Pigmented eccrine poroma of the palm clinically mimicking a seborrheic keratosis

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.

Cryotherapy for Eccrine Poroma: A Case Report

Eccrine poroma (EP) is a benign adnexal tumor that is derived from acrosyringium, the intraepidermal eccrine duct of sweat glands. The standard treatment for eccrine poroma is complete excision. However, this case report highlights cryotherapy as one of the modalities in treating eccrine poroma. We present a case of a 33-year-old male patient who was a known case of generalized vitiligo since he was nine years old. During our skin checkup before starting him on phototherapy, we found a mass over the palmar aspect of the middle finger of the right hand that started to appear five years ago. The mass gradually increased in size, was painless, has no discharge, and was not associated with a history of trauma or infection. The review of systems was unremarkable. Skin examination revealed an asymptomatic, 2.0 × 1.5 cm-sized, solitary, collarette-encircled, dome-shaped, flesh-colored, non-pigmented, deep-red nodule protrusion from the palmar aspect of the middle finger of the right hand. Poroma was considered as the diagnosis, and a punch skin biopsy was performed to confirm the diagnosis and to roll out pyogenic granuloma, amelanotic melanoma, and porocarcinoma as differential diagnoses. A 3 mm punch skin biopsy was performed under local anesthesia and was found to be histologically consistent with eccrine poroma. Hence, cryosurgery was chosen based on histological favorable features. We used cryospray in a single session of 15 seconds in three applications, with five-second intervals in between (skin frosting recovery). Furthermore, the lesion was completely curative with a single session of cryotherapy. The patient followed up for one year without evidence of recurrence.

Pigmented eccrine poroma in an atypical location

Eccrine poroma is the term that includes benign neoplasms of the terminal duct of the eccrine sweat glands, which may clinically and dermoscopically resemble other melanoma and non-melanoma skin tumors. They are often located on the extremities (especially palms and soles), presenting as normochromic or erythematous papules and nodules, measuring up to 2 cm. Pigmented variants are uncommon, accounting for less than 20% of cases. This report describes a 37-year-old man who developed a large pigmented eccrine poroma on his right shoulder, causing diagnostic difficulty. Histopathological examination revealed a nodular neoplasm consisting of small, monomorphic, cuboidal cells, with ample, eosinophilic cytoplasm and well-defined borders, in addition to conspicuous intercellular bridges, with melanin deposits diffusely distributed inside them. The absence of cytological atypia, cellular pleomorphism, increased mitotic activity, and necrosis foci corroborated the diagnostic exclusion of porocarcinoma, which can develop from eccrine poroma.

Morphologic Mimickers of Seborrheic Keratoses: Cutaneous Lesions Masquerading as Seborrheic Keratoses

Seborrheic keratosis is an epithelial-derived benign neoplasm, which presents as a solitary tumor or multiple lesions. It is an acquired skin tumor that is frequently observed in older individuals. Benign neoplasms, as well as premalignant or malignant tumors, can mimic the clinical appearance of a seborrheic keratosis. A man presented with a chronic lesion on his abdomen that had changed in the color and size. The suspected diagnosis was a seborrheic keratosis. However, the microscopic evaluation of a biopsy tissue specimen established a diagnosis of a pigmented squamous cell carcinoma in situ. In addition to squamous cell carcinoma in situ and squamous cell carcinoma, other malignant tumors, premalignant lesions, and benign lesions can mimic a seborrheic keratosis. If a patient presents with a presumptive seborrheic keratosis that has changed in appearance and for which malignancy is also suspected, a biopsy may be helpful for diagnostic clarification to either confirm that the lesion is indeed a seborrheic keratosis or to establish the diagnosis of the lesion that mimics a seborrheic keratosis.