often develop a DT of any type and grade. In this article, of the 3825 patients who were treated with anti-PD-1 and of 556 patients receiving anti-PD-L1, DT of any type and grade were reported in 1474 (∼39%) and 95 (∼17%) of patients, respectively. The emergence of specific types of DT to immunotherapy is beginning to be recognized can be categorized into four groups: (a) inflammatory, (b) immunobullous, (c) alteration of keratinocytes and (d) alteration of melanocytes. Lichenoid dermatitis and bullous pemphigoid appear to be DT more associated with anti-PD-1/PD-L1 antibody. The DT profile in patients receiving immunotherapy is diverse, and early recognition of specific types of DT that clinicians may encounter is critical for optimal patient care.