Basal Cell Carcinoma and Squamous Cell Carcinoma in a Single Lesion on the Forehead: A Rare Case of Collision Tumor in a Patient with Albinism

Ugwo Ifeanyi, V.¹, Ojo Babarinde, A.^2*, Ojo Oluwatomide, N.³, Umobong Emanso⁴, Eke Barnabas, A.⁵, Efu, E. M.⁶, Inemesit David, E.⁷

¹Department of Anatomic Pathology, National Orthopedic Hospital, Enugu, Nigeria
²Department of Anatomic Pathology, College of Health Sciences, Benue State University, Makurdi, Nigeria
³McMaster University, Hamilton, Ontario, Canada
⁴Histoconsult Laboratory, Abuja, Nigeria
⁵Department of Surgery, College of Health Sciences, Benue State University, Makurdi, Nigeria
⁶Department of Anaesthesia, College of Health Sciences, Benue State University, Makurdi, Nigeria
⁷Screenics Pathology Solutions, Ondo, Nigeria

*Correspondence to: Dr. Ojo Babarinde, A., Department of Anatomic Pathology, College of Health Sciences, Benue State University, Makurdi, Nigeria.

Copyright © 2023 Dr. Ojo Babarinde, A., et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Introduction
A collision tumor is a neoplastic lesion comprised of two or more distinct cell populations that maintain distinct borders [1]. It is a combination of two types of tumors in a single lesion [2]. They are rare, but well documented and can be composed either of two benign tumors, a benign and malignant tumor, or two malignant tumors. Their diagnosis is often incidental, and their behavior remains widely unknown with several theories proposed regarding their pathogenesis [3]. Collision tumors rarely occur in the skin. We report the rare occurrence of squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) [4] in a single tumor on the forehead of a 40 years-old albino female patient with a review of the literature.

Case Presentation
A 40 years-old female albino patient presented with recurrent forehead ulcer. It started about 10 years ago as a small lesion about 3x2cm in diameter. It was excised without any histopathologic diagnosis about a year ago. She presented with a spherical-shaped ulcer on the left side of the forehead with patchy necrotic tissues measuring 10x12cm with a sloppy edge. She had an excision done with scalp reconstructions at surgery and transfused with 2 units of parked red blood cells. She had a left forehead graft and was on alternate-day graft dressing with sufratule after then. At surgical pathology, the specimen consists of a markedly ulcerated skin tissue measuring 10x10cm. The edges of the ulcer were not well delineated.

The histopathologic examination (Fig, 1, 2, 3,4) shows a malignant neoplastic lesion composed of proliferating squamous cells interposed by keratin pearls. Focal areas show basaloid cells with peripheral palisading and retraction artefacts invading and distorting the adjacent tissues, provoking inflammation reactions. The borders between these two distinct histology formations are distinct. Based on these histological findings a diagnosis of a collision tumor consisting of squamous cell carcinoma and based cell carcinoma was made.

The tumor cells resulted immunoreactive for S-100 protein (Fig 2,). The post-operative phase was uneventful and was discharged home on postoperative day six and was seen a week after discharge

Discussion
A collision tumor which represents a combination of two tumors in a single lesion has a pathogenesis that is still a matter of speculation. One of the hypotheses includes one tumor inducing epithelial or stromal changes to develop the second tumor [5]. They rarely occur in the skin and in particular, the combination of SCC and BCC occurs seldomly.

It is important to differentiate SCC and BSC as collision tumors from baso-squamous carcinoma (BSC). BSC is defined as a tumor containing the areas of both BSC and SCC with a transition zone linking the two [6]. On the other hand, there is a distinct demarcation between the two components of the collision tumor. Albinism is an inherited disorder of hypopigmentation involving the skin, eyes, and hair because of the absence or defect in tyrosinase enzyme which converts tyrosine to dioxyphenylalanine, the pressures of melanin [7]. Because of the reduction or absence of melanin, albinos are very sensitive to the harmful effects of ultraviolet (UV) light and are at more risk of actinic lesions and dermatoses, the most worrying of which is precancerous and cancerous lesions [7,8]. African albinos are more prone to having cutaneous cancers because they live close to the equator where the exposure to ultraviolet radiation of the sun is much higher compared to Caucasian albinos (9). The most frequent cancer in these patients is SCC [9-12]. This is followed by BCC [9].

Basal cell carcinoma, non-melanocytic skin cancer is the most common skin cancer and constitutes about 80% worldwide [13]. They are rare in dark-skinned races. Squamous cell carcinoma is the second most common form of skin cancer worldwide. In Nigeria, malignant melanoma ranked highest as the most common skin cancer followed by SCC, dermato-fibrosarcoma, and BCC respectively [14]. These cancers, BCC and SCC are most often found in areas exposed to the sun, such as the head, neck, and arms, but can also occur elsewhere. The collision malignancy in our case was found on the forehead. Our search through the literature did not reveal the BCC SCC and BCC occurrence in any patient with albinism.

It is not entirely uncommon for a BCC to develop alongside another cutaneous neoplasm [15]. The most reported combination of skin tumors is that of BCC and a melanocytic nevus [16]. An individual presenting with a BCC and SCC of the palm at the same time was also reported [15], though a rare occurrence. Cutaneous collision tumors are defined as two independent tumors anatomically close yet separated by a well-defined boundary [17].

Conclusion
An individual presenting with a BCC and SCC of the skin concurrently is rare, and to our knowledge, a collision tumor of both entities of the forehead in a patient with albinism has not been described in the literature. Various postulates exist for collision tumors, while others theorize it to be purely coincidental.

Fundings
No funding was received for this study.

Disclosures
The authors have no conflicts of interest relevant to the content of this article.

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