Extramammary Paget's disease mimicking acantholytic squamous cell carcinoma in situ: a case report

Anogenital syringocystadenocarcinoma papilliferum in situ or anaplastic extramammary Paget disease? A unifying concept and review of the literature

Extramammary Paget disease (EMPD) is a rare cutaneous malignancy that typically involves the genital skin and can be primary or associated with an underlying internal malignancy. The typical histopathological appearance of EMPD consists of single or small aggregates of cells with abundant pale cytoplasm and large pleomorphic nuclei, known as Paget cells, scattered throughout the epidermis. We report a case of anogenital EMPD occurring in a 53-year-old man with unusual histopathologic findings of marked epidermal acanthosis, acantholysis, intraepidermal glandular differentiation, and prominent plasma cell-rich fibrovascular cores. These features were entirely confined to the epidermis and adnexa with no evidence of dermal invasion or underlying systemic disease. We review and summarize the literature for atypical features noted in EMPD and summarize similar findings previously described under a variety of descriptions including anaplastic EMPD, anogenital syringocystadenocarcinoma papilliferum in situ (SCACPIS), SCACPIS-like changes in EMPD, and EMPD mimicking acantholytic squamous cell carcinoma in situ. We propose that these features represent a single entity and be considered under a unifying diagnosis to facilitate recognition of this entity.

The Msi1-mTOR pathway drives the pathogenesis of mammary and extramammary Paget's disease

Mammary and extramammary Paget's Diseases (PD) are a malignant skin cancer characterized by the appearance of Paget cells. Although easily diagnosed, its pathogenesis remains unknown. Here, single-cell RNA-sequencing identified distinct cellular states, novel biomarkers, and signaling pathways - including mTOR, associated with extramammary PD. Interestingly, we identified MSI1 ectopic overexpression in basal epithelial cells of human PD skin, and show that Msi1 overexpression in the epidermal basal layer of mice phenocopies human PD at histopathological, single-cell and molecular levels. Using this mouse model, we identified novel biomarkers of Paget-like cells that translated to human Paget cells. Furthermore, single-cell trajectory, RNA velocity and lineage-tracing analyses revealed a putative keratinocyte-to-Paget-like cell conversion, supporting the in situ transformation theory of disease pathogenesis. Mechanistically, the Msi1-mTOR pathway drives keratinocyte-Paget-like cell conversion, and suppression of mTOR signaling with Rapamycin significantly rescued the Paget-like phenotype in Msi1-overexpressing transgenic mice. Topical Rapamycin treatment improved extramammary PD-associated symptoms in humans, suggesting mTOR inhibition as a novel therapeutic treatment in PD.

Syringocystadenocarcinoma Papilliferum In Situ-Like Changes in Extramammary Paget Disease: A Report of 11 Cases

The authors report 11 cases of extramammary Paget disease (EMPD), all of which also demonstrated a combination of histological changes highly reminiscent of syringocystadenocarcinoma papilliferum in situ. In addition to the classical features of EMPD, characterized by the intraepidermal spread of individually dispersed neoplastic cells with ample cytoplasm, many of which contained mucin, there were areas of acanthosis with the substitution of spinous layer keratinocytes by neoplastic cells, whereas the native basal cell layer was intact. In addition to acanthosis (and sometimes papillomatosis), the dermal papillae showed a prominent infiltrate of plasma cells, completing the resemblance to syringocystadenocarcinoma papilliferum in situ; this similarity was further enhanced in 2 cases, which showed conspicuous gland formation. One additional case showed multifocal dermal proliferations compatible with eccrine syringofibroadenoma (syringofibroadenomatous hyperplasia). The changes described herein seem to be relatively rare in EMPD, and they can represent a diagnostic pitfall, as evidenced by 2 cases that were originally misinterpreted as syringocystadenocarcinoma papilliferum in situ. Clinically, these microscopic changes sometimes corresponded to nodular lesions, which were specifically noted to have a papillated erosive surface.

