Understanding Pseudoepitheliomatous Hyperplasia:

Diagnostic Challenges during Inflammation and Cancer: Current Biomarkers and Future Perspectives in Navigating through the Minefield of Reactive versus Dysplastic and Cancerous Lesions in the Digestive System

In the setting of pronounced inflammation, changes in the epithelium may overlap with neoplasia, often rendering it impossible to establish a diagnosis with certainty in daily clinical practice. Here, we discuss the underlying molecular mechanisms driving tissue response during persistent inflammatory signaling along with the potential association with cancer in the gastrointestinal tract, pancreas, extrahepatic bile ducts, and liver. We highlight the histopathological challenges encountered in the diagnosis of chronic inflammation in routine practice and pinpoint tissue-based biomarkers that could complement morphology to differentiate reactive from dysplastic or cancerous lesions. We refer to the advantages and limitations of existing biomarkers employing immunohistochemistry and point to promising new markers, including the generation of novel antibodies targeting mutant proteins, miRNAs, and array assays. Advancements in experimental models, including mouse and 3D models, have improved our understanding of tissue response. The integration of digital pathology along with artificial intelligence may also complement routine visual inspections. Navigating through tissue responses in various chronic inflammatory contexts will help us develop novel and reliable biomarkers that will improve diagnostic decisions and ultimately patient treatment.

Immune-Checkpoint Induced Skin Toxicity Masked as Squamous Cell Carcinoma: Case Report on Mimickers of Dermatological Toxicity with PD-1 Inhibition

BACKGROUND

Immune checkpoint inhibitors (ICI) are increasingly the mainstay of oncology treatment. Immune-related adverse events (irAEs) from ICI therapy differ from cytotoxic adverse events. Cutaneous irAEs are one of the most common irAEs and require careful attention to optimize the quality of life for oncology patients.

PATIENT AND METHODS

These are two cases of patients with advanced solid-tumour malignancies treated with PD-1 inhibitor therapy.

RESULTS

Both patients developed multiple pruritic hyperkeratotic lesions, which were initially diagnosed as squamous cell carcinoma from skin biopsies. The presentation as squamous cell carcinoma was atypical and, upon further pathology review, the lesions were more in keeping with a lichenoid immune reaction stemming from the immune checkpoint blockade. With the use of oral or topical steroids and immunomodulators, the lesions resolved.

CONCLUSIONS

These cases emphasize that patients on PD-1 inhibitor therapy who develop lesions resembling squamous cell carcinoma on initial pathology may require an additional pathology review to assess for immune-mediated reactions, allowing appropriate immunosuppressive therapy to be initiated.

Cutaneous Pseudoepitheliomatous Hyperplasia from a Displaced Metallic Orthopedic Implant

While rare, cutaneous SCC in patients with darker Fitzpatrick skin types is essential to identify and investigate early and can have a myriad of clinical presentations. While clinical history-taking of suspicious skin lesions is often symptom-driven, other key patient history components, such as surgical history, are often overlooked. Differentiating, prioritizing, and risk-stratifying hyperkeratotic, verrucous papules in patients with darker Fitzpatrick skin types is an essential clinical skill for clinicians to develop to serve an increasingly diverse patient population. This original report presents the case of a displaced orthopedic screw causing pseudoepitheliomatous hyperplasia that was initially misdiagnosed as squamous cell carcinoma. This case highlights the importance of careful consideration of surgical history, choice of biopsy method, and skin type when examining lesions concerning for squamous cell carcinoma.

Marjolin's ulcer of the hallux

We report the case of a 51-year-old woman with malignant degeneration of a right hallux nail bed ulcer of 20 years' duration. Histologic examination confirmed the diagnostic features of Marjolin's ulcer, a well-defined but uncommon malignant ulcer that occurs in chronic wounds and cutaneous scars. In this report, we describe the clinical and histopathologic features and the differential diagnosis of this unusual lesion.

Verrucous hemangioma with pseudoepitheliomatous epidermal hyperplasia in an adult horse

Verrucous hemangiomas are a rare specific variant of equine skin tumors not well described in the literature. An 8-year-old gelding presented a unilateral lesion on the pastern. Macroscopically, the mass showed a warty and verrucous surface with focal ulcerations. The histology showed a dermal proliferation of endothelial-layered capillaries and venules separated by a delicate stroma of scant fibroblasts and collagen deposition, with pseudoepitheliomatous hyperplasia (exuberant reactive irregular epithelial hyperplasia with tongue-like projections extending into the dermis, mimicking downgrowth of squamous cell carcinoma) and orthokeratotic hyperkeratosis of the overlying epidermis. The immunohistochemical study confirmed the endothelial origin of the tumor, and a final diagnosis of verrucous hemangioma with pseudoepitheliomatous hyperplasia was confirmed. To the knowledge of the authors, this is the first detailed description of this entity in adult horses. Moreover, the clinical progression and epidermal changes have not been previously reported, emphasizing the importance of a pathological study of any epithelial preneoplastic lesion to rule out an underlying dermal neoplasia.

Expression of laminin-5 γ2 chain in cutaneous pseudocarcinomatous hyperplasia

BACKGROUND

Since the use of laminin-5 as a marker of invasiveness has been proposed by several authors, our objective was to compare the expression of this protein in pseudocarcinomatous hyperplasia and squamous cell carcinoma (SCC).

METHODS

Sixty-four paraffin-embedded skin biopsy samples with diagnosis of epidermal hyperplasia (non-pseudocarcinomatous), pseudocarcinomatous hyperplasia, actinic keratosis/carcinoma in situ, microinvasive and frankly invasive SCC were obtained for immunohistochemical study.

RESULTS

Adjacent normal epithelium and epidermal hyperplasia (non-pseudocarcinomatous) showed no staining. In pseudocarcinomatous hyperplasia, laminin-5 was positive, at least focally, in 14 of 16 (87.5%) samples and was concentrated in peripheral cells of elongated rete pegs and in migrating cells in dermis. In samples of microinvasive carcinoma (n = 7), the expression was observed in all cases and was concentrated in the leading edge of the tumor. All cases (n = 21) of frankly invasive SCC showed cells expressing laminin-5, at least focally. Well-differentiated areas of the tumor presented a pattern of expression in peripheral cells of tumor nests while a diffuse pattern of expression was observed in less differentiated areas.

CONCLUSION

We showed that cytoplasmic laminin-5 expression should not be used as a criterion of malignancy and is not useful in distinguishing pseudocarcinomatous hyperplasia from microinvasive and well-differentiated SCC.

Marjolin ulcer: an overlooked entity

Marjolin ulcer is a well-defined, but uncommon malignant ulcer that occurs in chronic wounds and cutaneous scars. Jean-Nicolas Marjolin was credited with describing this phenomenon in 1828. This entity is frequently overlooked and therefore inadequately treated leading to a poor prognosis. The malignant transformation of an ulcer is most commonly associated with burn scars, but has been reported in many other types of chronic, non healing wounds such as traumatic wounds, venous stasis and chronic pressure ulcers, fistulas, lacerations and leprosy ulcers. Development of malignancy tends to be slow with an average time of approximately 25 years. Various theories concerning pathogenesis of Marjolin ulcer have been proposed. Well-differentiated squamous cell carcinoma (SCC) is the most common histological type of Marjolin ulcer. Biopsy with histopathologic interpretation remains the gold standard for the diagnosis, with radical surgical excision being the treatment of choice. A high index of suspicion should be held by any health care provider when evaluating a chronic, non healing wound. This is a case report of a Marjolin ulcer arising on the left buttock of a patient with a long-standing history of a traumatic wound.