Low-Grade Neuroendocrine Carcinoma of the Skin (Primary Cutaneous Carcinoid Tumor) as a Distinctive Entity of Cutaneous Neuroendocrine Tumors: A Clinicopathologic Study of 3 Cases With Literature Review

Recurrent GATA3 P409Afs*99 Frameshift Extension Mutations in Sweat-gland Carcinoma With Neuroendocrine Differentiation

Sweat-gland carcinoma with neuroendocrine differentiation (SCAND) was recently proposed as a new cutaneous adnexal neoplasm with neuroendocrine differentiation; however, its genetics are not well known. Herein, we performed clinicopathologic and genetic analyses of 13 SCAND cases and 5 control cases of endocrine mucin-producing sweat gland carcinoma (EMPSGC). The SCAND group included 11 males and 2 females with a median age of 68 years (range, 50 to 80 y). All SCAND lesions occurred in the ventral trunk or genital area. Of the 13 SCAND cases, 9 and 5 exhibited lymph node and distant metastases, respectively. Three (23.1%) patients with SCAND died of the disease. In contrast, neither metastasis nor mortality was confirmed in the EMPSGC cases. Immunoexpression of the androgen receptor, c-Myb, and MUC2 was limited in SCAND, whereas EMPSGC frequently expressed these immunomarkers. GATA3 P409Afs*99 extension mutations were detected in 7 (53.8%) of the 13 SCAND cases, using Sanger or panel sequencing. All 7 SCAND cases with GATA3 mutations were located in the genital, inguinal, or lower abdominal regions, whereas 5 of the other 6 SCAND cases were located in the anterior upper to mid-trunk. No GATA3 mutations were detected in the EMPSGC cases (0/5, 0%). These clinicopathologic and genetic findings support SCAND as a tumor entity distinguishable from EMPSGC. In addition, the characteristic frameshift extension mutations in GATA3 contribute to the establishment of the tumor-type concept of SCAND.

Case of primary low-grade neuroendocrine carcinoma of the skin

A man presents a 4 mm skin tumour at his general practitioner. The tumour is removed on the suspicion of a dermatofibroma. Important differential diagnoses are sebaceous neoplasms, melanomas, Merkel cell carcinomas and large cell neuroendocrine carcinoma, and metastases of neuroendocrine neoplasms from the gut or lung. Immunohistochemical staining excluded sebaceous neoplasm, melanoma and Merkel cell carcinoma, however, was positive for multiple neuroendocrine markers. Relevant scans showed no signs of a primary tumour anywhere else. The final diagnosis was a primary low-grade neuroendocrine carcinoma of the skin. At 30 months follow-up, there was no sign of recurrence.

Primary high-grade neuroendocrine carcinoma with positive steroid hormone receptors arising in the inguinal skin: A case report of An exceedingly rare entity

INTRODUCTION

Neuroendocrine tumors usually arise from the gastrointestinal and pulmonary tracts and rarely from the skin. We report a unique case of high-grade neuroendocrine carcinoma with positive steroid hormone receptors in the primary skin of the groin.

CASE PRESENTATION

A 79-year-old female presented with a lump in her left inguinal region for 15 years that grew gradually. The tumor cells were arranged in sheets, solid nests, and bands within a rich network of thin-walled capillaries. Mucin was abundant in the stroma, and the tumor cells exhibited high-grade lesions, significant necrosis, and frequent mitosis, with small scattered foci of low-grade components. Immunohistochemistry revealed that the tumor cells diffusely and strongly expressed cytokeratin, synaptophysin, chromogranin A, GATA3, CAM5.2, and estrogen and progesterone receptors; partially expressed AR and GCDFP15.

DIAGNOSIS

Based on pathological morphology, and immunohistochemical staining, it was confirmed as Primary high-grade neuroendocrine carcinoma with positive steroid hormone receptors arising in the inguinal skin. The patient underwent resection of the inguinal tumor and left inguinal lymph node dissection.

INTERVENTIONS

The patient has been followed up for 16 months and has not undergone further examinations or received additional treatment. There is no evidence of tumor recurrence at the site of the original surgical resection, and the patient general condition is satisfactory.

CONCLUSIONS

The morphology of this tumor is unique and previously unreported, further expanding the possible pathogenesis and histological morphologies of this tumor type.

