Histopathological and immunohistochemical studies of poroid hidradenoma

Reflectance Confocal Microscopy Combined with Dermoscopy and Histology in the Diagnostic Setting of Pigmented Eccrine Poroma: A Retrospective Study

INTRODUCTION

Pigmented eccrine poroma (PEP) is a unique variant of a benign adnexal tumor known as eccrine poroma. Distinguishing PEPs from other pigmented lesions can be challenging due to overlapping clinical and dermoscopic features.

OBJECTIVES

To provide a comprehensive analysis of the dermoscopic, confocal (RCM), and histological features of PEPs.

METHODS

We undertook a retrospective study of the clinical, dermoscopic, RCM and histopathological features of PEPs that were surgically excised and histopathologically recognized. Data on epidemiological, clinical, dermoscopic, RCM and histopathological features were collected from the databases of the Skin Cancer Unit, IRCCS Policlinico di Sant' Orsola, between January 2021 and May 2023.

RESULTS

The study population consisted of 61 patients, including 34 females (55.7%) and 27 males (44.3%). Dermoscopic examination of 61 PEPs revealed the presence of irregular borders (55.7%), milia-like cysts (50.8%), brown pseudo-network (41%), cerebriform pattern (34.4%), comedo-like openings (29.5%), atypical vessels (26.2%), glomerular vessels (18%), fingerprint-like perifollicular structures (8.2%), dots (4.9%) and dotted vessels (4.9%). RCM imaging was collected from 11 cases and showed mostly well-defined tumor nests with small cells in 100% of cases, bright structures in the upper dermis representing melanocytes and melanophages (63.6%), dark round spaces within the tumor nests (54.5%), well-demarcated borders of the nest (45.5%) and dilated and prominent vessels in upper dermis (27.3%). Histopathological pattern analysis revealed PEP sensu stricto (PEPss) as the most frequent (54.1%).

CONCLUSIONS

The distinctive dermoscopic patterns, along with the confocal features aid in the differentiation from other pigmented lesions.

Clinicopathological and genomic copy number variation analysis in nodular hidradenoma and hidradenocarcinoma with focus on prognostically important features

Nodular hidradenoma is a cutaneous adnexal tumor of sweat gland origin, characterized by its diverse but overlapping histomorphologic features with other skin tumors. In addition, distinction of benign hidradenoma and its malignant counterpart hidradenocarcinoma can be challenging, especially in prognostic prediction. We retrospectively reviewed pathological features of 29 cases, including benign nodular hidradenoma (n = 17) and hidradenocarcinoma (n = 12), with clinical follow-up ranging from 18 to 216 months. Genomic copy number variation (CNV) was studied in selected cases (n = 18) by single nucleotide polymorphism microarray. None of the benign hidradenomas (0/17) or low-grade hidradenocarcinomas (0/6) had recurrence or metastasis after complete excision, whereas all 6 high-grade hidradenocarcinomas (6/6) showed locally destructive disease, recurrence, or local metastases. In benign hidradenomas, CNV abnormality was absent in all clear cell hidradenomas (0/5) but was detected in a considerable portion of poroid hidradenoma (3/5), with number of abnormalities ranging 2, 4, and 9. In malignant cases, regardless of morphological classification, both low-grade hidradenocarcinomas demonstrated limited CNV abnormalities in 2 areas (2/2), whereas all high-grade hidradenocarcinomas contained 8 or more CNV abnormalities (6/6). No disease-associated death was recorded in the cohort except one case was lost to follow-up after the development of metastatic disease. Overall, the findings support that genomic CNV abnormalities may serve as a sensitive but less specific tool in detecting malignancy in these tumors, and potentially have a role in predicting clinical behavior particularly in the tumors of nonporoid morphology.

Poroid Hidradenoma: A Two-Case Report and Literature Review

Poroid hidradenoma (PH) is a rare benign tumor that shows differentiation of the eccrine sweat gland. It occurs mainly in adults, presenting as a 0.5 to 2 cm-sized intradermal nodule, mostly on the head, extremities, trunk and neck. We report two rare cases of PH, one on the face and the other on the heel. The first patient was a 50-year-old male who had a solitary, skin-colored nodule on his right temple for 6 months. The second patient was a 67-year-old female who presented with a solitary, bean-sized, tender nodule on her left heel for 1 year. The common histological examination finding was a well-circumscribed tumor composed of solid portions and large cystic spaces in the center. The tumor cells consisted of small, monomorphic poroid cells and large cuticular cells in both cases. To our knowledge, only few cases of PH have been reported. Herein, we report two rare cases of PHs with literature review.

