Mimicry Illuminating Pitfalls in Histopathologic Diagnosis: Nutritional Deficiency-Like Dermatitis Secondary to Topical Tazarotene and Keratoacanthomatous Pseudocarcinomatous Hyperplasia in CD30+ Lymphoproliferative Disorder As Illustrative

Pseudocarcinomatous Hyperplasia, Squamous Cell Carcinoma, and Keratoacanthoma Associated to Lymphomas of the Skin and External Mucous Membranes: A Case Report and Literature Review

Pseudocarcinomatous hyperplasia (PCH) is a benign reactive epithelial proliferation that may be associated to lymphomas of the skin or external mucous membranes. We present a case of single lesion mycosis fungoides (Woringer-Kollop's reticulosis pagetoid) associated with PCH that was initially misdiagnosed as squamous cell carcinoma (SCC) and review all PubMed-indexed previously reported cases on lymphomas of the skin or external mucous membranes associated to PCH, SCC, and keratoacanthomas. Including our own case, we collected data of 114 cases of cutaneous or mucosal lymphoproliferative disorders associated to PCH, 3 cases associated to SCC, and other 3 cases associated to keratoacanthomas. All cases were tabulated to the following parameters whenever data was available: sex, age, previous medical conditions, number of lesions (single × multiple), site of involvement (mucosa, skin or both), clinical impression, initial equivocal histopathologic diagnosis, final diagnosis, keratinocytic atypia (presence × absence), lymphocytic atypia (presence × absence), CD30-status, and treatment.

Pseudocarcinomatous Hyperplasia Hiding Lymphomatoid Papulosis

Pseudocarcinomatous hyperplasia (PCH) is a reactive proliferation of the epidermis that can be associated with many inflammatory and neoplastic conditions. Histologically, it is characterized by irregular strands of epidermis, usually at the level of the follicular infundibulum, projecting downward into the dermis. The differentiation between a well-differentiated squamous cell carcinoma and PCH can be particularly challenging when the biopsy is superficial and the causing lesion is dermal-based. Lymphomatoid papulosis (LyP) is an uncommon, self-healing, recurrent, cutaneous T-cell lymphoma, included among the primary cutaneous CD30-positive T-cell lymphoproliferative disorders. LyP is characterized by a chronic course of years to decades that does not compromise survival, even if patients with LyP are at risk for second cutaneous or nodal lymphoid malignancies. LyP and other lymphomas are major neoplastic causes of PCH and can be misdiagnosed or completely overlooked if the PCH is particularly exuberant. We describe the case of an otherwise healthy 55-year-old man who presented with a 3-month history of erythematous papules on upper and lower limbs. A diagnosis of LyP associated with PCH was made after 3 skin biopsies. The propensity of the CD30+ cutaneous lymphoproliferative disorders to an incognito growth pattern is well recognized, and a low-magnification scanning of the histological slides can be an inappropriate approach.

Pseudocarcinomatous hyperplasia in anaplastic large cell lymphoma, a mimicker of poorly differentiated squamous cell carcinoma: report of a case and review of the literature

Pseudocarcinomatous hyperplasia can occasionally be observed in biopsies of CD30-positive lymphoproliferative disorders. It is important to be cognizant of this association, because epithelial hyperproliferation can overshadow large atypical lymphoid cells, leading to an erroneous diagnosis of squamous cell carcinoma (SCC) or keratoacanthoma. Herein, we present a case of anaplastic large cell lymphoma (ALCL) with pseudocarcinomatous hyperplasia simulating a poorly differentiated carcinoma and review the literature on this subject. Immunohistochemical staining with p63 helped delineate the infiltrating tongues of pseudocarcinomatous hyperplasia from the malignant infiltrate. We present this case to raise awareness of the potential for pseudocarcinomatous hyperplasia to occur in the setting of CD30+ lymphoproliferative disorders. Clinicians and dermatopathologists should consider the possibility of ALCL or lymphomatoid papulosis when examining lesions with features of inflamed SCC, especially if the tumor presents on a site or in a patient that is not typical of SCC.

Pseudoepitheliomatous hyperplasia: a review

Pseudoepitheliomatous hyperplasia (PEH) is a benign condition, characterized by hyperplasia of the epidermis and adnexal epithelium, closely simulating squamous cell carcinoma. PEH may be present in a number of conditions characterized by prolonged inflammation and/or chronic infection, as well as in association with many cutaneous neoplasms. Herein, we review different inflammatory, infectious, and neoplastic skin diseases, in which florid epidermal hyperplasia is a prominent histopathologic feature, and introduce a systematic approach in the interpretation of PEH.