Epidermotropic primary neuroendocrine (Merkel cell) carcinoma of the skin with Pautrier-like microabscesses. Report of three cases and review of the literature

Merkel cell carcinoma: an update

Merkel cell carcinoma (MCC) is an uncommon primary cutaneous neuroendocrine carcinoma associated with an adverse prognosis. In recent years, our understanding of MCC biology has markedly progressed. Since the discovery of the Merkel cell polyomavirus, it has become clear that MCC represents an ontogenetically dichotomous group of neoplasms with overlapping histopathology. Specifically, most MCCs arise secondary to viral oncogenesis, while a smaller subset is the direct result of UV-associated mutations. The distinction of these groups bears relevance in their immunohistochemical and molecular characterization, as well as in disease prognosis. Further recent developments relate to the landmark utilization of immunotherapeutics in MCC, providing optimistic options for the management of this aggressive disease. In this review, we discuss both fundamental and emerging concepts in MCC, with a particular focus on topics of practical relevance to the surgical or dermatopathologist.

Merkel Cell Hyperplasia Versus Intraepidermal Merkel Cell Carcinoma: A Comparative Study of 2 Cases

ABSTRACT

Intraepidermal Merkel cell hyperplasia and Merkel cell carcinoma represent 2 histologically similar-appearing diagnoses with significant differences regarding prognosis and management. We present 1 case of each diagnosis to highlight characteristic histopathologic and immunohistochemical features. Our case of Merkel cell hyperplasia was identified by its small intraepidermal nest of monomorphic cells without atypia or mitoses, which demonstrated cytoplasmic, rather than perinuclear dot, patterning on CK20 staining. This can be contrasted with our case of intraepidermal Merkel cell carcinoma, which, despite a lack of dermal extension, demonstrated large nests of pleomorphic cells with frequent mitoses and apoptoses. The diagnosis was further confirmed by immunohistochemistry because CK20 staining showed classic perinuclear dot patterning. By presenting both diagnoses in parallel, this comparison aims to underscore crucial histopathologic and immunohistochemical similarities and differences.

Merkel Cell Carcinoma In Situ: No More Serendipity?

ABSTRACT

A 50-year-old man, with a history of extensive sun exposure and multiple previous non-melanoma skin cancers, presented with an asymptomatic 8-× 10-millimeter scaly, skin-colored papule on his right shoulder. Subsequent biopsy and excision revealed epidermal hyperplasia containing large atypical basaloid cells with pagetoid spread. Immunoperoxidase staining for cytokeratin-20 demonstrated a focal perinuclear dot-like pattern, and after excluding other in situ entities, a diagnosis of Merkel cell carcinoma In Situ (MCCIS) was rendered. MCCIS is a very rare entity. Although approximately 18% of Merkel cell carcinomas have epidermal involvement, currently only 17 cases of MCCIS have been reported, of which only 7 had no associated neoplasm. Previously, MCCIS was considered a serendipitous or incidental finding, as most cases co-existed with squamous cell carcinoma in situ. This case is unique in that it was not associated with a squamous lesion, and in addition, the pagetoid spread was unusual and has only occasionally been described. As such, MCCIS should be added to list of in situ epidermal lesions with pagetoid spread.

Dermal and Intraepidermal Merkel Cell Carcinoma With Squamous Cell Carcinoma: A Report of a Rare Case With Special Reference to the Touch Dome

ABSTRACT

In skin containing hair follicles, specialized epithelial structures known as "touch domes (TDs)" are located where the Merkel cells are clustered. We explored the histogenetic relationship between intraepidermal and dermal Merkel cell carcinomas (MCCs) and investigated which transformed progenitor cells can develop into intraepidermal MCC. We encountered an association between an extremely rare case of dermal and intraepidermal MCC with squamous cell carcinoma, which was examined using standard immunohistochemical methods with various epithelial, neuroendocrine, and TD markers including several immunohistochemical markers. Differential expression levels of CK20 and CD56 were found between intraepidermal and dermal MCCs, indicating molecularly distinct MCC populations. CK15 and CK17, expressed in TDs, were partially expressed in the intraepidermal neuroendocrine component at the tumor periphery in intraepidermal MCC with squamous cell carcinoma. These differences may suggest that the origin of dermal and intraepidermal MCCs is different under pathological conditions. We hypothesize that intraepidermal MCC is derived from tissue-specific stem cells localized within TDs.

Intraepidermal Merkel Cell Carcinoma Mimicking Melanoma in Situ: A Case Report

Merkel cell carcinoma (MCC) is an uncommon, but aggressive neoplasm with neuroendocrine differentiation that occurs on sun-damaged skin of the elderly. Because its clinical presentation is usually nonspecific, the diagnosis is often made after histopathologic evaluation. Most cases are intradermal. Epidermal involvement is uncommon, whereas MCC limited to the epidermis is extremely rare. Here, we describe a case of MCC in an 88-year-old man with an extraordinary histopathologic presentation, namely nested intraepidermal proliferation of neoplastic cells highly resembling melanoma in situ.

Merkel cell carcinoma of the forehead area: a literature review and case report

BACKGROUND

Merkel cell carcinoma (MCC) is an uncommon, aggressive malignancy of the skin, mostly affecting head and neck area in elderly white patients. Between head/neck sites, face accounts for 61% and forehead accounts for 17% of all face MCCs.

PURPOSE

We here present a literature review MCC cases arising in the forehead area, published in the English literature in the period 1987-2018, and report a personal observation with a late diagnosis and a treatment out of the current recommendations. The aims of this paper are to provide an up-to-date on MCC arising in the forehead area and to raise awareness about misdiagnosis of this type of lesion mimicking arteriovenous malformations (AVM).