Clinicopathologic Characterization of Hidradenoma on Acral Sites: A Diagnostic Pitfall With Digital Papillary Adenocarcinoma

Hidradenomas are benign sweat gland tumors that typically present as small nodules in adulthood. Their anatomic distribution is wide and rarely includes acral sites. In this setting, reliable separation from digital papillary adenocarcinoma is important, but notoriously difficult. Hematoxylin and eosin-stained sections of 25 hidradenomas on acral skin were retrieved. The clinical presenting features and morphologic findings were recorded, and follow-up was obtained. Immunohistochemistry was performed for AE1/3, CK5/6, EMA, CEA, SMA, S100, p40, and p63. The tumors presented as solitary nodules on the hands (n=17) and feet (n=8) of adults (age range: 20 to 81 y; median: 50 y), with an equal sex distribution. Histologically, the well-circumscribed tumors were lobular, with a solid and cystic growth within dermis. Duct and squamous differentiation and vascularized hyaline stroma were frequent. The majority (n=18) were poroid hidradenomas. Scattered cytologic atypia and mitotic activity (median: 2/10 HPF) were common, and a pseudoinfiltrative growth of strands in a hyaline to sclerotic matrix was noted in 5 tumors. No papillary structures, atypical mitoses, or tumor necrosis were present. Immunohistochemically, all tumors expressed AE1/3, CK5/6, p40, and p63 strongly and diffusely. Luminal differentiation was highlighted by epithelial membrane antigen and carcinoembryonic antigen staining. S100 and SMA staining was absent. Follow-up (1 to 288 mo; median: 61 mo), available for 20 patients, showed no local recurrences and no disease-related mortality. Acral hidradenomas and digital papillary adenocarcinomas share a well-circumscribed dermal growth pattern containing solid, cystic, and tubular areas with mitotic activity and at least focal cytologic atypia. Lack of papillary structures and the diffuse positivity for p40 and p63 in the absence of S100 and SMA expression are helpful features in favor of acral hidradenoma.

Recurrent YAP1-MAML2 and YAP1-NUTM1 fusions in poroma and porocarcinoma

Poroma is a benign skin tumor exhibiting terminal sweat gland duct differentiation. The present study aimed to explore the potential role of gene fusions in the tumorigenesis of poromas. RNA sequencing and reverse transcription PCR identified highly recurrent YAP1-MAML2 and YAP1-NUTM1 fusions in poromas (92/104 lesions, 88.5%) and their rare malignant counterpart, porocarcinomas (7/11 lesions, 63.6%). A WWTR1-NUTM1 fusion was identified in a single lesion of poroma. Fluorescent in-situ hybridization confirmed genomic rearrangements involving these genetic loci. Immunohistochemical staining could readily identify the YAP1 fusion products as nuclear expression of the N-terminal portion of YAP1 with a lack of the C-terminal portion. YAP1 and WWTR1, also known as YAP and TAZ, respectively, encode paralogous transcriptional activators of TEAD, which are negatively regulated by the Hippo signaling pathway. The YAP1 and WWTR1 fusions strongly transactivated a TEAD reporter and promoted anchorage-independent growth, confirming their tumorigenic roles. Our results demonstrate the frequent presence of transforming YAP1 fusions in poromas and porocarcinomas and suggest YAP1/TEAD-dependent transcription as a candidate therapeutic target against porocarcinoma.

Mammographic and ultrasound findings in poroid hidradenoma of the breast mimicking intraductal papilloma and papillary carcinoma: A case report

RATIONALE

Poroid hidradenoma (PH) is a rare variant of benign sweat gland neoplasm without connection to the epidermis. This tumor presents clinically as a solitary lesion with a cystic component located in the subcutaneous layer abutting the skin. On ultrasound, it appears as a circumscribed complex cystic and solid mass abutting the dermis. The occurrence of PH in the breast is very rare. Its features overlap with intraductal papilloma and papillary carcinoma.

PATIENT CONCERNS

A 66-year-old woman presented with a palpable lump in her right breast.

DIAGNOSES

Clinical examination revealed dark bluish dome-shaped nodule which presented as circumscribed round isodense mass on mammography and oval complex cystic and solid mass abutting the dermis on ultrasound. Clinically, a papillary neoplasm was suspected.

INTERVENTIONS

The patient underwent En bloc surgical excision including the overlying epidermis and the surrounding adipose tissue to prevent recurrence.

OUTCOMES

A well-demarcated, non-encapsulated grayish white mass composed of a partly solid and partly cystic area was completely removed and histopathologically confirmed as PH. At the 12-month follow-up, no recurrence was evident.

