Abstract
Although malignant melanoma (MM) and both basal cell carcinoma (BCC) and actinic keratosis (AK) are sun-induced lesions, the coexistence of these entities at the same anatomical site (collision tumour) is exceedingly rare. We report the case of a 54-year-old woman with a known history of xeroderma pigmentosum variant (XPV) who presented with 2 separate skin lesions over the middle and upper right forearm, respectively. The clinical impression was that of BCCs or squamous cell lesions. On histological examination, both specimens showed features of melanoma in situ (MIS). In the first lesion, MIS merged with and colonised a superficial and focally invasive BCC. In the second lesion, MIS merged with an AK. No separate invasive nests of malignant melanoma were seen in either specimen. The atypical melanocytes were highlighted by Melan-A and HMB-45 immunostaining, whereas the epithelial cells in both the BCC and AK stained with the pancytokeratin MNF-116. The patient had a previous history of multiple MMs and non-melanomatous skin cancers and finally developed widespread metastatic malignant melanoma, which proved fatal. The rare and interesting phenomenon of collision tumours may pose diagnostic difficulties. To our knowledge, this is the first reported simultaneous presentation of cytologically malignant collision tumours in a patient with XPV.
Highlights
The co-existence of two or more histologically distinct neoplasms arising from different cell lines resulting in a single cutaneous lesion, so-called collision or combined lesion, is relatively rare but well-described in the literature
The collision is between basal cell carcinoma (BCC) and benign naevus; BCC and seborrhoeic keratosis (SK) or SK and benign naevus.[1]
We report a rare case of two simultaneous, cytologically malignant collision lesions in a patient with xeroderma pigmentosum variant (XPV)
Summary
The co-existence of two or more histologically distinct neoplasms arising from different cell lines resulting in a single cutaneous lesion, so-called collision or combined lesion, is relatively rare but well-described in the literature. A 54-year-old white female XPV patient under regular Dermatology review and who frequently attended a combined Plastic Surgery and Dermatology Clinic developed two new cutaneous lesions on the right middle and upper forearm. Both were clinically suspected as squamous cell lesions or BCCs and she proceeded to excision biopsies. This lesion was classified as a collision lesion (intermingled type) of AK and MIS. The patient had a past medical history of multiple other solar-related cutaneous neoplasms including BCCs, MMs and squamous cell carcinomas (SCC) over the preceding 30 years. One year after excision of the collision lesions, the patient developed metastatic malignant melanoma to the lung and subsequently to the pelvis, which proved fatal
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