Primary Cutaneous Neuroendocrine Tumor of the Vulva: A Case Report

Primary cutaneous neuroendocrine tumors (CNET) are extremely rare. Only a few cases have been reported so far. CNET have an indolent clinical course and usually present as a single flesh-colored nodule with a predilection for the scalp and trunk in elderly patients. While primary CNET have characteristic histological and immunohistochemical features akin to other low-grade neuroendocrine tumors elsewhere in the body, diagnosing these tumors on skin biopsies can be challenging as they are particularly mistaken for other, more commonly diagnosed, entities. In the current report we present a unique case of primary CNET of the vulva. The clinical presentation will be discussed as well as the histopathologic and immunohistochemical features and most importantly the possible pitfalls in microscopic examination.

The Complex Histopathological and Immunohistochemical Spectrum of Neuroendocrine Tumors-An Overview of the Latest Classifications

Neuroendocrine neoplasms (NENs) originate from the neuroendocrine cell system, which may either take the shape of organoid cell aggregations or be composed of dispersed cells across various organs. Therefore, these tumors are heterogenous regarding the site of origin, functional status, degree of aggressiveness, and prognosis. When treating patients with neuroendocrine tumors, one of the most significant challenges for physicians is determining the correct tumor grade and thus classifying patients into risk categories. Over the years, the classification of these tumors has changed significantly, often causing confusion due to clinical, molecular, and immunohistochemical variability. This review aims to outline the latest NENs classifications regardless of their site of origin. Thus, an overview of the key histopathological and immunohistochemical characteristics of NENs could pave the way to validate possible predictive and prognostic markers and also guide the therapeutic conduct.

Sweat Gland Carcinoma With Neuroendocrine Differentiation of the Areola as a Potential Clinicopathologic Mimicker of Male Breast Carcinoma and Syringocystadenocarcinoma Papilliferum

ABSTRACT

Sweat gland carcinoma with neuroendocrine differentiation (SCAND) is a newly proposed tumor entity of primary cutaneous apocrine/eccrine adnexal tumor with neuroendocrine differentiation. The histopathologic variations are not yet well known. In this article, we present a case of SCAND mimicking male breast cancer and syringocystadenocarcinoma papilliferum. A 68-year-old man presented with a reddish 12-mm nodule on his left areola. No lymph node or distant metastases were observed. The patient was disease free 1 year and 9 months after the tumor was surgically resected but died of cerebral hemorrhage. Histopathological examination revealed a predominantly intradermal tumor with marked syringotropism, mimicking a component of mammary ductal carcinoma in situ. In addition, another tissue section displayed a cup-shaped papillated tumor with syringocystadenocarcinoma papilliferum-like features, which were also seen because of marked syringotropism. Diffuse immunoexpression of cytokeratin 7, cytokeratin 19, chromogranin A, synaptophysin, INSM1, estrogen receptor, carcinoembryonic antigen, epithelial membrane antigen, and GATA3 was observed in the tumor, but no BRAF immunoexpression was seen. The present case would help us to understand the histopathological variation and differential diagnosis of SCAND. The histopathological diagnosis of male breast cancer or syringocystadenocarcinoma papilliferum should be made by ruling out SCAND.

Large Cell Neuroendocrine Carcinoma of the Skin/Conjunctiva: A Series of 6 Cases including 1 Combined Case With Squamous Cell Carcinoma

ABSTRACT

This study sought to reveal the clinicopathologic characteristics of large cell neuroendocrine carcinoma (LCNEC) of the skin/conjunctiva. The retrieved patients included 3 men and 3 women with a median age of 85 (63-95) years. All lesions occurred on the face, including the ears, with a median tumor size of 11.5 (7-65) mm. Lymph node metastasis was observed in 5 (83%) of 6 cases, and distant metastasis was noted in 2 (33%). One patient (17%) who had a 13-mm-sized tumor died of the tumor 13 months after excision. All tumors were mainly located in the dermis, and one of them also exhibited intraepithelial spreading. The cytology resembled that of an LCNEC in other organs. No adnexal differentiation was observed. Five cases were of the pure type, but one had a component of squamous cell carcinoma. Immunoreactivities for CAM5.2, CK7, CK19, BerEP4, epithelial membrane antigen, neuron-specific enolase, synaptophysin, c-KIT, GATA3, and bcl-2 were frequently present, but CK20, neurofilament, Merkel cell polyomavirus large T antigen, mammaglobin, estrogen receptor, HER2, and TTF1 were completely negative in all cases. Mutant-pattern immunostaining of p53, PTEN, and Rb was frequently observed. The Ki67 rate exceeded 70% in all cases. LCNEC of the skin/conjunctiva is a morphologically-defined group of primary cutaneous/conjunctival neuroendocrine neoplasm, although it may be heterogeneous similar to other-site LCNEC or Merkel cell carcinoma. This study highlighted the predominant location for the face, high metastatic and lethal potential, possible combination with other tumor components, and frequent mutant-type immunoexpressions of p53, PTEN, and Rb in this tumor group.