MATERIAL AND METHOD

Literature review was performed on PubMed and Medline database and "Merkel cell carcinoma (MCC)," "forehead" and "MCC forehead location" were the terms the authors searched for. Patients' data have been drawn from descriptions of single cases and of short case series reports. For each case, data were collected about clinical characteristics, treatment modalities and outcomes. The study has been limited to the clinical features of the disease, excluding etiologic/pathogenic aspects.

RESULTS

Twenty-five patients with forehead MCC have been identified, coming from 20 sources. Nineteen presented a locoregional disease and 6 had an advanced pathology. TNM classification was reported in only two cases lacking for the other available data. Patients presented at mean age of 66 years with solitary or multiple nodules or dome-shaped/hemispherical mass, rarely ulcerated. Mean size of tumors was 1.13 cm of max diameter. Previous or concurrent malignancies or immune-hematologic disorders (AIDS) were often associated. At first investigation, lesion was often mistaken for other malignant or benign processes and, then, diagnosis was generally late. Some type of preoperative biopsy was performed in 3 patients, while the others had only a postoperative microscopic study of specimen. Initial treatment consisted in 6 cases (24%) in a not further specified about extent and width of margins local excision of the primary lesion, while a wide resection was reported in only 3 cases (12%). Surgical treatment of involved lymph-nodes was performed in 3 cases (12%). Six patients underwent radiotherapy for locoregional or distant recurrences. Mortality and overall survival rate at five years were 28% and 24%, respectively. Spontaneous regression was observed in 3 patients (12%).

CASE REPORT

Personal observation concerned an 82-year-old woman presenting with a forehead periorbital 5 × 5 cm red-bluish mass. The erythematous lesion was erroneously diagnosed as hemangioma on the base of color, the absence of any signs of malignancy, an angio CT indicating a hypervascular tissue and a FNA cytology (FNAC) lacking of malignant cells. The mass was excised as a benign lesion with about 1 cm margins extent without searching larger edges. Postoperative radiotherapy was offered to the patient after histology report, but she refused. After 4 months from surgery, she had a parotid metastasis and died from the illness in spite of platinum-based chemotherapy.

CONCLUSIONS

This study confirms the aggressiveness of forehead MCC, comparable with that of other face similar tumors. Personal case suggests that the deceitful benign feature of lesion may mimic an AVM and that FNAC may be misleading and diagnostic failure worsen prognosis. Our experience suggests that in the face smaller than 2-3 cm margins resection may increase the risk of locoregional recurrence. Therefore, postoperative wide-field irradiation should be ever delivered, after forehead MCC surgery, not only when clear margins are unattainable or involved with tumor, but also when negative microscopic edges are documented and residual cancer is thought not persist in the tumor bed. Orbit irradiation seems to be not dangerous for the eye.

In-transit recurrence of Merkel cell carcinoma associated with Bowen's disease: The first reported case successfully treated by avelumab

A 65-year-old Japanese man presented with a dome-shaped nodule, the base of which was contiguous with a dull brown plaque, on the left leg. After local excision of the cutaneous lesion and left inguinal lymph node dissection, several dermal and subcutaneous nodules developed successively on the left lower extremity. Hematoxylin-eosin staining of the primary cutaneous lesion demonstrated uniform neoplastic cells arranged in a trabecular pattern extending from the dermis to subcutis. Mitotic figures were abundant. Although the overlying epidermis was substantially intact, the Merkel cells had invaded the epidermis, resulting in Pautrier-like microabscesses. The hyperplastic epidermis adjacent to the nodule consisted of abnormally growing atypical keratinocytes. The enlarged left inguinal lymph node and successive secondary nodules contained Merkel cells similar to those in the primary nodule. Immunohistochemically, most tumor cells were positive for CAM5.2, synaptophysin, chromogranin A, CD56 and vimentin. The tumor cells in the left inguinal lymph node were positive for CAM5.2, synaptophysin and cytokeratin 20 but negative for CM2B4, and less than 1% of the cells expressed programmed cell death ligand 1. The patient was treated with avelumab, which showed significant efficacy against the in-transit recurrence. Two months later, all nodules had disappeared completely. We describe a case of in-transit recurrence of Merkel cell carcinoma that was associated histologically with Bowen's disease and was successfully treated with avelumab. Although accumulation of additional cases is needed, avelumab therapy may be a useful treatment for in-transit recurrence of Merkel cell carcinoma.

Merkel cell carcinoma arising in association with cutaneous T-cell lymphoma: A potential diagnostic pitfall

Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous neuroendocrine carcinoma with increased prevalence in patients with immunosuppression or B-cell neoplasms. To the best of our knowledge, an association with cutaneous T-cell lymphoma (CTCL) has not been previously described. In this report, we present two cases of MCC arising in the setting of CTCL. The first case was a female during her 70s with previously diagnosed stage IVA1 Sezary syndrome. Biopsy of a scaly patch showed two distinct abnormal cell populations. The first population consisted of hyperchromatic dermal and epidermotropic lymphocytes, expressing CD3 and CD4 with diminished CD7. The second population consisted of intraepidermal clusters of larger atypical cells that expressed synaptophysin, neurofilament, CK20, and Merkel cell polyomavirus transcript. The combination of findings was consistent with intraepidermal MCC in a background of CTCL. Excision showed residual intraepidermal MCC without dermal involvement. The second case was a male during his 50s with a longstanding history of mycosis fungoides, who presented with a new lesion on his right thigh. Biopsy and excision showed dermal MCC without secondary involvement by CTCL. Our cases show that MCC may rarely occur in the setting of T-cell lymphoma, and that intraepidermal MCC may mimic epidermotropic T-cells.

Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) encompasses neuroendocrine carcinomas primary to skin and occurs most commonly in association with clonally integrated Merkel cell polyomavirus with related retinoblastoma protein sequestration or in association with UV radiation-induced alterations involving the TP53 gene and mutations, heterozygous deletion, and hypermethylation of the Retinoblastoma gene. Molecular genetic signatures may provide therapeutic guidance. Morphologic features, although patterned, are associated with predictable diagnostic pitfalls, usually resolvable by immunohistochemistry. Therapeutic options for MCC, traditionally limited to surgical intervention and later chemotherapy and radiation, are growing, given promising early results of immunotherapeutic regimens.

Intraepidermal proliferation of Merkel cells within a seborrheic keratosis: Merkel cell carcinoma in situ or Merkel cell hyperplasia?

Intradepidermal proliferation of Merkel cells without any dermal component has been interpreted as either a hyperplastic process secondary to chronic ultraviolet radiation or a neoplastic process, namely Merkel cell carcinoma (MCC) in situ. The recent criteria that have been proffered to diagnose MCC in situ, unfortunately, are identical to those that have been applied to Merkel cell hyperplasia in the past, posing a diagnostic quandary when faced with an intraepidermal proliferation of Merkel cells. Most previously reported cases of MCC in situ have occurred within associated epithelial lesion that includes solar (actinic) keratosis and squamous-cell carcinoma in situ. Similarly, Merkel cell hyperplasia has been reported to occur in association with a variety of epithelial lesions as well as on chronically sun-damaged skin. Herein, a case of an intraepidermal proliferation of Merkel cells within a seborrheic keratosis is presented accompanied by a discussion on whether the proliferation represents another case of Merkel cell carcinoma in situ or an incidental hyperplastic process on chronically sun-damaged skin.

Update on Merkel Cell Carcinoma: Epidemiology, Etiopathogenesis, Clinical Features, Diagnosis, and Staging

Merkel cell carcinoma (MCC) is a rare, highly aggressive tumor, and local or regional disease recurrence is common, as is metastasis. MCC usually develops in sun-exposed skin in patients of advanced age. Its incidence has risen 4-fold in recent decades as the population has aged and immunohistochemical techniques have led to more diagnoses. The pathogenesis of MCC remains unclear but UV radiation, immunosuppression, and the presence of Merkel cell polyomavirus in the tumor genome seem to play key roles. This review seeks to update our understanding of the epidemiology, etiology, pathogenesis, and clinical features of MCC. We also review histologic and immunohistochemical features required for diagnosis. MCC staging is discussed, given its great importance in establishing a prognosis for these patients.

Cutaneous squamous and neuroendocrine carcinoma: genetically and immunohistochemically different from Merkel cell carcinoma

Cutaneous neuroendocrine (Merkel cell) carcinoma most often arises de novo in the background of a clonally integrated virus, the Merkel cell polyomavirus, and is notable for positive expression of retinoblastoma 1 (RB1) protein and low expression of p53 compared with the rare Merkel cell polyomavirus-negative Merkel cell carcinomas. Combined squamous and Merkel cell tumors are consistently negative for Merkel cell polyomavirus. Little is known about their immunophenotypic or molecular profile. Herein, we studied 10 combined cutaneous squamous cell and neuroendocrine carcinomas for immunohistochemical expression of p53, retinoblastoma 1 protein, neurofilament, p63, and cytokeratin 20 (CK20). We compared mutation profiles of five combined Merkel cell carcinomas and seven 'pure' Merkel cell carcinomas using targeted next-generation sequencing. Combined tumors were from the head, trunk, and leg of Caucasian males and one female aged 52-89. All cases were highly p53- and p63-positive and neurofilament-negative in the squamous component, whereas RB1-negative in both components. Eight out of 10 were p53-positive, 3/10 p63-positive, and 3/10 focally neurofilament-positive in the neuroendocrine component. Six out of 10 were CK20-positive in any part. By next-generation sequencing, combined tumors were highly mutated, with an average of 48 mutations per megabase compared with pure tumors, which showed 1.25 mutations per megabase. RB1 and p53 mutations were identified in all five combined tumors. Combined tumors represent an immunophenotypically and genetically distinct variant of primary cutaneous neuroendocrine carcinomas, notable for a highly mutated genetic profile, significant p53 expression and/or mutation, absent RB1 expression in the context of increased RB1 mutation, and minimal neurofilament expression.

New insights into merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare aggressive cutaneous malignancy of the elderly and immunocompromised populations. The clinical presentation of MCC is nonspecific, with the majority of cases presenting as localized skin involvement. Histologically and immunophenotypically, MCC is defined by both neuroendocrine and epithelial differentiation. Recently, the Merkel cell polyomavirus has been implicated in the pathogenesis of MCC. In addition, there have been numerous studies evaluating the histologic and immunohistochemical characteristics of MCC as they relate to diagnosis and prognosis. The purpose of this paper is to review the most salient and clinically relevant updates in the pathogenesis and histologic features of MCC. Specific attention is given to the clinical and histologic predictors of prognosis, staging, and the controversies concerning sentinel lymph node biopsy and therapy.