Chemotherapy reaction induced by ixabepilone, a microtubule stabilizing agent, mimicking extramammary Paget's disease in a patient with breast carcinoma

The histopathologic characteristics of reactions caused by the many novel anticancer agents are under-recognized. We report a case of a 67-year-old female with locally advanced metastatic breast cancer, who initially presented with an extensive reticulated erythematous patch on the trunk caused by intravascular metastases confirmed by a skin biopsy. Owing to disease progression, she was started on ixabepilone, a mitotic inhibitor. While receiving ixabepilone, another skin biopsy was obtained and initially interpreted as extramammary Paget's disease. However, the biopsy showed metaphase arrest of numerous keratinocytes in the basilar and suprabasilar epidermis. Atypical epithelial cells were only present in the intravascular spaces similar to the initial biopsy. Given the temporal association between the initiation of ixabepilone therapy and the epidermal mitotic arrest, a diagnosis of chemotherapy reaction to ixabepilone was rendered. Ixabepilone is an analog of epothilone, a microtubule stabilizer causing mitotic arrest of the cell cycle approved for the treatment of metastatic and locally advanced treatment-resistant breast cancer. The demonstration of epidermal mitotic arrest caused by ixabepilone is without precedent. The case emphasizes the importance of considering a chemotherapy reaction in the histologic differential diagnosis of epidermal mitotic arrest in a cancer patient receiving chemotherapy.

Diagnostic Immunohistochemistry in Cutaneous Neoplasia: An Update

Immunohistochemistry (IHC) is an important adjunct in the diagnosis of neoplastic skin diseases. In addition to the many established IHC markers currently in use, new markers continue to emerge, although their general acceptance and routine application requires robust validation. Here, we summarize the most well-established and commonly used biomarkers along with an array of newer ones reported in the past several decades that either demonstrate or hold high clinical promise in the field of cutaneous pathology. We also highlight recent applications of novel IHC markers in melanoma diagnosis including genetic mutation status markers [e.g. BRAF (v-raf murine sarcoma viral oncogene homolog B) and NRAS (neuroblastoma RAS viral oncogene homolog)] and an epigenetic alteration marker (e.g. 5-hydroxymethylcytosine). We specifically focus on the role of IHC in the differential diagnosis of cutaneous lesions that fall under the following categories: melanoma, epidermal tumors with an intraepidermal epitheliomatous pattern, spindle cell lesions of the dermis, small round blue cell tumors of the dermis, and cutaneous adnexal tumors. While IHC is a valuable tool in diagnostic dermatopathology, marker selection and interpretation must be highly informed by clinical context and the histologic differential diagnosis. With rapid progress in our understanding of the genetic and epigenetic mechanisms of tumorigenesis, new IHC markers will continue to emerge in the field of diagnostic dermatopathology.

Squamous cell carcinoma of the scrotum: A look beyond the chimneystacks

Despite the low incidence, squamous cell carcinoma (SCC) remains the most common scrotal malignancy with a propensity for recurrence and metastasis. In recent years there has been a significant change in the epidemiology of scrotal SCC. Surgery is the mainstay of treatment for resectable disease. Sentinel lymph node dissection adapted from experience with penile SCC can reduce the morbidity of routine lymph node dissection. Emerging treatments for advanced and metastatic SCC are at the cusp of significantly changing management of this disease. We have performed a comprehensive review of scrotal SCC with a focus on these topics.

Positive KI67 and periodic acid-schiff mandates wider range of excision in scrotal extramammary Paget's disease

BACKGROUND

Extramammary Paget's disease (EMPD) of the scrotum is a rare disease that requires surgical excision. A positive margin is related to recurrence and poorer prognosis. We aimed to investigate the expression of Ki67 and periodic acid-Schiff (PAS) in a biopsy sample and to evaluate their predictive value in true margin status.

METHODS

Sixty-four patients with noninvasive scrotal EMPD were included. Immunohistochemical staining of Ki67 and PAS was reviewed and compared statistically with the margin status of intraoperative frozen section examination (FSE).

RESULTS

Seventeen of 64 patients had a positive margin discovered at the first FSE. Expression of Ki67 was not significantly different between positive and negative margin status (p = .16). Expression of PAS was higher in samples with positive margins (p = .05). The incidence of positive margins was significantly higher in the double-positive group than in the double-negative group (p = .03).

CONCLUSION

Positive expression of both factors in a biopsy sample requires wider excision to ensure negative margins.

Recurrent trichilemmal carcinoma with a large cutaneous horn formation

We describe an unusual case of trichilemmal carcinoma accompanied by a large horn formation in a 79-year-old man who presented with a brown tumor mass including a 15-cm-long horn on the vertex for one and a half years. Two months after the surgical removal of the primary tumor, the tumor recurred with a dimension 10x8x8 cm. The tumor was then excised again and the wound was covered using skin from the patient's back. Microscopically, the tumor showed histology consistent with trichilem¬mal carcinoma. After 2 years, the patient had not shown any recurrence or metastases. We highlight the features that distinguish trichilemmal carcinoma from the other malignant tumors, such as squamous cell carcinoma, basal cell carcinoma, nodular melanoma, or keratoacanthoma.