Investigation of the RB1-SOX2 axis constitutes a tool for viral status determination and diagnosis in Merkel cell carcinoma

MCC (Merkel cell carcinoma) is an aggressive neuroendocrine cutaneous neoplasm. Integration of the Merkel cell polyomavirus (MCPyV) is observed in about 80% of the cases, while the remaining 20% are related to UV exposure. Both MCPyV-positive and -negative MCCs-albeit by different mechanisms-are associated with RB1 inactivation leading to overexpression of SOX2, a major contributor to MCC biology. Moreover, although controversial, loss of RB1 expression seems to be restricted to MCPyV-negative cases.The aim of the present study was to assess the performances of RB1 loss and SOX2 expression detected by immunohistochemistry to determine MCPyV status and to diagnose MCC, respectively.Overall, 196 MCC tumors, 233 non-neuroendocrine skin neoplasms and 70 extra-cutaneous neuroendocrine carcinomas (NEC) were included. SOX2 and RB1 expressions were assessed by immunohistochemistry in a tissue micro-array. Diagnostic performances were determined using the likelihood ratio (LHR).RB1 expression loss was evidenced in 27% of the MCC cases, 12% of non-neuroendocrine skin tumors and 63% of extra-cutaneous NEC. Importantly, among MCC cases, RB1 loss was detected in all MCPyV(-) MCCs, while MCPyV( +) cases were consistently RB1-positive (p < 0.001). SOX2 diffuse expression was observed in 92% of the MCC cases and almost never observed in non-neuroendocrine skin epithelial neoplasms (2%, p < 0.0001, LHR +  = 59). Furthermore, SOX2 diffuse staining was more frequently observed in MCCs than in extra-cutaneous NECs (30%, p < 0.001, LHR +  = 3.1).These results confirm RB1 as a robust predictor of MCC viral status and further suggest SOX2 to be a relevant diagnostic marker of MCC.

Recent Advances on Immunohistochemistry and Molecular Biology for the Diagnosis of Adnexal Sweat Gland Tumors

Simple Summary

Cutaneous sweat gland tumors form an extremely diverse and heterogeneous group of neoplasms that show histological differentiation to the sweat apparatus. Due to their rarity, wide diagnostic range, and significant morphological overlap between entities, their accurate diagnosis remains challenging for pathologists. Until recently, little was known about the molecular pathogenesis of adnexal tumors. Recent findings have revealed a wide range of gene fusions and other oncogenic factors that can be used for diagnostic purposes and, for some, can be detected by immunohistochemistry. Among other organs containing exocrine glands, such as salivary glands, breasts, and bronchi, most of these biomarkers have been reported in homologous neoplasms that share morphological features with their cutaneous counterparts. This review aims to describe these recent molecular and immunohistochemical biomarkers in the field of sweat gland tumors.

Abstract

Cutaneous sweat gland tumors are a subset of adnexal neoplasms that derive or differentiate into the sweat apparatus. Their great diversity, rarity, and complex terminology make their pathological diagnosis challenging. Recent findings have revealed a wide spectrum of oncogenic drivers, several of which are of diagnostic interest for pathologists. Most of these molecular alterations are represented by gene fusions, which are shared with other homologous neoplasms occurring in organs containing exocrine glands, such as salivary and breast glands, which show similarities to the sweat apparatus. This review aims to provide a synthesis of the most recent immunohistochemical and molecular markers used for the diagnosis of sweat gland tumors and to highlight their relationship with similar tumors in other organs. It will cover adenoid cystic carcinoma (NFIB, MYB, and MYBL1 fusion), cutaneous mixed tumor (PLAG1 fusion), cylindroma and spiradenoma and their carcinomas thereof (NF-κB activation through CYLD inactivation or ALKP1 hotspot mutation), hidradenoma and hidradenocarcinoma (MAML2 fusion), myoepithelioma (EWSR1 and FUS fusion), poroma and porocarcinoma (YAP1, MAML2, and NUTM1 fusion), secretory carcinoma (ETV6, NTRK3 fusion), tubular adenoma and syringo-cystadenoma papilliferum (HRAS and BRAF activating mutations). Sweat gland tumors for which there are no known molecular abnormalities will also be briefly discussed, as well as potential future developments.