Basal cell carcinoma with progression to metastatic neuroendocrine carcinoma

Merkel cell carcinoma (MCC) or primary cutaneous neuroendocrine carcinoma is a malignant tumor considered to demonstrate differentiation towards Merkel cells that are present at the base of the epidermis or around the apical end of some hair follicles and are thought to play a yet uncertain role in sensory transduction. Here we present the case of a 54- year old female with a basal cell carcinoma (BCC) of the skin with neuroendocrine features (positivity for chromogranin) that has evolved during multiple recurrences and radiotherapy into a high-grade neuroendocrine carcinoma with morphological and immunohistochemical features of MCC (trabecular and nesting arrangement, positivity for chromogranin, cytokeratin 20, neuron specific enolase, and also neurosecretory granules on electron microscopy). The progression from a chromogranin positive basal cell carcinoma of the skin, to a high-grade neuroendocrine carcinoma demonstrates the potential for cross differentiation among skin tumors.

Merkel Cell Carcinoma with Pagetoid Spread

A case of Merkel cell carcinoma showing epidermotropism is presented. The neoplastic cells displayed dotlike immunoreactivity for cytokeratins and strong immunoreactivity for neuron-specific enolase. Although no neuroendocrine granules were found, characteristic paranuclear fibrous bodies were present.

High-grade neuroendocrine carcinoma presenting as an abscess: diagnosis by fine needle aspiration and review of the literature

Neuroendocrine carcinomas (NEC) comprise about 2% of all carcinomas. Review of the literature indicates only a few cases of NEC presenting as an abscess, all having been diagnosed by tissue biopsy. Here, we report the FNA diagnosis of a high-grade neuroendocrine carcinoma presenting as an abscess of the axilla/chest wall in a 68-year-old man and review the pertinent literature.

Merkel cell carcinoma frequently shows histologic features of basal cell carcinoma: a study of 30 cases

BACKGROUND

Merkel cell carcinoma (MCC) is a basaloid cutaneous neoplasm that may be mistaken for basal cell carcinoma (BCC).

METHODS

Thirty MCCs were examined for areas that histologically resembled BCC.

RESULTS

One of the histologic features of BCC (either a mucinous stroma or stromal artifactual retraction) was identified in all MCCs. A mucinous stroma was found in 28 MCCs (93%), stromal artifactual retraction in 27 (90%), mucin-containing gland-like spaces within tumor nests in 8 (27%), focal peripheral palisading in 8 (27%), epidermal involvement in 3 (10%) and dystrophic calcification in 1 MCC (3%). The cytologic features and absence of widespread peripheral palisading were the most reliable discriminators between MCC and BCC on routine sections. Squamous cell carcinoma was identified in four cases (13%). Two cases (7%) contained pagetoid intraepidermal spread (IES) of MCC. In one case, there was IES over the entire epidermal surface associated with intranuclear clearing, resembling the intranuclear cytoplasmic inclusions (INI) common in melanocytic tumors. INI were identified in six MCCs (20%).

CONCLUSIONS

MCCs frequently contain areas that histologically resemble BCC and other more common cutaneous malignancies. This can lead to diagnostic errors, particularly in small fragmented curettage specimens or frozen sections.

Merkel Cell Carcinomas

Merkel cell carcinoma (MCC) is a rare and extremely aggressive skin cancer that arises from primary neural cells. It presents most commonly in the elderly and immunocompromised patients. Pathologically, MCC should be distinguished from extrapulmonary small cell lung cancer or metastatic small cell lung cancer or a small cell variant of melanoma. The prognosis is based largely on the stage of disease at the time of presentation. Therapeutic options for MCC include wide resection with or without adjuvant radiotherapy or chemotherapy. Novel therapies based on the understanding of the molecular aspects of MCC are currently being explored.

The Toker Tumor

Primary neuroendocrine carcinoma of the skin is a relatively rare tumor that was first described by Cyril Toker in 1972. Since the seminal paper by Toker based on simple morphologic observations and detailed clinical correlation, our understanding of the clinical, morphological, and biological attributes of these lesions has grown exponentially with their increased awareness by pathologists and clinicians as well as with the many contributions of modern diagnostic techniques. The present review focuses principally on the various morphologic appearance that these tumors are able to adopt, the role of modern special techniques for diagnosis, and the conditions that need to be considered in their differential diagnosis.

Merkel cell carcinoma in organ-transplant recipients: report of two cases with unusual histological features and literature review

BACKGROUND

Non-melanoma skin cancers are the commonest malignancies after organ transplantation and are often associated with human papillomavirus (HPV). Merkel cell carcinoma is an uncommon neuroendocrine skin tumor, of which 67 cases have been reported up till now, usually briefly, in organ transplant patients.

METHODS

Among a cohort of 2340 organ-transplant recipients, two patients (one renal, one heart) developed cutaneous Merkel cell carcinomas 5 and 12 years of post graft, respectively. These were studied histologically and immunohistochemically, as well as virologically for the presence of HPV. A thorough literature review of all reported cases of Merkel cell carcinoma following solid organ transplantation was performed.

RESULTS

Despite a typical immunophenotype, the tumors showed unusual histological features: both were epidermotropic, and one was intermingled with a bowenoid squamous cell carcinoma. Search for HPV by immunohistochemistry and PCR proved negative in both cases.

CONCLUSION

In the setting of organ transplantation, Merkel cell carcinoma is much rarer than other non melanoma skin cancers but may show unusual histologic features. HPV do not seem to be involved in its pathogenesis.

Merkel cell carcinoma in situ

BACKGROUND

Merkel cell carcinoma (MCC) is a dermal small blue-cell tumor that occurs in the elderly on the sun damaged head and neck. Epidermal involvement is unusual and MCC limited to the epidermis is very rare.