LESSONS

PH should be considered in the differential diagnosis of a slowly growing breast mass that is bluish, cystic, and solid and abuts the dermis.

A Large Lumbar Adnexal Neoplasm Presenting Characteristics of Eccrine Poroma and Poroid Hidradenoma

Poroma is a rare benign neoplasm that derives from eccrine sweat glands epithelium. Its histological subtypes, with respect to its position within skin layers, are eccrine poroma, hidroacanthoma simplex, poroid hidradenoma, and dermal duct tumor. Poromas commonly exhibit benign clinical behavior as they are usually small and asymptomatic and do not exhibit malignant behavior. Although their histological subtypes share similar histological characteristics, they rarely coexist in the same tumor. In this report we present the case of an unusual poroma in terms of histological and clinical behavior as it was large and presented histological characteristic of both eccrine poroma and poroid hidradenoma. Coexistence of different histologic subtypes in the same tumor indicates simultaneous tumorigenesis, differentiation from one cell type to another, or parallel differentiation from a common progenitor cell. Implications in treatment remain unknown partly due to the rarity of such cases.

Topics in histopathology of sweat gland and sebaceous neoplasms

This article reviews several topics regarding sweat gland and sebaceous neoplasms. First, the clinicopathological characteristics of poroid neoplasms are summarized. It was recently reported that one-fourth of poroid neoplasms are composite tumors and one-fourth are apocrine type lesions. Recent progress in the immunohistochemical diagnosis of sweat gland neoplasms is also reviewed. CD117 can help to distinguish sweat gland or sebaceous tumors from other non-Merkel cell epithelial tumors of the skin. For immunohistochemical differential diagnosis between sweat gland carcinoma (SGC) other than primary cutanesous apocrine carcinoma and skin metastasis of breast carcinoma (SMBC), a panel of antibodies may be useful, including p63 (SGC⁺ , SMBC^- ), CK5/6 (SGC⁺ , SMBC^- ), podoplanin (SGC⁺ , SMBC^- ) and mammaglobin (SGC^- , SMBC⁺ ). Comparison of antibodies used for immunohistochemical diagnosis of sebaceous carcinoma (SC) suggests that adipophilin has the highest sensitivity and specificity. Some authors have found that immunostaining for survivin, androgen receptor and ZEB2/SIP1 has prognostic value for ocular SC, but not extraocular SC. In situ SC is rare, especially extraocular SC, but there have been several recent reports that actinic keratosis and Bowen's disease are the source of invasive SC. Finally, based on recent reports, classification of sebaceous neoplasms into three categories is proposed, which are sebaceoma (a benign neoplasm with well-defined architecture and no atypia), borderline sebaceous neoplasm (low-grade SC; an intermediate tumor with well-defined architecture and nuclear atypia) and SC (a malignant tumor with invasive growth and evident nuclear atypia).

Papillary poroid hidradenoma: a distinct histopathological entity a rare case report

Papillary poroid hidradenoma is a very rare entity which belongs to poroid neoplasms, which represents 10% of sudoriferous tumours. It can be easily misdiagnosed as a malignant neoplasm. A 34-years-old male presented with an asymptomatic mass over the right chest wall, below the nipple, of 18 months duration. Clinical examination revealed tense cystic swelling which revealed hypoechoic and solid components on imaging. Clinically, a malignancy was suspected and a surgical excision was done. Histology and immunoreactivity to pan cytokeratin, epithelial membrane antigen and carcino- embryonic antigen confirmed the diagnosis. We are reporting this case because of the rarity of its presentation.

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.

Facial Apocrine Fibroadenoma in Man: A Rare Finding

Apocrine fibroadenoma (AFA), considered a counterpart of fibroadenoma of breast, is a rare cutaneous apocrine neoplasm occurring almost exclusively in women. We describe a 75-year-old man who presented with a red dome-shaped papule near the nasal bridge. The tumor was composed of numerous tubular, cystic, and partially branching lumina and struts of epithelial cells oriented perpendicular to the skin surface, with which it connected through infundibula. The epithelial strands were embedded in fibrocollagenous stroma. These histopathological features are consistent with AFA. The cytokeratin profiles of our case were similar to those of apocrine or eccrine neoplasms. Progesterone and estrogen receptors (PR/ER) were not expressed. The stroma cells were stained strongly positive for vimentin, but nonreactive for alpha-smooth muscle actin, S-100 protein, or glial fibrillary acidic protein. To the best of our knowledge, this is the first report of facial AFA in man. Different from a more common anogenital AFA, this neoplasm might represent a second type of AFA with unique histopathologic and immunopathological features.