Sweat-gland carcinoma with neuroendocrine differentiation (SCAND): a clinicopathologic study of 13 cases with genetic analysis

Low-grade neuroendocrine carcinoma of the skin (LGNECS) was proposed in 2017 as a new primary cutaneous neoplasm with neuroendocrine differentiation; however, it is not yet well known due to its rarity. Herein, we perform a detailed clinicopathologic analysis of 13 cases as well as panel DNA sequencing in three cases. The study included 12 males and 1 female with a median age of 71 (43-85) years. All lesions occurred on the ventral trunk. The mean tumor size was 2.2 (0.8-11.0) cm. The histopathology resembled that of well-differentiated neuroendocrine tumors (NETs) in other organs, but intraepidermal pagetoid spreading was seen in 8 (61.5%) cases and stromal mucin deposits in 4 (30.8%). Immunoreactivity for CK7, CK19, EMA, BerEP4, CEA, chromogranin A, synaptophysin, INSM1, GCDFP15, GATA3, ER, and bcl-2 were present in varying degrees in all tested cases. PTEN c.165-1G>A splice site mutation was detected by panel sequencing in one case, and GATA3 P409fs*99 and SETD2 R1708fs*4 in another case. Lymph node metastasis was seen significantly in cases with tumor size >2.0 cm [8/8 (100%) vs. 1/5 (20%)]. All three cases with size >3.0 cm were in unresectable advanced-stage [3/3 (100%) vs. 1/10 (10%)], and two of the three patients succumbed to the disease. The two cases of death revealed mild nuclear atypia (mitosis: 1/10 HPFs) and moderate nuclear atypia (2/10 HPFs). Thus, tumor size would be a better prognostic factor than nuclear atypia, mitotic count, and Ki67 index, unlike in NETs. These clinicopathologic and immunohistochemical features would represent the characteristics as skin adnexal tumors with apocrine/eccrine differentiation rather than NETs; therefore, we rename it as sweat-gland carcinoma with neuroendocrine differentiation (SCAND).

Case of low-grade neuroendocrine carcinoma of the skin presenting metastases to lymph nodes and peritoneum

A 61-year-old Japanese man had a gradually growing, red-colored nodule in his umbilicus from 3 years ago. He had no symptoms such as hot flush, diarrhea or wheezing. Computed tomography detected a 3.0 cm × 3.0 cm enhanced nodule on the umbilical portion, inguinal and axillary lymph node swelling, and peritoneal nodules. Upper and lower gastrointestinal endoscopy and cystoscopy did not show any other tumor. We resected the umbilical nodule and subjected the inguinal lymph node and peritoneal nodule to biopsy. Histopathological findings indicated that the cutaneous lesion was composed of variously sized nests that included small, monomorphic, round to polygonal cells, mainly in the dermis to the peritoneum. Mitotic figures were scant. The inguinal lymph node and peritoneal nodule were positive for metastasis. Immunohistochemistry was diffusely positive for cytokeratin (CK)-7, CD56, chromogranin A, synaptophysin, estrogen receptor-α, progesterone receptor, GATA3 and carcinoembryonic antigen, and focally positive for mammaglobin and gross cystic disease fluid protein 15. The Ki-67 labeling index was 1.5%. The patient was diagnosed with a case of low-grade neuroendocrine carcinoma of the skin (LGNECS) occurring on the umbilicus. This case exhibited distant peritoneal metastasis, as well as inguinal and axillary lymph node metastases; however, the patient is alive without chemotherapy at 23 months after the first visit. LGNECS is a newly proposed, extremely rare entity that has been reported under various names, including primary cutaneous carcinoid tumor. In the present case, this tumor shows a slow-growing nature and favorable prognosis, even though it harbors metastatic potential.