CASE REPORT

A slightly tender pink hyperkeratotic papule was noted on the dorsal right hand of a 76-year-old man with a history of multiple skin cancers. An intraepidermal proliferation of small blue cells distributed in nests and single units at all levels of the epidermis was found within a solar keratosis and adjacent to an area of squamous cell carcinoma in situ. Cytokeratin 20 and neuron specific enolase highlighted these cells and failed to reveal dermal involvement. There was no residue on re-excision.

CONCLUSION

We report the third case of MCC in situ. These lesions have only been reported in association with squamous neoplasms on the extremities.

Primary neuroendocrine (Merkel cell) carcinoma of the skin: morphologic diversity and implications thereof

A significant proportion of primary neuroendocrine cell carcinomas of the skin (Merkel cell carcinomas [MCCs]) have been reported to occur in intimate association with malignant epithelial neoplasms, mainly squamous cell carcinomas. In addition, divergent differentiation within these tumors, particularly of squamous and eccrine types, is not infrequent. This expanded morphologic spectrum of MCC calls for evaluation of potential biologic implications of the phenotypic diversity and begs reconsideration of the histogenesis of the lesion. The current retrospective review of 29 cases of primary cutaneous neuroendocrine cell carcinoma aims to address these issues by integrating new information with that which is extant. Eleven tumors were associated with evolving or established cutaneous carcinomas: 2 actinic keratoses, 5 Bowen's disease, 3 superficial squamous cell carcinomas, and 1 basal cell carcinoma. Two combined squamous-neuroendocrine tumors occurred in recipients of solid organ transplants, and another developed in a Marjolin's ulcer at the site of a previous burn. Squamous and/or adnexal differentiation within the dermal component of the tumor was observed in 4 instances and was significantly associated with MCCs in intimate association with another cutaneous carcinoma. The outcome of the group as a whole is similar to that recorded in previous series of MCC, with local recurrence in 32% of cases and death caused by the neoplasm in 28%. Only 52% of the patients were alive with no history of metastasis at follow-up. No significant difference in outcome was observed between the patients with pure MCCs and those with MCCs in combination with another cutaneous carcinoma.

Merkel cell carcinoma of the skin and mucosa: report of 12 cutaneous cases with 2 cases arising from the nasal mucosa

BACKGROUND

Merkel cell carcinoma (MCC) is an uncommon skin tumor that most frequently arises on sun-exposed facial sites. It rarely occurs on mucous membranes of the head region. The primary MCC is usually treated by wide excision followed by radiation to the primary site and regional lymph nodes. Using traditional surgery the local recurrence rate ranges from 20 to 50%. In our clinic, Mohs surgery is used to excise the primary MCC completely, followed by radiation. Here we present our treatment experiences and outcomes.

OBJECTIVE

To document our experience of MCC treated by Mohs surgery. We present our series of 12 cases of MCC, 2 cases of which arose from mucosal sites of the nasal cavity.

METHODS

We reviewed 12 cases of MCC from the Mohs clinic database. We also reviewed the literature for cutaneous and mucosal MCC.

RESULTS

There were 12 cases of MCC: 10 cutaneous and 2 mucous. The site distribution of cutaneous MCC was eight on the head, one on the neck, and one on the groin. Of these, nine were treated by Mohs excision. Two patients developed local recurrence following Mohs treatment. The local recurrence rate was 22% (2 of 9). The sites of mucosal MCC were the nasal septum and nasopharynx. One case had a history of previous radiation and developed an MCC 40 years later. This case also demonstrated epidermotropic spread of Merkel cells to the overlying mucous epithelium. This patient required extensive intranasal and cranial surgery to remove the tumor. Both patients with mucosal MCCs died of their disease. The overall mucocutaneous survival of MCC at 1 year was 80% and at 2 years was 50%.

CONCLUSION

In our series, local control of the primary MCC was achieved in 70% of patients (7 of 10) using combined Mohs excision and radiation. Two recurrences had primary tumors larger than 3.5 cm in diameter, while the other case was nonresectable by Mohs surgery. Tumor size appeared to determine the degree of local control. When the postoperative Mohs defect was less than 3.0 cm in diameter, local and regional control appeared to be more favorable. When the primary facial MCC is relatively small, removal by Mohs surgery followed by radiation was effective, therapeutic, and less disfiguring. Mucosal MCC is rare and may occur as a long-term sequelae after radiation therapy to the skin.

Merkel cell carcinoma of the skin

BACKGROUND

Neuroendocrine/Merkel cell carcinoma (MCC) of the skin is an uncommon tumour. Currently, there are only limited data available on the natural history, prognostic factors, and patient management of MCC.

OBJECTIVES

To review our experience and build the largest database from the literature.

METHODS

Twenty-eight cases from the London Regional Cancer Center were combined with 633 cases obtained from the literature searched in English, French, German, and Chinese for the years 1966 to 1998. The database included age, sex, initial disease status at presentation to the clinic, site of primary, any coexisting disease, any previous irradiation, sizes of primary/nodal/distant metastases, management details, and final disease status. A new modified staging system was used: stage Ia (primary disease only, size > 2 cm), stage Ib (primary disease only, size > 2 cm); stage II (regional nodal disease), and stage III (beyond regional nodes and/or distant disease).

RESULTS

Age > 65 years, male sex, size of primary > 2 cm, truncal site, nodal/distant disease at presentation, and duration of disease before presentation (< or =3 months) were poor prognostic factors. Surgery was the initial treatment of choice and it significantly improved overall survival (p =.004).

