Assessment of cellular proliferation of eccrine acrospiromas and eccrine sweat gland carcinomas by AgNOR counting and immunohistochemical demonstration of proliferating cell nuclear antigen (PCNA) and Ki-67

Clinicopathological comparison of eccrine poroma and porocarcinoma: Ki-67 index is not a decisive factor

BACKGROUND

Eccrine poroma (EP) and porocarcinoma (EPC) arise from the intraepidermal part of the sweat gland. Clinically they resemble each other and cannot be distinguished without histopathological examination. EPC has been described as aggressive; however, the Ki-67 index is scarcely reported. The aim of this study was to compare clinicopathological factors between EP and EPC with special interest in Ki-67 index.

METHODS AND FINDINGS

50 EP and 22 EPC samples with clinical data from 48 EP and 21 EPC patients were collected from the Finnish Biobanks. We performed immunohistochemistry using a Ki-67 antibody on a tissue microarray and analysed the Ki-67 index with ImmunoRatio 2.5-program. We analysed 48 EP and 21 EPC samples. EPC patients were older (p = 0.019) and their tumours larger (p = 0.003) but other than these there were no statistically significant differences. Ki-67 ratios were similar (medians: EP 0.6% and EPC 0.5%). The median follow-up time in EP group was 12 (range 1.5-30.6 years) and in EPC group 7 years (range 0.75-20.3 years). The survival of EP patients was better than EPC patients but did not reach statistical significance and, in the Cox multivariate analysis only age had statistically significant effect (HR 1.061, 95% CI 1.026-1.099, p < 0.001). Ki-67 index had no statistically significant effect on survival in EPC group in the Cox univariate analysis (HR 0.746, 95% CI 0.390-1.43, p = 0.378).

CONCLUSIONS

EPC patients were older and their tumours larger. There was no difference in Ki-67 index between EP and EPC groups. In the Cox multivariate analysis only age had a statistically significant effect on survival. According to our findings Ki-67 index might not be a decisive factor in the prognosis of EPC. Further studies to validate our current findings are warranted.

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.

Atypical and malignant hidradenomas: a histological and immunohistochemical study

The histological features of atypical hidradenoma are worrisome for increased risk of recurrence and possible malignant potential; however, earlier studies with immunohistochemistry or patient follow-up have not been reported. In addition, immunohistochemical analysis of hidradenocarcinoma exists in the literature mainly as case reports and as a single series of six cases. We compare the histological features and Ki-67, phosphorylated histone H3, epidermal growth factor receptor, and Her2/neu expression profiles of 15 atypical and 15 malignant hidradenomas with those of benign hidradenoma and metastasizing adnexal carcinomas. Infiltrative growth pattern, deep extension, necrosis, nuclear pleomorphism, and > or =4 mitoses per 10 high-power fields are specific features of hidradenocarcinomas. Significant difference in mean Ki-67% was observed between benign and malignant hidradenomas (P<0.001), benign and metastasizing adnexal carcinomas (0.002), atypical and malignant hidradenomas (P<0.001), and between atypical hidradenomas and metastasizing adnexal carcinomas (0.002). Significant difference in mean phosphorylated histone H3% was observed between benign and malignant hidradenomas (P<0.001), benign and metastasizing adnexal carcinomas (0.003), atypical and malignant hidradenomas (P<0.001), and between atypical hidradenomas and metastasizing adnexal carcinomas (P<0.001). Mean epidermal growth factor receptor total score was significantly different in benign and atypical hidradenoma when compared with that in metastasizing adnexal carcinoma (P=0.014 and 0.019, respectively). Equivocal or 2+ Her2/neu positivity was observed in one hidradenocarcinoma and in two metastasizing adnexal carcinomas. Receiver operating characteristic curve analysis for Ki-67 and phosphorylated histone H3% positivity reveals statistically significant criterion values of >11.425 and >0.7, respectively, for distinguishing malignant hidradenomas from atypical hidradenomas. Despite the presence of some worrisome histological features, the significantly different immunoprofile from the malignant counterpart suggests that atypical hidradenomas are likely to recur but are unlikely to metastasize. A tumor with Ki-67>11% and/or phosphorylated histone H3>0.7% would likely be a malignant rather than an atypical hidradenoma. The infrequent Her2/neu overexpression in hidradenocarcinoma suggests its limited therapeutic role.

A single lesion showing features of pigmented eccrine poroma and poroid hidradenoma

Poroid hidradenoma (PH) is a variant of poroma. This entity was defined by Abenoza and Ackerman in 1990. This neoplasm shows architectural characteristics of hidradenoma (tumor cells confined entirely within the dermis in both solid and cystic components) and cytologic characteristics of poroid neoplasm (poroid and cuticular cells, the latter showing ductal differentiation). We herein document a case of single poroid lesion with the features of both eccrine poroma and PH. The patient was a 55-year-old woman with a pigmented nodular lesion on her upper back for 7 years. The histopathologic features of the lesion were consistent with those of eccrine poroma and PH. Unlike most eccrine poromas, this case was pigmented, clinically and microscopically.

[Poroid hidradenoma]

Poroid hidradenoma is a recently described variant of eccrine poroma. This neoplasm presents structural findings of hidradenoma (solid and cystic areas) and cytological characteristics of poromas (poroid and cuticular cells, the latter showing ductal differentiation). We present a case of poroid hidradenoma in a 74-year-old woman, who consulted her physician because of a nodular lesion on the left buttock.

A sweat-gland tumor metastasizing to the axilla: report of a case

Sclerosing sweat-duct carcinoma is a rare malignancy of the skin. We herein present the case of a 68-year-old Japanese man who developed sclerosing sweat-duct carcinoma 2 years after undergoing local excision of a primary tumor in his right arm. Firm nodules appeared in the right axilla, which were revealed by surgical resection to be metastases. This rare tumor grows slowly but usually metastasizes to the regional lymph nodes, whereupon they are often associated with a poor prognosis. As the effectiveness of chemotherapy and radiotherapy against this neoplasm remains unclear, we recommend that the disease should initially be aggressively treated by surgery, which would also be indicated for any metastatic lesions.

Identification of aneuploidy in recurrent clear cell hidradenoma by DNA image cytometry (ICM-DNA)

Since malignant clear cell hidradenoma (CCH) is often characterized by only slight and sometimes by absent nuclear anaplasia, even in metastases, definitive differentiation from its benign counterpart by light microscopy may be very difficult. Herein, we report the case of a 72-year-old woman suffering from a CCH on the back, which showed local recurrence following incomplete excision. By light microscopy no unequivocal signs of malignancy were found either in the primary or the recurrent tumor. However, unusual deep extension to the subcutis with some architectural disorder was seen in the latter. Identification of prospective malignancy in such cases of borderline histopathological features is one of the main indications for diagnostic DNA image cytometry (ICM-DNA). Application of this method to enzymatic cell separation specimens of the recurrence detected marked DNA-aneuploidy with a stemline ploidy of 2.60 c and single events up to 6.7 c, whereas a nearly exact diploid DNA-stemline was found in the primary. We suppose from our results that a prospective malignant CCH with aneuploid DNA-stemline has developed out of its DNA-diploid counterpart. The need for total surgical removal of apparently benign clear cell hidradenomas is further stressed by this observation. Criteria for the diagnosis of malignancy in CCH are reviewed.