Malignant Melanoma Within Squamous Cell Carcinoma and Basal Cell Carcinoma

Abstract

We report a case of a very unusual combined and collision basosquamous melanocytic malignant tumor on the chest of an 84-year-old man. To our knowledge, this is the first case report describing this entity. We attempt to address the diagnostic challenge and the clinical and histological characteristics of these rare neoplasms with a review of the English literature to further categorize and summarize what has been previously reported about these extraordinary tumors.

Melanoma in situ colonizing basal cell carcinoma: a case report and review of the literature

“…Collision tumors are defined as two distinct neoplasms that occur within close proximity of each other but maintain sharp distinct boundaries [ 1 , 2 ]. Pierard et al retrospectively searched a histopathologic case series of 78,000 primary cutaneous cancers and identified 11 collision tumors of melanoma with BCC [ 3 ].…”

“…Neoplasms consisting of two phenotypically different, yet imperceptibly intertwined populations of malignant cells are referred to as combined tumors [ 1 , 2 , 18 ]. Often immunohistochemical stains are required to appreciate the intermingling of two tumor cell populations.…”

“…Often immunohistochemical stains are required to appreciate the intermingling of two tumor cell populations. Using the above definition, authors have suggested reclassifying some neoplasms previously reported as collision or colonized tumors, as examples of combined BCC and melanoma lesions [ 1 , 2 , 10 , 19 – 30 ].…”

“…The case presented herein represents an example of such a phenomenon ( Table 1 ) [ 32 – 36 ]. Care must be used with the term “colonization” as this term has also been used to describe the situation where large dendritic non-neoplastic melanocytes populate various neoplasms [ 2 , 37 – 39 ]. The discovery of colonization of BCC by melanoma cells specifically led Florell et al to analyze nests of BCC using immunohistochemistry.…”

Collision tumor of bone: primary chondrosarcoma of bone as a rare recipient of tumor-to-tumor metastasis from metastatic breast carcinoma

“…Not only have collision tumors been documented to arise in various anatomic locations, but they have been documented to arise as both benign tumors [9] , benign/malignant tumors [7] and both malignant tumors [5] . Also, collision tumors primarily consist of two colliding tumors, but rare collision tumors consisting of three tumors have been described in the skin [10,12] and uterus [11] as well.…”