CONCLUSIONS

We identified poor prognostic factors that may necessitate more aggressive treatment. The suggested staging system, incorporating primary tumour size, accurately predicted outcomes.

Intraepidermal Merkel cell carcinoma with no dermal involvement

Cutaneous Merkel cell carcinoma (MCC) typically involves the dermis. Less than 10% of MCC have epidermal involvement. Only one MCC confined exclusively to the epidermis has been previously reported but was not recognized until the lesion recurred with typical MCC in the dermis. We present a case of a wholly intraepidermal pagetoid MCC without dermal involvement in a 74-year-old man with a 2.0-cm solitary verrucous papule on the left index finger. The initial biopsy and complete excision specimens showed marked epidermal hyperplasia, focal prominent squamous cell atypia, and MCC with florid pagetoid spread through the epidermis. There was no evidence of tumor within the dermis. The pagetoid MCC tumor cells showed diffuse cytoplasmic staining with antibodies to cytokeratin 20, and negative staining for chromogranin, neurofilament, S-100, vimentin, HMB45, leukocyte common antigen, and CD3. The cell of origin of MCC is still debated. The existence of an entirely intraepidermal variant of MCC would lend support to the view that MCC is a neoplastic expression of Merkel cells in at least some cases. Dermal-based MCC is a high-grade primary cutaneous neoplasm, but MCC confined exclusively to the epidermis may have a better prognosis.

Cytokeratin 20: a marker for diagnosing Merkel cell carcinoma

Merkel cell carcinoma is an aggressive cutaneous neoplasm that is often difficult to diagnose because of its histologic and immunohistochemical similarity to metastatic oat cell carcinomas and other cutaneous neoplasms. Our purpose was to determine the utility of immunoperoxidase staining of cytokeratin 20 (CK 20), a newly discovered intermediate filament protein, in Merkel cell carcinomas and other cutaneous tumors. Sixty-one tumors were sectioned and stained with antibodies directed at CK 20. The staining of Merkel cell carcinomas was compared with metastatic oat cell carcinomas, lymphomas, squamous cell carcinomas, basal cell carcinomas, melanomas, metastatic carcinoids, spiradenomas, eccrine carcinomas, adenoidcystic carcinoma, sebaceous carcinomas, hidradenomas, sebaceous epitheliomas, trichoblastomas, mixed tumors, and metastatic adenocarcinomas. Nine of 10 Merkel cell carcinomas stained with antibody to CK 20. Two metastatic carcinomas to the skin were also positive. One hidradenoma and one squamous carcinoma exhibited focal staining, but were otherwise negative. All other tumors were nonstaining. Cytokeratin 20 is a sensitive and specific marker for Merkel cell carcinoma and is helpful in distinguishing between Merkel cell carcinoma and other malignant and benign neoplasms.

Pagetoid Merkel cell carcinoma: epidermal origin of the tumor

We report a case of intraepidermal Merkel cell carcinoma which occurred on the face of a 76-year-old white male. This slow-growing tumor was mostly confined in the epidermis and pilosebaceous apparatus where tumor cells spread in a pagetoid fashion forming tumor cell nests. Histologically it resembled a superficial spreading melanoma. A heavy lymphocytic infiltration was seen beneath the epidermal lesion as is often seen in pagetoid melanomas. Histochemical and ultrastructural features such as the presence of cytokeratin 20, synaptophysin, neuron specific enolase, desmosomes, and dense cored granules confirmed the diagnosis of Merkel cell carcinoma. Occasional mitotic cells and many apoptotic cells were found in the tumor. Dylon positive, amyloid depositions were seen in the lower epidermis and papillary dermis; they were probably derived from apoptotic tumor cells. It was thought that apoptosis limited the speed of growth of this tumor. We believe that this is probably the most convincing case of intraepidermal Merkel cell carcinoma originating from epidermal Merkel cells or its precursors (stem cells).

Localized limb cutaneous metastases

Cutaneous metastatic disease may be evident in a variety of forms and locations. Anatomically, it may on occasion be confined as localized limb metastases. We report on two patients with localized limb metastases, one from melanoma and the other from Merkel cell carcinoma. Patients with localized limb metastasis have a poor prognosis; however, treatment options not available for generalized cutaneous metastatic disease, such as amputation or isolated limb perfusion with chemotherapeutic agents, can be at times be beneficially employed.

Merkel cell carcinoma: analysis of clinical, histologic, and immunohistologic features of 132 cases with relation to survival

BACKGROUND

Merkel cell carcinoma (MCC) is an uncommon malignancy of the skin and has a high rate of recurrence and metastasis. There have been few large studies of the biologic behavior of MCC.

OBJECTIVE

Our purpose was to determine whether there were clinical or histologic features of MCC that predict its biologic behavior.

METHODS

We reviewed 132 cases of MCC. Clinical and histologic features were correlated with follow-up information to determine whether any of these were associated with prognosis.

RESULTS

Clinical information was available on 126 patients; 57 were alive, 1 was alive with tumor, 28 died of tumor, 27 died from other causes, and 14 were lost to follow-up. MCC on the buttock/thigh area or trunk had the worst prognosis, and those on the distal extremities had the best prognosis; however, the difference was not statistically significant. Sex and age were not significant factors. Small cell size, high mitotic rate, and large tumor size were associated with a low survival rate. When cell size was excluded, male sex and depth of invasion were associated with a worse survival, although these were not statistically significant.

CONCLUSION

Cell size, mitotic rate, and tumor size are significant factors in relation to the biologic behavior of MCC.

