Multiple Skin Neoplasms at One Site (MUSK IN A NEST): A Comprehensive Review of Basal Cell Carcinoma and Benign or Malignant "Collision" Tumors at the Same Cutaneous Location

Uncommon Collision Tumors: Dermoscopic and Histopathological Features of Basal Cell Carcinoma Overlying Dermatofibroma

Dermatofibromas (DFs) represent prevalent benign fibrohistiocytic tumors, typically manifesting as solitary lesions. In the majority of cases, the clinical presentation and dermoscopic and histopathological features of DFs adhere to a characteristic profile. However, DFs may exhibit atypical clinical presentations and, more commonly, histologic attributes, posing challenges in differential diagnosis. Both DFs and basal cell carcinomas (BCCs) are frequently encountered cutaneous lesions, each characterized by distinct clinical and dermoscopic features and microscopic morphology. The simultaneous occurrence of these two entities within the same lesion is rare. DFs have been documented to form collision tumors in conjunction with a spectrum of benign and malignant lesions, encompassing not only BCC but also balloon cell nevus, squamous cell carcinoma (SCC), and melanoma. Alterations in the epidermis overlaying a DF range from simple hyperplasia to the proliferation of basaloid cells. Accurate diagnosis, leading to the complete excision of the lesion, is contingent upon the recognition of dermoscopic criteria, precluding misinterpretation as a benign lesion. We present two cases of collision tumors comprising DF and BCC. This case report underscores the paramount importance of dermoscopy and adherence to dermoscopic criteria in the assessment of collision lesions and the diagnostic process related to cutaneous malignancies.

Three Synchronous Non-melanoma Skin Cancers of the Head and Neck: A Case Report and Literature Review

Squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) are the most common non-melanoma skin cancers, with exposure to ultraviolet (UV) light being the most important risk factor. These tumors usually affect older individuals with fair complexions. The co-occurrence of two or more non-melanoma skin cancers is a rare clinical event, the diagnosis of which rests on pathologic examination of the excised tumors. In this study, we report a case of the concurrent occurrence of three non-melanoma skin cancers on the head of a 90-year-old male patient with a history of long-term exposure to UV.

Infiltrative Basal Cell Carcinoma (iBCC) Adjacent to a Desmoplastic Trichoepithelioma (DTE): A Case Report and Literature Review of iBCCs and DTEs

The co-existence of an infiltrative basal cell carcinoma (iBCC) and a desmoplastic trichoepithelioma (DTE) within the same cutaneous lesion is a rare occurrence. iBCCs are relatively common malignant skin neoplasms that pose a risk for local tissue destruction and recurrence. DTEs are cutaneous neoplasms originating from hair follicles that may clinically and histologically appear similar to iBCCs but are ultimately benign. Distinguishing between these two entities is important given their differing destructive potential. Herein, we describe the case of a 36-year-old female with a single skin lesion on her left cheek that was comprised of both an iBCC distinct from a DTE, as verified by histopathologic analysis. A literature review highlights the rarity of such collision tumors and discusses the potential genetic links between these two histologically similar cutaneous neoplasms.

Eccrine Poroma with Concurrent Basal Cell Carcinoma: A Rare Combination

Eccrine poroma (EP) is a benign skin appendicular tumor that differentiates into the terminal sweat duct and is often differentiated from basal cell carcinoma (BCC) and seborrheic keratosis. This report describes a 58-year-old woman who presented with left occipital plaque. Histopathological analysis showed that the tumor cells were located in the lower part of the epidermis. The tumor cells were cuboidal or circular basal-like cells of the same size. The surrounding cells were not arranged in a palisade shape. Scattered tumor clusters composed of basal-like cells were also seen in the dermis, staining basophilic, and the surrounding cells were arranged in a palisade pattern. Immunohistochemistry showed that BerEP4, epithelial membrane antigen EMA, carcinoembryonic antigen CEA, Bcl-2, CD10, CK7 were positive, AR, PAS were negative. According to the pathological examination and immunohistochemical results, a case of eccrine poroma with concurrent basal cell carcinoma was diagnosed.

Combined Mohs Micrographic Surgery in a Collision Tumor

We present the case of a 73-year-old male patient with a collision tumor in the right ear, consisting of a basal cell carcinoma and melanoma in situ. He was managed with Mohs micrographic surgery combining paraffin-embedded sections and frozen sections. Multiple surgical stages were required to obtain tumor-free margins. The surgical defect was reconstructed by plastic surgery, achieving the preservation of the ear. The technique of combining two processing sections is useful in the treatment of the collision of basal cell carcinoma with malignant melanoma.