A common classification framework for neuroendocrine neoplasms: an International Agency for Research on Cancer (IARC) and World Health Organization (WHO) expert consensus proposal

The classification of neuroendocrine neoplasms (NENs) differs between organ systems and currently causes considerable confusion. A uniform classification framework for NENs at any anatomical location may reduce inconsistencies and contradictions among the various systems currently in use. The classification suggested here is intended to allow pathologists and clinicians to manage their patients with NENs consistently, while acknowledging organ-specific differences in classification criteria, tumor biology, and prognostic factors. The classification suggested is based on a consensus conference held at the International Agency for Research on Cancer (IARC) in November 2017 and subsequent discussion with additional experts. The key feature of the new classification is a distinction between differentiated neuroendocrine tumors (NETs), also designated carcinoid tumors in some systems, and poorly differentiated NECs, as they both share common expression of neuroendocrine markers. This dichotomous morphological subdivision into NETs and NECs is supported by genetic evidence at specific anatomic sites as well as clinical, epidemiologic, histologic, and prognostic differences. In many organ systems, NETs are graded as G1, G2, or G3 based on mitotic count and/or Ki-67 labeling index, and/or the presence of necrosis; NECs are considered high grade by definition. We believe this conceptual approach can form the basis for the next generation of NEN classifications and will allow more consistent taxonomy to understand how neoplasms from different organ systems inter-relate clinically and genetically.

Unusual Neuroendocrine Differentiation in a Small Round Cell Angiosarcoma: A Potential Histologic Mimicker of Superficial Ewing Sarcoma

Neuroendocrine differentiation or aberrant expression of neuroendocrine markers is very uncommon in angiosarcomas (AS) and creates a challenging differential diagnosis with other superficial or soft tissue tumors. Herein, we report a new case of superficial AS presenting as a tumor lesion on the little finger of the right hand of a 52-year-old man. The tumor displayed CD56, chromogranin-A, and synaptophysin immunoreactivity. Tumor cells were positive for vascular markers (CD31, FLI1, ERG, D2-40, VE-cadherin, VEGR1,2, and 3), CD99, and EMA, but were negative for S100, CK (AE1/AE3), CK20, polyomavirus, and myogenic (desmin and myogenin) and melanocyte markers (melan-A and HMB45). Ki67 immunostains indicated high proliferative activity (>50%). The whole-body computed tomography did not reveal distant disease. The initial assessment considered several tumor subtypes as possible histological diagnoses, including Ewing sarcoma, Ewing-like sarcoma, Merkel cell carcinoma, and undifferentiated "small round cell sarcoma". Fluorescence in situ hybridization analysis was negative for EWSR1 translocation and molecular analysis failed to detect any EWSR1, CIC, SYT or BCOR rearrangement. As a follow-up investigation, we tested 17 cutaneous/superficial AS for neuroendocrine markers; however, only one of these showed focal CD56 and synaptophysin expression. In conclusion, the present findings indicate that neuroendocrine differentiation is a very infrequent feature in AS. We report an AS of the finger with an uncommon histological appearance and immunohistochemical profile: predominant round cell tumor proliferation and neuroendocrine differentiation. Pathologists should be aware of these potential histological and immunohistochemical pitfalls in AS.

Primary low-grade neuroendocrine carcinoma of the skin: An exceedingly rare entity

Low-grade neuroendocrine tumors (NETs), also known as carcinoid tumor, commonly arise from the gastrointestinal (GI) and pulmonary tracts, but rarely occur in the skin. Cutaneous NET typically occurs as metastases or high-grade primary lesions, called Merkel cell carcinoma. In the few cases described in literature, primary low-grade neuroendocrine carcinomas of the skin (LGNECS) are usually indolent cutaneous nodules, presenting on the head and trunk of elderly patients. LGNECS tumors are histologically similar to its counterparts arising in other anatomic locations. As there is no NET cut-off for the skin due to their rarity, the GI scale was used instead; low-grade NETs have a Ki-67 proliferative index of less than 3%. The distinction between primary and metastatic NET, however, is not absolute and can be difficult. A primary vs metastatic NET diagnosis relies on clinical exclusion of a NET in other, more common, anatomic locations. Here, we present a case of an LGNECS on the scalp of a 72-year-old female patient. Whole body imaging failed to identify any octreotide-avid lesions elsewhere in the patient, aside from 2 positive cervical lymph nodes, which were confirmed with a node dissection and histologic evaluation. This is the 19th reported case of LGNECS and the 2nd reported case of LGNECS with nodal metastasis.