Perineural growth of benign cutaneous sweat gland tumors: a hitherto unrecognized phenomenon unassociated with malignancy

Perineural Infiltration: A Comprehensive Review of Diagnostic, Prognostic, and Therapeutic Implications

ABSTRACT

Perineural infiltration refers to a neoplastic cell involvement in, around, and through the nerves. It is considered as one of the neoplastic dissemination pathways. Thus, its identification is crucial to establish the prognosis of some malignant skin neoplasms, such as squamous cell carcinoma, and explains the locally aggressive behavior of cutaneous neoplasms, such as microcystic adnexal carcinoma. We have conducted a review of malignant and benign skin tumors in which perineural infiltration has been described, and we also discuss some histopathological findings that may simulate perineural infiltration.

Solid-Cystic Hidradenoma: A Dorsal Foot Presentation

Solid-cystic hidradenoma is a benign cutaneous tumor with eccrine sweat gland origins that is most commonly found in the head, neck, trunk, and upper extremity regions of patients in the middle to older age groups. These lesions are generally asymptomatic, slow-growing, solitary, and nonulcerative in presentation. Degenerative malignant transformation of this tumor is very rare. In this case report, the authors describe the marginal surgical excision and subsequent microscopic pathologic diagnosis of a moderate sized solid-cystic hidradenoma of the dorsolateral forefoot in a middle-aged male patient.

Epithelial sheath neuroma with extension to the subcutis

Epithelial sheath neuroma (ESN) is a rare entity, histologically showing enlarged nerves in the superficial dermis surrounded by cytologically bland keratinocytes, classically presenting clinically as an erythematous papule or nodule on the back of middle-aged to elderly individuals. Clear-cut recommendations for treatment are not available, with many reports citing biopsy alone or simple excision as curative. We report a case of biopsy-proven ESN presenting as a significantly painful nodule in an elderly woman. Surgical excision was performed for symptom control and the residual ESN was found to extend deep into the subcutis.

Perineural Pseudoinvasion: An Unusual Phenomenon in Nonmalignancies

Perineural invasion (PNI) is characterized as tumoral or nontumoral cells invading in or around the nerves. The neural invasion is considered as a histopathologic characteristic for malignancy and is considered a mechanism for its spread. Both of these patterns usually portend a poor prognosis and very often are markers to prompt additional treatment. There are also some nonmalignancies representing PNI, including benign neoplasms, mimicking lesions, and disorders, such as chronic pancreatitis and endometriosis. The previously recommended terms are PNI, spread, or infiltration. To distinguish PNI in malignancies from that in nonmalignancies, we propose the term "perineural pseudoinvasion" to convey their nonmalignant behavior. Despite the low prevalence, awareness of this benign pseudoinvasion is necessary to avoid aggressive treatment and its misdiagnosis with malignancies. We conducted a systematic search in PubMed and Scopus databases up to December 2015 to find articles reporting PNI in nonmalignancies. After screening, 63 articles were identified as relevant. There were also 2 review articles discussing PNI in nonmalignancies. We aim to present an overview of the perineural pseudoinvasion and to discuss the previously published review articles.