Epidermotropically metastatic breast carcinomas. Rare histopathologic variants mimicking melanoma and Paget's disease

Epidermotropic metastases from internal malignancies are exceedingly rare. We report two examples of epidermotropic metastatic breast carcinoma with striking intraepidermal involvement. The first case mimicked melanoma because the neoplastic cells contained melanin and were disposed both as single units and as nests at the dermoepidermal junction and throughout the epidermis. In the second case, the neoplastic cells were seen as isolated neoplastic cells with large, pale cytoplasm scattered throughout the epidermis, closely resembling extramammary Paget's disease. Immunohistochemical studies in both cases demonstrated the epithelial nature of intraepidermal neoplastic cells, which showed an immunophenotype identical to the neoplastic cells present in the dermis: positive staining with anti-cytokeratins, CEA, EMA, and GCDFP-15 and negative with anti-S-100 protein and HMB-45. These findings ruled out the possibility of a collision lesion, or simultaneous occurrence of melanoma and metastatic breast carcinoma. Pagetoid intraepidermal spread of metastatic breast carcinoma, as in our two cases, is exceptional. We also discuss the histogenetic similarities between our findings and those of mammary and extramammary Paget's disease, as well as the differential diagnosis of other cutaneous disorders characterized by pagetoid intraepidermal spread of neoplastic cells.

Merkel cell carcinoma. Diagnosis and treatment

BACKGROUND

Merkel cell carcinoma is an uncommon malignancy of the skin that often portends a poor prognosis. Since its first description by Toker in 1972, a plethora of case reports and articles regarding the etiopathogenesis and treatment have been published spanning multiple medical and surgical disciplines. Much confusion still exists regarding the diagnosis and treatment of this ominous tumor.

OBJECT

Through extensive review of the medical, surgical, and pathological literature, to collate the observations of multiple investigators and summarize these findings.

METHODS

Articles from journals of multiple subspecialties were carefully reviewed with particular emphasis placed on epidemiology, prognosis, histology, immunohistochemistry, electron microscopy, tumor origin, treatment, and work-up of Merkel cell carcinoma.

RESULTS

Merkel cell carcinoma is an aggressive malignant neoplasm. Local recurrence develops in 26-44% of patients despite therapy. Up to three-fourths of patients eventually develop regional nodal metastases with distant metastases occurring in one-third of all patients. Reported overall 5-year survival rates range from 30% to 64%.

CONCLUSION

Treatment recommendations unfortunately are based more on anecdotal than scientific data because of the rarity of the tumor and its recognized high risk. Most authors recommend wide local excision of the primary lesion and regional lymph node resection if lymph nodes are palpable followed by x-irradiation of both the postsurgical bed and lymph node basin. The role of elective lymph node resection in the absence of clinically positive nodes remains controversial.

Merkel cell carcinoma

Merkel cell carcinoma is a malignant neuroendocrine tumor with features of epithelial differentiation. Biologically aggressive, it may be difficult to diagnose and, particularly in its late stages, even more difficult to treat effectively. This article addresses what is known and what is still controversial about the histogenesis, diagnosis, and management of Merkel cell carcinoma and the structure and function of the Merkel cell from which it is believed to be derived. The incidence, clinical presentation and diagnosis, ultrastructure, immunocytochemistry, treatment, and prognosis of this tumor will be discussed.

Neuroendocrine carcinoma of the skin (Merkel cell carcinoma) in a black

Neuroendocrine carcinoma of the skin is an uncommon, small-cell neoplasm most commonly found on white, sun-exposed skin. Diagnosis by clinical and histologic means may be difficult. Immunohistochemical and ultrastructural analysis are often required. Because of the aggressive nature of neuroendocrine carcinoma of the skin, prompt diagnosis and treatment are essential. We present the rare occurrence of a neuroendocrine carcinoma of the skin on sun protected skin in a black. Clinical, histologic, immunohistochemical, and ultrastructural features are reviewed, and therapeutic options are discussed.

Epidermotropic neuroendocrine carcinoma. Immunohistochemical differentiation from simulators, including malignant melanoma

Epidermotropic neuroendocrine carcinoma (NEC) is rare. Based on such a case in an 88-year-old woman with a facial NEC showing epidermotropism with a pagetoid growth pattern, we asked whether several similar tumors involving the epidermis could be easily differentiated by immunohistochemical methods. We constructed a panel of control cases (2 each) for NEC, clear cell Bowen's disease (CCBD), Paget's disease (PD), superficial basal cell carcinoma (SBCC), cutaneous T-cell lymphoma (CTTL), and superficial spreading malignant melanoma (SSMM) to compare with our patient. A panel of antibodies including epithelial membrane antigen (EMA), neuron specific enolase (NSE), AE1/3 cytokeratin (CK), carcinoembryonic antigen (CEA), leukocyte common antigen (LCA), S-100, and HMB-45 were applied. Cutaneous NEC controls and our patient's tumor were strongly positive for EMA and NSE and had paranuclear dot-like cytoplasmic positivity for CK. CCBD was moderate to strong for CK. PD was strong for CEA. SBCC was essentially negative for all. CTLL was strong for LCA. SSMM was strong for S-100 and HMB-45. Controls were either negative or weak for the antibodies not mentioned. We conclude that this antibody panel can reliably differentiate these epidermotropic or juxtaepidermal tumors in diagnostic dermatopathology and should be applied to lesions requiring separation beyond H & E capabilities, especially with superficial shave biopsies showing small cell "Pagetoid" growth patterns.

Merkel cell carcinoma of the head and neck associated with Bowen's disease

The Merkel cell carcinoma occurs primarily in the skin of the head and neck, and develops in the dermis with a trabecular growth pattern. Immunohistochemistry reveals positive staining for neuron-specific enolase, neurofilaments, cytokeratin and chromogranin A. Electron microscopically, the tumor cells contain dense-core granules, spinous cytoplasmic processes, desmosomes, zonulae adherentes and paranuclear filament aggregates besides frequent mitoses, focal necroses and lymphocyte and plasma cell infiltrates. The Merkel cell carcinoma is often co-existent with other malignancies such as squamous cell carcinoma or, as in the present study, with Bowen's disease. The definite diagnosis of the Merkel cell carcinoma can be effected only by electron microscopic examination of the tumor.

The Merkel cell and associated neoplasms in the eyelids and periocular region

Merkel cells are clear oval cells in the epidermis and outer root sheaths of hair follicles, which are probably of epithelial origin, share ultrastructural features with neuroendocrine cells, and are found in association with touch receptors. In the eyelid, they occur singly in the epidermis and external root sheaths of hairs and eyelashes, and in specialized touch spots alternating with eyelashes. Their typical electron microscopical and antigenic features include dense-core granules, intranuclear rodlets, spinous processes, and a positive reaction for specific cytokeratins, epithelial membrane antigen, neuron-specific enolase, chromogranin and synaptophysin. Merkel cell carcinoma probably develops from precursor cells which give rise to keratinocytes and Merkel cells, and nearly one out of ten Merkel cell carcinomas occur in the eyelid and periocular region. They tend to be bulging lesions near the lid margin of elderly patients, reddish in color, and erythematous with telangiectatic vessels. The diagnosis is based on the frequent presence of neurofilaments and paranuclear aggregates of intermediate filaments in addition to features typical of normal Merkel cells. The tumor often mimics lymphoma or undifferentiated carcinoma and frequently invades lymphatic vessels. One third of Merkel cell carcinomas recur, almost two thirds give rise to regional node metastases, and up to one half metastasize widely and result in death. Initial treatment should be prompt and aggressive, with wide resection and routine postoperative irradiation. Although metastatic lesions often respond to radiation therapy and cytostatic drugs, these treatments are mainly of palliative value.

Incidence of cutaneous T cell lymphoma and other rare skin cancers in a defined population

Between 1970 and 1984 in Rochester, Minnesota, rare skin cancers developed in 15 local residents: cutaneous T cell lymphoma (six subjects), dermatofibrosarcoma protuberans (four), adenocarcinoma of sweat glands (two), Merkel cell carcinoma (one), liposarcoma (one), and extramammary Paget's disease (one). These cases were identified through a unique computerized retrieval system that is maintained at the Mayo Clinic for the population of Rochester, Minnesota. The annual incidences of these cancers in the Rochester population were 0.9, 0.5, 0.3, 0.2, 0.2, and 0.2 per 100,000 residents, respectively (standardized to 1980 U.S. population). To our knowledge, this is the first report of the incidences of these rare skin cancers in a well-defined population.

Sézary syndrome: diagnosis, prognosis, and critical review of treatment options

Sézary syndrome is a form of leukemia-lymphoma characterized clinically by erythroderma, pruritus, adenopathy, and circulating atypical cells with cerebriform nuclei. Histologically, atypical lymphocytes in the dermis and Pautrier's microabscesses are often present in skin biopsy specimens. Immunologic findings that support a diagnosis of Sézary syndrome include a predominance of CD4+ lymphocytes in both skin biopsy specimens and peripheral blood. Cytogenetic studies that demonstrate aneuploidy and DNA probe analysis that shows gene rearrangement for the beta-subunit of the T cell receptor are the latest, most sensitive, and specific methods for identifying the clonal nature of the disease. Various staging systems are used. We review the various treatments for Sézary syndrome, including the newer, biologically based investigational therapies, (e.g., antithymocyte globulin, monoclonal antibodies and other immunostimulants, retinoids, cyclosporine, interferon, and extracorporeal photopheresis). Extracorporeal photopheresis and some chemotherapeutic agents appear to produce the best results in terms of response and remission duration with minimal toxicity. However, more multicenter controlled clinical trials are needed to determine the most effective single or combined therapeutic regimen.

What's new in dermatopathology

This article reviews the recent English language literature on dematopathology, with an emphasis on publications appearing between January 1986 and July 1987. Immunohistochemistry continues to grow in importance as a diagnostic as well as a research technique. The advent of in situ deoxyribonucleic acid hybridization technology has raised diagnostic accuracy to a new level; it has already proved valuable in the diagnosis of certain viral infections. Areas that have received particular attention include phenotypic characteristics of lymphomas and lymphoma-like conditions, congenital melanocytic nevi and malignant melanoma, neuroendocrine carcinoma and other small cell tumors of the skin, sweat gland carcinomas, and eosinophil and its associated diseases, and unusual infectious diseases involving the skin.

[Clinical aspects and therapy of Merkel cell tumor--report of 4 personal cases and review of the literature]

Four cases of Merkel cell tumor located in the face or on the trunk are presented. In a literature review 339 cases were found and analysed. The Merkel cell tumor is a neuroendocrine tumor of the skin derived from the Merkel cells. It is located most often in the face and neck area. Typically, it is an exophytic node, has a red-blue color and measures 25 mm in diameter on the average. Since it is metastasizing it is a malignant tumor. Regional node metastases were found in 27%, local recurrences occur in 51%, and distant metastases were seen in 32% of the cases. The best therapy is excision with wide margins as is the rule for a malignant skin tumor. While the tumor reacts to radiotherapy, chemotherapy seems to be of no help.